scope of the literature review

• Research guides

Writing a Literature Review

Phase 1: scope of review, it's a literature review of what, precisely.

Need to Have a Precise Topic It is essential that one defines a research topic very carefully. For example, it should not be too far-reaching. The following is much too broad:

"Life and Times of Sigmund Freud"

However, this is more focused and specific and, accordingly, a more appropriate topic:

"An Analysis of the Relationship of Freud and Jung in the International Psychoanalytic Association, 1910-1914"

Limitations of Study In specifying precisely one's research topic, one is also specifying appropriate limitations on the research. Limiting, for example, by time, personnel, gender, age, location, nationality, etc. results in a more focused and meaningful topic.  

Scope of the Literature Review It is also important to determine the precise scope of the literature review. For example,

• What exactly will you cover in your review?
• How comprehensive will it be?
• How long? About how many citations will you use?
• How detailed? Will it be a review of ALL relevant material or will the scope be limited to more recent material, e.g., the last five years.
• Are you focusing on methodological approaches; on theoretical issues; on qualitative or quantitative research?
• Will you broaden your search to seek literature in related disciplines?
• Will you confine your reviewed material to English language only or will you include research in other languages too?

In evaluating studies, timeliness is more significant for some subjects than others. Scientists generally need more recent material. However, currency is often less of a factor for scholars in arts/humanities. Research published in 1920 about Plato's philosophy might be more relevant than recent studies.

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• Last Updated: Dec 5, 2023 2:26 PM
• Subjects: Education , General
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Writing a literature review.

• Definitions

Determine the scope of your review

A review of what, planning your literature review.

• Finding sources
• Annotating sources
• Organizing the review
• Writing the review
• Practical Tips

The length of the review depends on your objective. 

• Are you writing a research paper as the final project in a specific course?
• Are you writing a senior or honor's capstone project or thesis? 
• Are you writing for an undergraduate or graduate course? 
• Are you writing a master's thesis? 
• Are you writing a dissertation?

The majority of these projects will require a selective examination of the literature.  Discuss the length of your review with your instructor or paper advisor.

• You must have a precise question to study. For example, your question cannot be too broad, nor too narrow. 
• You must understand the limitations of your research. Limiting by time, geographic area, gender, age, and/or nationality are all good ways to develop a more focused topic.
• what will you cover?
• will your coverage be selective or exhaustive?
• are you focusing on a specific theory or methodology; a specific type of research?
• will you include information published in other languages?
• will you include information from related disciplines?

It will take time to locate and review the literature relevant to your research question.  Starting early will allow you sufficient time to gather and review your sources.  The process of writing a literature review normally includes the following elements:

1. Defining your research question

2. Planning the approach to your review and research

3. Searching the literature

4. Analyzing the material you find

5. Organizing the review

6. Writing the review

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Literature review.

• Introduction to Literature Reviews
• Purpose and Scope
• Types of Lit Reviews
• Finding Published Literature Reviews
• Writing the Lit Review
• Books and Websites

The literature review analyzes relationships and connections among different works. This differs from an annotated bibliography which provides a list and brief description of articles, books, theses, and other documents. The literature review should not merely list and summarize one piece of research after another. 

Through analysis of major works and subsequent scholarship the lit review lays out the evolution of scholarship on a topic and establishes a context for further research. This will help you to establish why the topic is important and place your research in a theoretical context.

A literature review will help you to avoid redundancy in your own research and to identify new problems, possibilities for further research, and to expand upon or ask new questions. The literature review allows you as a researcher to enter into an ongoing conversation with other scholars and researchers.

A literature review may be comprehensive or selective but should examine seminal or principal works and works that have been consequential in the field. The scope of a literature review will vary by assignment and discipline. The literature review may be part of a larger work or a stand-alone article, meaning that it is the entirety of a paper. The literature review may be part of the introduction, or a separate section to a thesis, dissertation, or research report setting up the context for the author's original research.   The literature review:

• Compares and contrasts
• Identifies areas of consensus and dissent
• Reveals gaps or oversights
• Indicates areas needing further research
• Points out trends, themes, approaches, methodologies, theories, and frames of analysis
• Discusses major debates in the field
• Examines methodological or theoretical strengths and weaknesses

The importance of currency (timeliness of information) will vary by discipline and the purpose of the assignment. The sciences are typically more concerned with current research, practice, and findings. For example, in fields like health or medicine the lit review may only draw on recent literature which has been published within 5-10 years. However, inclusion of much older works is often relevant in fields such as the arts, humanities, philosophy, or history.

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Methodology

• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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How To Structure Your Literature Review

3 options to help structure your chapter.

By: Amy Rommelspacher (PhD) | Reviewer: Dr Eunice Rautenbach | November 2020 (Updated May 2023)

Writing the literature review chapter can seem pretty daunting when you’re piecing together your dissertation or thesis. As  we’ve discussed before , a good literature review needs to achieve a few very important objectives – it should:

• Demonstrate your knowledge of the research topic
• Identify the gaps in the literature and show how your research links to these
• Provide the foundation for your conceptual framework (if you have one)
• Inform your own  methodology and research design

To achieve this, your literature review needs a well-thought-out structure . Get the structure of your literature review chapter wrong and you’ll struggle to achieve these objectives. Don’t worry though – in this post, we’ll look at how to structure your literature review for maximum impact (and marks!).

But wait – is this the right time?

Deciding on the structure of your literature review should come towards the end of the literature review process – after you have collected and digested the literature, but before you start writing the chapter. 

In other words, you need to first develop a rich understanding of the literature before you even attempt to map out a structure. There’s no use trying to develop a structure before you’ve fully wrapped your head around the existing research.

Equally importantly, you need to have a structure in place before you start writing , or your literature review will most likely end up a rambling, disjointed mess. 

Importantly, don’t feel that once you’ve defined a structure you can’t iterate on it. It’s perfectly natural to adjust as you engage in the writing process. As we’ve discussed before , writing is a way of developing your thinking, so it’s quite common for your thinking to change – and therefore, for your chapter structure to change – as you write. 

Need a helping hand?

Like any other chapter in your thesis or dissertation, your literature review needs to have a clear, logical structure. At a minimum, it should have three essential components – an  introduction , a  body   and a  conclusion . 

Let’s take a closer look at each of these.

1: The Introduction Section

Just like any good introduction, the introduction section of your literature review should introduce the purpose and layout (organisation) of the chapter. In other words, your introduction needs to give the reader a taste of what’s to come, and how you’re going to lay that out. Essentially, you should provide the reader with a high-level roadmap of your chapter to give them a taste of the journey that lies ahead.

Here’s an example of the layout visualised in a literature review introduction:

Your introduction should also outline your topic (including any tricky terminology or jargon) and provide an explanation of the scope of your literature review – in other words, what you  will   and  won’t   be covering (the delimitations ). This helps ringfence your review and achieve a clear focus . The clearer and narrower your focus, the deeper you can dive into the topic (which is typically where the magic lies). 

Depending on the nature of your project, you could also present your stance or point of view at this stage. In other words, after grappling with the literature you’ll have an opinion about what the trends and concerns are in the field as well as what’s lacking. The introduction section can then present these ideas so that it is clear to examiners that you’re aware of how your research connects with existing knowledge .

2: The Body Section

The body of your literature review is the centre of your work. This is where you’ll present, analyse, evaluate and synthesise the existing research. In other words, this is where you’re going to earn (or lose) the most marks. Therefore, it’s important to carefully think about how you will organise your discussion to present it in a clear way. 

The body of your literature review should do just as the description of this chapter suggests. It should “review” the literature – in other words, identify, analyse, and synthesise it. So, when thinking about structuring your literature review, you need to think about which structural approach will provide the best “review” for your specific type of research and objectives (we’ll get to this shortly).

There are (broadly speaking)  three options  for organising your literature review.

Option 1: Chronological (according to date)

Organising the literature chronologically is one of the simplest ways to structure your literature review. You start with what was published first and work your way through the literature until you reach the work published most recently. Pretty straightforward.

The benefit of this option is that it makes it easy to discuss the developments and debates in the field as they emerged over time. Organising your literature chronologically also allows you to highlight how specific articles or pieces of work might have changed the course of the field – in other words, which research has had the most impact . Therefore, this approach is very useful when your research is aimed at understanding how the topic has unfolded over time and is often used by scholars in the field of history. That said, this approach can be utilised by anyone that wants to explore change over time .

For example , if a student of politics is investigating how the understanding of democracy has evolved over time, they could use the chronological approach to provide a narrative that demonstrates how this understanding has changed through the ages.

Here are some questions you can ask yourself to help you structure your literature review chronologically.

• What is the earliest literature published relating to this topic?
• How has the field changed over time? Why?
• What are the most recent discoveries/theories?

In some ways, chronology plays a part whichever way you decide to structure your literature review, because you will always, to a certain extent, be analysing how the literature has developed. However, with the chronological approach, the emphasis is very firmly on how the discussion has evolved over time , as opposed to how all the literature links together (which we’ll discuss next ).

Option 2: Thematic (grouped by theme)

The thematic approach to structuring a literature review means organising your literature by theme or category – for example, by independent variables (i.e. factors that have an impact on a specific outcome).

As you’ve been collecting and synthesising literature , you’ll likely have started seeing some themes or patterns emerging. You can then use these themes or patterns as a structure for your body discussion. The thematic approach is the most common approach and is useful for structuring literature reviews in most fields.

For example, if you were researching which factors contributed towards people trusting an organisation, you might find themes such as consumers’ perceptions of an organisation’s competence, benevolence and integrity. Structuring your literature review thematically would mean structuring your literature review’s body section to discuss each of these themes, one section at a time.

Here are some questions to ask yourself when structuring your literature review by themes:

• Are there any patterns that have come to light in the literature?
• What are the central themes and categories used by the researchers?
• Do I have enough evidence of these themes?

PS – you can see an example of a thematically structured literature review in our literature review sample walkthrough video here.

Option 3: Methodological

The methodological option is a way of structuring your literature review by the research methodologies used . In other words, organising your discussion based on the angle from which each piece of research was approached – for example, qualitative , quantitative or mixed  methodologies.

Structuring your literature review by methodology can be useful if you are drawing research from a variety of disciplines and are critiquing different methodologies. The point of this approach is to question  how  existing research has been conducted, as opposed to  what  the conclusions and/or findings the research were.

For example, a sociologist might centre their research around critiquing specific fieldwork practices. Their literature review will then be a summary of the fieldwork methodologies used by different studies.

Here are some questions you can ask yourself when structuring your literature review according to methodology:

• Which methodologies have been utilised in this field?
• Which methodology is the most popular (and why)?
• What are the strengths and weaknesses of the various methodologies?
• How can the existing methodologies inform my own methodology?

3: The Conclusion Section

Once you’ve completed the body section of your literature review using one of the structural approaches we discussed above, you’ll need to “wrap up” your literature review and pull all the pieces together to set the direction for the rest of your dissertation or thesis.

The conclusion is where you’ll present the key findings of your literature review. In this section, you should emphasise the research that is especially important to your research questions and highlight the gaps that exist in the literature. Based on this, you need to make it clear what you will add to the literature – in other words, justify your own research by showing how it will help fill one or more of the gaps you just identified.

Last but not least, if it’s your intention to develop a conceptual framework for your dissertation or thesis, the conclusion section is a good place to present this.

Example: Thematically Structured Review

In the video below, we unpack a literature review chapter so that you can see an example of a thematically structure review in practice.

Let’s Recap

In this article, we’ve  discussed how to structure your literature review for maximum impact. Here’s a quick recap of what  you need to keep in mind when deciding on your literature review structure:

• Just like other chapters, your literature review needs a clear introduction , body and conclusion .
• The introduction section should provide an overview of what you will discuss in your literature review.
• The body section of your literature review can be organised by chronology , theme or methodology . The right structural approach depends on what you’re trying to achieve with your research.
• The conclusion section should draw together the key findings of your literature review and link them to your research questions.

If you’re ready to get started, be sure to download our free literature review template to fast-track your chapter outline.

Psst… there’s more!

This post is an extract from our bestselling Udemy Course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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27 Comments

Great work. This is exactly what I was looking for and helps a lot together with your previous post on literature review. One last thing is missing: a link to a great literature chapter of an journal article (maybe with comments of the different sections in this review chapter). Do you know any great literature review chapters?

I agree with you Marin… A great piece

I agree with Marin. This would be quite helpful if you annotate a nicely structured literature from previously published research articles.

Awesome article for my research.

I thank you immensely for this wonderful guide

It is indeed thought and supportive work for the futurist researcher and students

Very educative and good time to get guide. Thank you

Great work, very insightful. Thank you.

Thanks for this wonderful presentation. My question is that do I put all the variables into a single conceptual framework or each hypothesis will have it own conceptual framework?

Thank you very much, very helpful

This is very educative and precise . Thank you very much for dropping this kind of write up .

Pheeww, so damn helpful, thank you for this informative piece.

I’m doing a research project topic ; stool analysis for parasitic worm (enteric) worm, how do I structure it, thanks.

comprehensive explanation. Help us by pasting the URL of some good “literature review” for better understanding.

great piece. thanks for the awesome explanation. it is really worth sharing. I have a little question, if anyone can help me out, which of the options in the body of literature can be best fit if you are writing an architectural thesis that deals with design?

I am doing a research on nanofluids how can l structure it?

Beautifully clear.nThank you!

Lucid! Thankyou!

Brilliant work, well understood, many thanks

I like how this was so clear with simple language 😊😊 thank you so much 😊 for these information 😊

Insightful. I was struggling to come up with a sensible literature review but this has been really helpful. Thank you!

You have given thought-provoking information about the review of the literature.

Thank you. It has made my own research better and to impart your work to students I teach

I learnt a lot from this teaching. It’s a great piece.

I am doing research on EFL teacher motivation for his/her job. How Can I structure it? Is there any detailed template, additional to this?

You are so cool! I do not think I’ve read through something like this before. So nice to find somebody with some genuine thoughts on this issue. Seriously.. thank you for starting this up. This site is one thing that is required on the internet, someone with a little originality!

I’m asked to do conceptual, theoretical and empirical literature, and i just don’t know how to structure it

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• Subject Guides

Systematic, Scoping, and Other Literature Reviews: Overview

• Project Planning

What Is a Systematic Review?

Regular literature reviews are simply summaries of the literature on a particular topic. A systematic review, however, is a comprehensive literature review conducted to answer a specific research question. Authors of a systematic review aim to find, code, appraise, and synthesize all of the previous research on their question in an unbiased and well-documented manner. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) outline the minimum amount of information that needs to be reported at the conclusion of a systematic review project. 

Other types of what are known as "evidence syntheses," such as scoping, rapid, and integrative reviews, have varying methodologies. While systematic reviews originated with and continue to be a popular publication type in medicine and other health sciences fields, more and more researchers in other disciplines are choosing to conduct evidence syntheses. 

This guide will walk you through the major steps of a systematic review and point you to key resources including Covidence, a systematic review project management tool. For help with systematic reviews and other major literature review projects, please send us an email at  [email protected] .

Getting Help with Reviews

Organization such as the Institute of Medicine recommend that you consult a librarian when conducting a systematic review. Librarians at the University of Nevada, Reno can help you:

• Understand best practices for conducting systematic reviews and other evidence syntheses in your discipline
• Choose and formulate a research question
• Decide which review type (e.g., systematic, scoping, rapid, etc.) is the best fit for your project
• Determine what to include and where to register a systematic review protocol
• Select search terms and develop a search strategy
• Identify databases and platforms to search
• Find the full text of articles and other sources
• Become familiar with free citation management (e.g., EndNote, Zotero)
• Get access to you and help using Covidence, a systematic review project management tool

Doing a Systematic Review

• Plan - This is the project planning stage. You and your team will need to develop a good research question, determine the type of review you will conduct (systematic, scoping, rapid, etc.), and establish the inclusion and exclusion criteria (e.g., you're only going to look at studies that use a certain methodology). All of this information needs to be included in your protocol. You'll also need to ensure that the project is viable - has someone already done a systematic review on this topic? Do some searches and check the various protocol registries to find out. 
• Identify - Next, a comprehensive search of the literature is undertaken to ensure all studies that meet the predetermined criteria are identified. Each research question is different, so the number and types of databases you'll search - as well as other online publication venues - will vary. Some standards and guidelines specify that certain databases (e.g., MEDLINE, EMBASE) should be searched regardless. Your subject librarian can help you select appropriate databases to search and develop search strings for each of those databases.  
• Evaluate - In this step, retrieved articles are screened and sorted using the predetermined inclusion and exclusion criteria. The risk of bias for each included study is also assessed around this time. It's best if you import search results into a citation management tool (see below) to clean up the citations and remove any duplicates. You can then use a tool like Rayyan (see below) to screen the results. You should begin by screening titles and abstracts only, and then you'll examine the full text of any remaining articles. Each study should be reviewed by a minimum of two people on the project team. 
• Collect - Each included study is coded and the quantitative or qualitative data contained in these studies is then synthesized. You'll have to either find or develop a coding strategy or form that meets your needs. 
• Explain - The synthesized results are articulated and contextualized. What do the results mean? How have they answered your research question?
• Summarize - The final report provides a complete description of the methods and results in a clear, transparent fashion. 

Adapted from

Types of reviews, systematic review.

These types of studies employ a systematic method to analyze and synthesize the results of numerous studies. "Systematic" in this case means following a strict set of steps - as outlined by entities like PRISMA and the Institute of Medicine - so as to make the review more reproducible and less biased. Consistent, thorough documentation is also key. Reviews of this type are not meant to be conducted by an individual but rather a (small) team of researchers. Systematic reviews are widely used in the health sciences, often to find a generalized conclusion from multiple evidence-based studies. 

Meta-Analysis

A systematic method that uses statistics to analyze the data from numerous studies. The researchers combine the data from studies with similar data types and analyze them as a single, expanded dataset. Meta-analyses are a type of systematic review.

Scoping Review

A scoping review employs the systematic review methodology to explore a broader topic or question rather than a specific and answerable one, as is generally the case with a systematic review. Authors of these types of reviews seek to collect and categorize the existing literature so as to identify any gaps.

Rapid Review

Rapid reviews are systematic reviews conducted under a time constraint. Researchers make use of workarounds to complete the review quickly (e.g., only looking at English-language publications), which can lead to a less thorough and more biased review. 

Narrative Review

A traditional literature review that summarizes and synthesizes the findings of numerous original research articles. The purpose and scope of narrative literature reviews vary widely and do not follow a set protocol. Most literature reviews are narrative reviews. 

Umbrella Review

Umbrella reviews are, essentially, systematic reviews of systematic reviews. These compile evidence from multiple review studies into one usable document. 

Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal , vol. 26, no. 2, 2009, pp. 91-108. doi: 10.1111/j.1471-1842.2009.00848.x .

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How To Write A Literature Review - A Complete Guide

Table of Contents

A literature review is much more than just another section in your research paper. It forms the very foundation of your research. It is a formal piece of writing where you analyze the existing theoretical framework, principles, and assumptions and use that as a base to shape your approach to the research question.

Curating and drafting a solid literature review section not only lends more credibility to your research paper but also makes your research tighter and better focused. But, writing literature reviews is a difficult task. It requires extensive reading, plus you have to consider market trends and technological and political changes, which tend to change in the blink of an eye.

Now streamline your literature review process with the help of SciSpace Copilot. With this AI research assistant, you can efficiently synthesize and analyze a vast amount of information, identify key themes and trends, and uncover gaps in the existing research. Get real-time explanations, summaries, and answers to your questions for the paper you're reviewing, making navigating and understanding the complex literature landscape easier.

In this comprehensive guide, we will explore everything from the definition of a literature review, its appropriate length, various types of literature reviews, and how to write one.

What is a literature review?

A literature review is a collation of survey, research, critical evaluation, and assessment of the existing literature in a preferred domain.

Eminent researcher and academic Arlene Fink, in her book Conducting Research Literature Reviews , defines it as the following:

“A literature review surveys books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated.

Literature reviews are designed to provide an overview of sources you have explored while researching a particular topic, and to demonstrate to your readers how your research fits within a larger field of study.”

Simply put, a literature review can be defined as a critical discussion of relevant pre-existing research around your research question and carving out a definitive place for your study in the existing body of knowledge. Literature reviews can be presented in multiple ways: a section of an article, the whole research paper itself, or a chapter of your thesis.

A literature review does function as a summary of sources, but it also allows you to analyze further, interpret, and examine the stated theories, methods, viewpoints, and, of course, the gaps in the existing content.

As an author, you can discuss and interpret the research question and its various aspects and debate your adopted methods to support the claim.

What is the purpose of a literature review?

A literature review is meant to help your readers understand the relevance of your research question and where it fits within the existing body of knowledge. As a researcher, you should use it to set the context, build your argument, and establish the need for your study.

What is the importance of a literature review?

The literature review is a critical part of research papers because it helps you:

• Gain an in-depth understanding of your research question and the surrounding area
• Convey that you have a thorough understanding of your research area and are up-to-date with the latest changes and advancements
• Establish how your research is connected or builds on the existing body of knowledge and how it could contribute to further research
• Elaborate on the validity and suitability of your theoretical framework and research methodology
• Identify and highlight gaps and shortcomings in the existing body of knowledge and how things need to change
• Convey to readers how your study is different or how it contributes to the research area

How long should a literature review be?

Ideally, the literature review should take up 15%-40% of the total length of your manuscript. So, if you have a 10,000-word research paper, the minimum word count could be 1500.

Your literature review format depends heavily on the kind of manuscript you are writing — an entire chapter in case of doctoral theses, a part of the introductory section in a research article, to a full-fledged review article that examines the previously published research on a topic.

Another determining factor is the type of research you are doing. The literature review section tends to be longer for secondary research projects than primary research projects.

What are the different types of literature reviews?

All literature reviews are not the same. There are a variety of possible approaches that you can take. It all depends on the type of research you are pursuing.

Here are the different types of literature reviews:

Argumentative review

It is called an argumentative review when you carefully present literature that only supports or counters a specific argument or premise to establish a viewpoint.

Integrative review

It is a type of literature review focused on building a comprehensive understanding of a topic by combining available theoretical frameworks and empirical evidence.

Methodological review

This approach delves into the ''how'' and the ''what" of the research question —  you cannot look at the outcome in isolation; you should also review the methodology used.

Systematic review

This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research and collect, report, and analyze data from the studies included in the review.

Meta-analysis review

Meta-analysis uses statistical methods to summarize the results of independent studies. By combining information from all relevant studies, meta-analysis can provide more precise estimates of the effects than those derived from the individual studies included within a review.

Historical review

Historical literature reviews focus on examining research throughout a period, often starting with the first time an issue, concept, theory, or phenomenon emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and identify future research's likely directions.

Theoretical Review

This form aims to examine the corpus of theory accumulated regarding an issue, concept, theory, and phenomenon. The theoretical literature review helps to establish what theories exist, the relationships between them, the degree the existing approaches have been investigated, and to develop new hypotheses to be tested.

Scoping Review

The Scoping Review is often used at the beginning of an article, dissertation, or research proposal. It is conducted before the research to highlight gaps in the existing body of knowledge and explains why the project should be greenlit.

State-of-the-Art Review

The State-of-the-Art review is conducted periodically, focusing on the most recent research. It describes what is currently known, understood, or agreed upon regarding the research topic and highlights where there are still disagreements.

Can you use the first person in a literature review?

When writing literature reviews, you should avoid the usage of first-person pronouns. It means that instead of "I argue that" or "we argue that," the appropriate expression would be "this research paper argues that."

Do you need an abstract for a literature review?

Ideally, yes. It is always good to have a condensed summary that is self-contained and independent of the rest of your review. As for how to draft one, you can follow the same fundamental idea when preparing an abstract for a literature review. It should also include:

• The research topic and your motivation behind selecting it
• A one-sentence thesis statement
• An explanation of the kinds of literature featured in the review
• Summary of what you've learned
• Conclusions you drew from the literature you reviewed
• Potential implications and future scope for research

Here's an example of the abstract of a literature review

Is a literature review written in the past tense?

Yes, the literature review should ideally be written in the past tense. You should not use the present or future tense when writing one. The exceptions are when you have statements describing events that happened earlier than the literature you are reviewing or events that are currently occurring; then, you can use the past perfect or present perfect tenses.

How many sources for a literature review?

There are multiple approaches to deciding how many sources to include in a literature review section. The first approach would be to look level you are at as a researcher. For instance, a doctoral thesis might need 60+ sources. In contrast, you might only need to refer to 5-15 sources at the undergraduate level.

The second approach is based on the kind of literature review you are doing — whether it is merely a chapter of your paper or if it is a self-contained paper in itself. When it is just a chapter, sources should equal the total number of pages in your article's body. In the second scenario, you need at least three times as many sources as there are pages in your work.

Quick tips on how to write a literature review

To know how to write a literature review, you must clearly understand its impact and role in establishing your work as substantive research material.

You need to follow the below-mentioned steps, to write a literature review:

• Outline the purpose behind the literature review
• Search relevant literature
• Examine and assess the relevant resources
• Discover connections by drawing deep insights from the resources
• Structure planning to write a good literature review

1. Outline and identify the purpose of  a literature review

As a first step on how to write a literature review, you must know what the research question or topic is and what shape you want your literature review to take. Ensure you understand the research topic inside out, or else seek clarifications. You must be able to the answer below questions before you start:

• How many sources do I need to include?
• What kind of sources should I analyze?
• How much should I critically evaluate each source?
• Should I summarize, synthesize or offer a critique of the sources?
• Do I need to include any background information or definitions?

Additionally, you should know that the narrower your research topic is, the swifter it will be for you to restrict the number of sources to be analyzed.

2. Search relevant literature

Dig deeper into search engines to discover what has already been published around your chosen topic. Make sure you thoroughly go through appropriate reference sources like books, reports, journal articles, government docs, and web-based resources.

You must prepare a list of keywords and their different variations. You can start your search from any library’s catalog, provided you are an active member of that institution. The exact keywords can be extended to widen your research over other databases and academic search engines like:

• Google Scholar
• Microsoft Academic
• Science.gov

Besides, it is not advisable to go through every resource word by word. Alternatively, what you can do is you can start by reading the abstract and then decide whether that source is relevant to your research or not.

Additionally, you must spend surplus time assessing the quality and relevance of resources. It would help if you tried preparing a list of citations to ensure that there lies no repetition of authors, publications, or articles in the literature review.

3. Examine and assess the sources

It is nearly impossible for you to go through every detail in the research article. So rather than trying to fetch every detail, you have to analyze and decide which research sources resemble closest and appear relevant to your chosen domain.

While analyzing the sources, you should look to find out answers to questions like:

• What question or problem has the author been describing and debating?
• What is the definition of critical aspects?
• How well the theories, approach, and methodology have been explained?
• Whether the research theory used some conventional or new innovative approach?
• How relevant are the key findings of the work?
• In what ways does it relate to other sources on the same topic?
• What challenges does this research paper pose to the existing theory
• What are the possible contributions or benefits it adds to the subject domain?

Be always mindful that you refer only to credible and authentic resources. It would be best if you always take references from different publications to validate your theory.

Always keep track of important information or data you can present in your literature review right from the beginning. It will help steer your path from any threats of plagiarism and also make it easier to curate an annotated bibliography or reference section.

4. Discover connections

At this stage, you must start deciding on the argument and structure of your literature review. To accomplish this, you must discover and identify the relations and connections between various resources while drafting your abstract.

A few aspects that you should be aware of while writing a literature review include:

• Rise to prominence: Theories and methods that have gained reputation and supporters over time.
• Constant scrutiny: Concepts or theories that repeatedly went under examination.
• Contradictions and conflicts: Theories, both the supporting and the contradictory ones, for the research topic.
• Knowledge gaps: What exactly does it fail to address, and how to bridge them with further research?
• Influential resources: Significant research projects available that have been upheld as milestones or perhaps, something that can modify the current trends

Once you join the dots between various past research works, it will be easier for you to draw a conclusion and identify your contribution to the existing knowledge base.

5. Structure planning to write a good literature review

There exist different ways towards planning and executing the structure of a literature review. The format of a literature review varies and depends upon the length of the research.

Like any other research paper, the literature review format must contain three sections: introduction, body, and conclusion. The goals and objectives of the research question determine what goes inside these three sections.

Nevertheless, a good literature review can be structured according to the chronological, thematic, methodological, or theoretical framework approach.

Literature review samples

1. Standalone

2. As a section of a research paper

How SciSpace Discover makes literature review a breeze?

SciSpace Discover is a one-stop solution to do an effective literature search and get barrier-free access to scientific knowledge. It is an excellent repository where you can find millions of only peer-reviewed articles and full-text PDF files. Here’s more on how you can use it:

Find the right information

Find what you want quickly and easily with comprehensive search filters that let you narrow down papers according to PDF availability, year of publishing, document type, and affiliated institution. Moreover, you can sort the results based on the publishing date, citation count, and relevance.

Assess credibility of papers quickly

When doing the literature review, it is critical to establish the quality of your sources. They form the foundation of your research. SciSpace Discover helps you assess the quality of a source by providing an overview of its references, citations, and performance metrics.

Get the complete picture in no time

SciSpace Discover’s personalized suggestion engine helps you stay on course and get the complete picture of the topic from one place. Every time you visit an article page, it provides you links to related papers. Besides that, it helps you understand what’s trending, who are the top authors, and who are the leading publishers on a topic.

Make referring sources super easy

To ensure you don't lose track of your sources, you must start noting down your references when doing the literature review. SciSpace Discover makes this step effortless. Click the 'cite' button on an article page, and you will receive preloaded citation text in multiple styles — all you've to do is copy-paste it into your manuscript.

Final tips on how to write a literature review

A massive chunk of time and effort is required to write a good literature review. But, if you go about it systematically, you'll be able to save a ton of time and build a solid foundation for your research.

We hope this guide has helped you answer several key questions you have about writing literature reviews.

Would you like to explore SciSpace Discover and kick off your literature search right away? You can get started here .

Frequently Asked Questions (FAQs)

1. how to start a literature review.

• What questions do you want to answer?

• What sources do you need to answer these questions?

• What information do these sources contain?

• How can you use this information to answer your questions?

2. What to include in a literature review?

• A brief background of the problem or issue

• What has previously been done to address the problem or issue

• A description of what you will do in your project

• How this study will contribute to research on the subject

3. Why literature review is important?

The literature review is an important part of any research project because it allows the writer to look at previous studies on a topic and determine existing gaps in the literature, as well as what has already been done. It will also help them to choose the most appropriate method for their own study.

4. How to cite a literature review in APA format?

To cite a literature review in APA style, you need to provide the author's name, the title of the article, and the year of publication. For example: Patel, A. B., & Stokes, G. S. (2012). The relationship between personality and intelligence: A meta-analysis of longitudinal research. Personality and Individual Differences, 53(1), 16-21

5. What are the components of a literature review?

• A brief introduction to the topic, including its background and context. The introduction should also include a rationale for why the study is being conducted and what it will accomplish.

• A description of the methodologies used in the study. This can include information about data collection methods, sample size, and statistical analyses.

• A presentation of the findings in an organized format that helps readers follow along with the author's conclusions.

6. What are common errors in writing literature review?

• Not spending enough time to critically evaluate the relevance of resources, observations and conclusions.

• Totally relying on secondary data while ignoring primary data.

• Letting your personal bias seep into your interpretation of existing literature.

• No detailed explanation of the procedure to discover and identify an appropriate literature review.

7. What are the 5 C's of writing literature review?

• Cite - the sources you utilized and referenced in your research.

• Compare - existing arguments, hypotheses, methodologies, and conclusions found in the knowledge base.

• Contrast - the arguments, topics, methodologies, approaches, and disputes that may be found in the literature.

• Critique - the literature and describe the ideas and opinions you find more convincing and why.

• Connect - the various studies you reviewed in your research.

8. How many sources should a literature review have?

When it is just a chapter, sources should equal the total number of pages in your article's body. if it is a self-contained paper in itself, you need at least three times as many sources as there are pages in your work.

9. Can literature review have diagrams?

• To represent an abstract idea or concept

• To explain the steps of a process or procedure

• To help readers understand the relationships between different concepts

10. How old should sources be in a literature review?

Sources for a literature review should be as current as possible or not older than ten years. The only exception to this rule is if you are reviewing a historical topic and need to use older sources.

11. What are the types of literature review?

• Argumentative review

• Integrative review

• Methodological review

• Systematic review

• Meta-analysis review

• Historical review

• Theoretical review

• Scoping review

• State-of-the-Art review

12. Is a literature review mandatory?

Yes. Literature review is a mandatory part of any research project. It is a critical step in the process that allows you to establish the scope of your research, and provide a background for the rest of your work.

But before you go,

• Six Online Tools for Easy Literature Review
• Evaluating literature review: systematic vs. scoping reviews
• Systematic Approaches to a Successful Literature Review
• Writing Integrative Literature Reviews: Guidelines and Examples

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What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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What is a Literature Review?

A literature or narrative review is a comprehensive review and analysis of the published literature on a specific topic or research question. The literature that is reviewed contains: books, articles, academic articles, conference proceedings, association papers, and dissertations. It contains the most pertinent studies and points to important past and current research and practices. It provides background and context, and shows how your research will contribute to the field. 

A literature review should: 

• Provide a comprehensive and updated review of the literature;
• Explain why this review has taken place;
• Articulate a position or hypothesis;
• Acknowledge and account for conflicting and corroborating points of view

From  S age Research Methods

Purpose of a Literature Review

A literature review can be written as an introduction to a study to:

• Demonstrate how a study fills a gap in research
• Compare a study with other research that's been done

Or it can be a separate work (a research article on its own) which:

• Organizes or describes a topic
• Describes variables within a particular issue/problem

Limitations of a Literature Review

Some of the limitations of a literature review are:

• It's a snapshot in time. Unlike other reviews, this one has beginning, a middle and an end. There may be future developments that could make your work less relevant.
• It may be too focused. Some niche studies may miss the bigger picture.
• It can be difficult to be comprehensive. There is no way to make sure all the literature on a topic was considered.
• It is easy to be biased if you stick to top tier journals. There may be other places where people are publishing exemplary research. Look to open access publications and conferences to reflect a more inclusive collection. Also, make sure to include opposing views (and not just supporting evidence).

Source: Grant, Maria J., and Andrew Booth. “A Typology of Reviews: An Analysis of 14 Review Types and Associated Methodologies.” Health Information & Libraries Journal, vol. 26, no. 2, June 2009, pp. 91–108. Wiley Online Library, doi:10.1111/j.1471-1842.2009.00848.x.

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For help in other subject areas, please see the guide to library specialists by subject .

Periodically, UT Libraries runs a workshop covering the basics and library support for literature reviews. While we try to offer these once per academic year, we find providing the recording to be helpful to community members who have missed the session. Following is the most recent recording of the workshop, Conducting a Literature Review. To view the recording, a UT login is required.

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A literature review surveys prior research published in books, scholarly articles, and any other sources relevant to a particular issue, area of research, or theory, and by so doing, provides a description, summary, and critical evaluation of these works in relation to the research problem being investigated. Literature reviews are designed to provide an overview of sources you have used in researching a particular topic and to demonstrate to your readers how your research fits within existing scholarship about the topic.

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . Fourth edition. Thousand Oaks, CA: SAGE, 2014.

Importance of a Good Literature Review

A literature review may consist of simply a summary of key sources, but in the social sciences, a literature review usually has an organizational pattern and combines both summary and synthesis, often within specific conceptual categories . A summary is a recap of the important information of the source, but a synthesis is a re-organization, or a reshuffling, of that information in a way that informs how you are planning to investigate a research problem. The analytical features of a literature review might:

• Give a new interpretation of old material or combine new with old interpretations,
• Trace the intellectual progression of the field, including major debates,
• Depending on the situation, evaluate the sources and advise the reader on the most pertinent or relevant research, or
• Usually in the conclusion of a literature review, identify where gaps exist in how a problem has been researched to date.

Given this, the purpose of a literature review is to:

• Place each work in the context of its contribution to understanding the research problem being studied.
• Describe the relationship of each work to the others under consideration.
• Identify new ways to interpret prior research.
• Reveal any gaps that exist in the literature.
• Resolve conflicts amongst seemingly contradictory previous studies.
• Identify areas of prior scholarship to prevent duplication of effort.
• Point the way in fulfilling a need for additional research.
• Locate your own research within the context of existing literature [very important].

Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper. 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . Los Angeles, CA: SAGE, 2011; Knopf, Jeffrey W. "Doing a Literature Review." PS: Political Science and Politics 39 (January 2006): 127-132; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012.

Types of Literature Reviews

It is important to think of knowledge in a given field as consisting of three layers. First, there are the primary studies that researchers conduct and publish. Second are the reviews of those studies that summarize and offer new interpretations built from and often extending beyond the primary studies. Third, there are the perceptions, conclusions, opinion, and interpretations that are shared informally among scholars that become part of the body of epistemological traditions within the field.

In composing a literature review, it is important to note that it is often this third layer of knowledge that is cited as "true" even though it often has only a loose relationship to the primary studies and secondary literature reviews. Given this, while literature reviews are designed to provide an overview and synthesis of pertinent sources you have explored, there are a number of approaches you could adopt depending upon the type of analysis underpinning your study.

Argumentative Review This form examines literature selectively in order to support or refute an argument, deeply embedded assumption, or philosophical problem already established in the literature. The purpose is to develop a body of literature that establishes a contrarian viewpoint. Given the value-laden nature of some social science research [e.g., educational reform; immigration control], argumentative approaches to analyzing the literature can be a legitimate and important form of discourse. However, note that they can also introduce problems of bias when they are used to make summary claims of the sort found in systematic reviews [see below].

Integrative Review Considered a form of research that reviews, critiques, and synthesizes representative literature on a topic in an integrated way such that new frameworks and perspectives on the topic are generated. The body of literature includes all studies that address related or identical hypotheses or research problems. A well-done integrative review meets the same standards as primary research in regard to clarity, rigor, and replication. This is the most common form of review in the social sciences.

Historical Review Few things rest in isolation from historical precedent. Historical literature reviews focus on examining research throughout a period of time, often starting with the first time an issue, concept, theory, phenomena emerged in the literature, then tracing its evolution within the scholarship of a discipline. The purpose is to place research in a historical context to show familiarity with state-of-the-art developments and to identify the likely directions for future research.

Methodological Review A review does not always focus on what someone said [findings], but how they came about saying what they say [method of analysis]. Reviewing methods of analysis provides a framework of understanding at different levels [i.e. those of theory, substantive fields, research approaches, and data collection and analysis techniques], how researchers draw upon a wide variety of knowledge ranging from the conceptual level to practical documents for use in fieldwork in the areas of ontological and epistemological consideration, quantitative and qualitative integration, sampling, interviewing, data collection, and data analysis. This approach helps highlight ethical issues which you should be aware of and consider as you go through your own study.

Systematic Review This form consists of an overview of existing evidence pertinent to a clearly formulated research question, which uses pre-specified and standardized methods to identify and critically appraise relevant research, and to collect, report, and analyze data from the studies that are included in the review. The goal is to deliberately document, critically evaluate, and summarize scientifically all of the research about a clearly defined research problem . Typically it focuses on a very specific empirical question, often posed in a cause-and-effect form, such as "To what extent does A contribute to B?" This type of literature review is primarily applied to examining prior research studies in clinical medicine and allied health fields, but it is increasingly being used in the social sciences.

Theoretical Review The purpose of this form is to examine the corpus of theory that has accumulated in regard to an issue, concept, theory, phenomena. The theoretical literature review helps to establish what theories already exist, the relationships between them, to what degree the existing theories have been investigated, and to develop new hypotheses to be tested. Often this form is used to help establish a lack of appropriate theories or reveal that current theories are inadequate for explaining new or emerging research problems. The unit of analysis can focus on a theoretical concept or a whole theory or framework.

NOTE : Most often the literature review will incorporate some combination of types. For example, a review that examines literature supporting or refuting an argument, assumption, or philosophical problem related to the research problem will also need to include writing supported by sources that establish the history of these arguments in the literature.

Baumeister, Roy F. and Mark R. Leary. "Writing Narrative Literature Reviews."  Review of General Psychology 1 (September 1997): 311-320; Mark R. Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Kennedy, Mary M. "Defining a Literature." Educational Researcher 36 (April 2007): 139-147; Petticrew, Mark and Helen Roberts. Systematic Reviews in the Social Sciences: A Practical Guide . Malden, MA: Blackwell Publishers, 2006; Torracro, Richard. "Writing Integrative Literature Reviews: Guidelines and Examples." Human Resource Development Review 4 (September 2005): 356-367; Rocco, Tonette S. and Maria S. Plakhotnik. "Literature Reviews, Conceptual Frameworks, and Theoretical Frameworks: Terms, Functions, and Distinctions." Human Ressource Development Review 8 (March 2008): 120-130; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

Structure and Writing Style

I.  Thinking About Your Literature Review

The structure of a literature review should include the following in support of understanding the research problem :

• An overview of the subject, issue, or theory under consideration, along with the objectives of the literature review,
• Division of works under review into themes or categories [e.g. works that support a particular position, those against, and those offering alternative approaches entirely],
• An explanation of how each work is similar to and how it varies from the others,
• Conclusions as to which pieces are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research.

The critical evaluation of each work should consider :

• Provenance -- what are the author's credentials? Are the author's arguments supported by evidence [e.g. primary historical material, case studies, narratives, statistics, recent scientific findings]?
• Methodology -- were the techniques used to identify, gather, and analyze the data appropriate to addressing the research problem? Was the sample size appropriate? Were the results effectively interpreted and reported?
• Objectivity -- is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
• Persuasiveness -- which of the author's theses are most convincing or least convincing?
• Validity -- are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

II.  Development of the Literature Review

Four Basic Stages of Writing 1.  Problem formulation -- which topic or field is being examined and what are its component issues? 2.  Literature search -- finding materials relevant to the subject being explored. 3.  Data evaluation -- determining which literature makes a significant contribution to the understanding of the topic. 4.  Analysis and interpretation -- discussing the findings and conclusions of pertinent literature.

Consider the following issues before writing the literature review: Clarify If your assignment is not specific about what form your literature review should take, seek clarification from your professor by asking these questions: 1.  Roughly how many sources would be appropriate to include? 2.  What types of sources should I review (books, journal articles, websites; scholarly versus popular sources)? 3.  Should I summarize, synthesize, or critique sources by discussing a common theme or issue? 4.  Should I evaluate the sources in any way beyond evaluating how they relate to understanding the research problem? 5.  Should I provide subheadings and other background information, such as definitions and/or a history? Find Models Use the exercise of reviewing the literature to examine how authors in your discipline or area of interest have composed their literature review sections. Read them to get a sense of the types of themes you might want to look for in your own research or to identify ways to organize your final review. The bibliography or reference section of sources you've already read, such as required readings in the course syllabus, are also excellent entry points into your own research. Narrow the Topic The narrower your topic, the easier it will be to limit the number of sources you need to read in order to obtain a good survey of relevant resources. Your professor will probably not expect you to read everything that's available about the topic, but you'll make the act of reviewing easier if you first limit scope of the research problem. A good strategy is to begin by searching the USC Libraries Catalog for recent books about the topic and review the table of contents for chapters that focuses on specific issues. You can also review the indexes of books to find references to specific issues that can serve as the focus of your research. For example, a book surveying the history of the Israeli-Palestinian conflict may include a chapter on the role Egypt has played in mediating the conflict, or look in the index for the pages where Egypt is mentioned in the text. Consider Whether Your Sources are Current Some disciplines require that you use information that is as current as possible. This is particularly true in disciplines in medicine and the sciences where research conducted becomes obsolete very quickly as new discoveries are made. However, when writing a review in the social sciences, a survey of the history of the literature may be required. In other words, a complete understanding the research problem requires you to deliberately examine how knowledge and perspectives have changed over time. Sort through other current bibliographies or literature reviews in the field to get a sense of what your discipline expects. You can also use this method to explore what is considered by scholars to be a "hot topic" and what is not.

III.  Ways to Organize Your Literature Review

Chronology of Events If your review follows the chronological method, you could write about the materials according to when they were published. This approach should only be followed if a clear path of research building on previous research can be identified and that these trends follow a clear chronological order of development. For example, a literature review that focuses on continuing research about the emergence of German economic power after the fall of the Soviet Union. By Publication Order your sources by publication chronology, then, only if the order demonstrates a more important trend. For instance, you could order a review of literature on environmental studies of brown fields if the progression revealed, for example, a change in the soil collection practices of the researchers who wrote and/or conducted the studies. Thematic [“conceptual categories”] A thematic literature review is the most common approach to summarizing prior research in the social and behavioral sciences. Thematic reviews are organized around a topic or issue, rather than the progression of time, although the progression of time may still be incorporated into a thematic review. For example, a review of the Internet’s impact on American presidential politics could focus on the development of online political satire. While the study focuses on one topic, the Internet’s impact on American presidential politics, it would still be organized chronologically reflecting technological developments in media. The difference in this example between a "chronological" and a "thematic" approach is what is emphasized the most: themes related to the role of the Internet in presidential politics. Note that more authentic thematic reviews tend to break away from chronological order. A review organized in this manner would shift between time periods within each section according to the point being made. Methodological A methodological approach focuses on the methods utilized by the researcher. For the Internet in American presidential politics project, one methodological approach would be to look at cultural differences between the portrayal of American presidents on American, British, and French websites. Or the review might focus on the fundraising impact of the Internet on a particular political party. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed.

Other Sections of Your Literature Review Once you've decided on the organizational method for your literature review, the sections you need to include in the paper should be easy to figure out because they arise from your organizational strategy. In other words, a chronological review would have subsections for each vital time period; a thematic review would have subtopics based upon factors that relate to the theme or issue. However, sometimes you may need to add additional sections that are necessary for your study, but do not fit in the organizational strategy of the body. What other sections you include in the body is up to you. However, only include what is necessary for the reader to locate your study within the larger scholarship about the research problem.

Here are examples of other sections, usually in the form of a single paragraph, you may need to include depending on the type of review you write:

• Current Situation : Information necessary to understand the current topic or focus of the literature review.
• Sources Used : Describes the methods and resources [e.g., databases] you used to identify the literature you reviewed.
• History : The chronological progression of the field, the research literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
• Selection Methods : Criteria you used to select (and perhaps exclude) sources in your literature review. For instance, you might explain that your review includes only peer-reviewed [i.e., scholarly] sources.
• Standards : Description of the way in which you present your information.
• Questions for Further Research : What questions about the field has the review sparked? How will you further your research as a result of the review?

IV.  Writing Your Literature Review

Once you've settled on how to organize your literature review, you're ready to write each section. When writing your review, keep in mind these issues.

Use Evidence A literature review section is, in this sense, just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence [citations] that demonstrates that what you are saying is valid. Be Selective Select only the most important points in each source to highlight in the review. The type of information you choose to mention should relate directly to the research problem, whether it is thematic, methodological, or chronological. Related items that provide additional information, but that are not key to understanding the research problem, can be included in a list of further readings . Use Quotes Sparingly Some short quotes are appropriate if you want to emphasize a point, or if what an author stated cannot be easily paraphrased. Sometimes you may need to quote certain terminology that was coined by the author, is not common knowledge, or taken directly from the study. Do not use extensive quotes as a substitute for using your own words in reviewing the literature. Summarize and Synthesize Remember to summarize and synthesize your sources within each thematic paragraph as well as throughout the review. Recapitulate important features of a research study, but then synthesize it by rephrasing the study's significance and relating it to your own work and the work of others. Keep Your Own Voice While the literature review presents others' ideas, your voice [the writer's] should remain front and center. For example, weave references to other sources into what you are writing but maintain your own voice by starting and ending the paragraph with your own ideas and wording. Use Caution When Paraphrasing When paraphrasing a source that is not your own, be sure to represent the author's information or opinions accurately and in your own words. Even when paraphrasing an author’s work, you still must provide a citation to that work.

V.  Common Mistakes to Avoid

These are the most common mistakes made in reviewing social science research literature.

• Sources in your literature review do not clearly relate to the research problem;
• You do not take sufficient time to define and identify the most relevant sources to use in the literature review related to the research problem;
• Relies exclusively on secondary analytical sources rather than including relevant primary research studies or data;
• Uncritically accepts another researcher's findings and interpretations as valid, rather than examining critically all aspects of the research design and analysis;
• Does not describe the search procedures that were used in identifying the literature to review;
• Reports isolated statistical results rather than synthesizing them in chi-squared or meta-analytic methods; and,
• Only includes research that validates assumptions and does not consider contrary findings and alternative interpretations found in the literature.

Cook, Kathleen E. and Elise Murowchick. “Do Literature Review Skills Transfer from One Course to Another?” Psychology Learning and Teaching 13 (March 2014): 3-11; Fink, Arlene. Conducting Research Literature Reviews: From the Internet to Paper . 2nd ed. Thousand Oaks, CA: Sage, 2005; Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1998; Jesson, Jill. Doing Your Literature Review: Traditional and Systematic Techniques . London: SAGE, 2011; Literature Review Handout. Online Writing Center. Liberty University; Literature Reviews. The Writing Center. University of North Carolina; Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: SAGE, 2016; Ridley, Diana. The Literature Review: A Step-by-Step Guide for Students . 2nd ed. Los Angeles, CA: SAGE, 2012; Randolph, Justus J. “A Guide to Writing the Dissertation Literature Review." Practical Assessment, Research, and Evaluation. vol. 14, June 2009; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016; Taylor, Dena. The Literature Review: A Few Tips On Conducting It. University College Writing Centre. University of Toronto; Writing a Literature Review. Academic Skills Centre. University of Canberra.

Writing Tip

Break Out of Your Disciplinary Box!

Thinking interdisciplinarily about a research problem can be a rewarding exercise in applying new ideas, theories, or concepts to an old problem. For example, what might cultural anthropologists say about the continuing conflict in the Middle East? In what ways might geographers view the need for better distribution of social service agencies in large cities than how social workers might study the issue? You don’t want to substitute a thorough review of core research literature in your discipline for studies conducted in other fields of study. However, particularly in the social sciences, thinking about research problems from multiple vectors is a key strategy for finding new solutions to a problem or gaining a new perspective. Consult with a librarian about identifying research databases in other disciplines; almost every field of study has at least one comprehensive database devoted to indexing its research literature.

Frodeman, Robert. The Oxford Handbook of Interdisciplinarity . New York: Oxford University Press, 2010.

Another Writing Tip

Don't Just Review for Content!

While conducting a review of the literature, maximize the time you devote to writing this part of your paper by thinking broadly about what you should be looking for and evaluating. Review not just what scholars are saying, but how are they saying it. Some questions to ask:

• How are they organizing their ideas?
• What methods have they used to study the problem?
• What theories have been used to explain, predict, or understand their research problem?
• What sources have they cited to support their conclusions?
• How have they used non-textual elements [e.g., charts, graphs, figures, etc.] to illustrate key points?

When you begin to write your literature review section, you'll be glad you dug deeper into how the research was designed and constructed because it establishes a means for developing more substantial analysis and interpretation of the research problem.

Hart, Chris. Doing a Literature Review: Releasing the Social Science Research Imagination . Thousand Oaks, CA: Sage Publications, 1 998.

Yet Another Writing Tip

When Do I Know I Can Stop Looking and Move On?

Here are several strategies you can utilize to assess whether you've thoroughly reviewed the literature:

• Look for repeating patterns in the research findings . If the same thing is being said, just by different people, then this likely demonstrates that the research problem has hit a conceptual dead end. At this point consider: Does your study extend current research?  Does it forge a new path? Or, does is merely add more of the same thing being said?
• Look at sources the authors cite to in their work . If you begin to see the same researchers cited again and again, then this is often an indication that no new ideas have been generated to address the research problem.
• Search Google Scholar to identify who has subsequently cited leading scholars already identified in your literature review [see next sub-tab]. This is called citation tracking and there are a number of sources that can help you identify who has cited whom, particularly scholars from outside of your discipline. Here again, if the same authors are being cited again and again, this may indicate no new literature has been written on the topic.

Onwuegbuzie, Anthony J. and Rebecca Frels. Seven Steps to a Comprehensive Literature Review: A Multimodal and Cultural Approach . Los Angeles, CA: Sage, 2016; Sutton, Anthea. Systematic Approaches to a Successful Literature Review . Los Angeles, CA: Sage Publications, 2016.

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Writing a Literature Review

• Getting Started

Defining the topic

Limiting the scope.

• Finding the Literature
• Developing a Search Strategy
• Managing Your Research
• Writing the Review
• Systematic Reviews and Other Review Types
• Useful Books
• Useful Videos
• Useful Links
• Commonly Used Terms

Identifying a well-defined research question is the first step for writing a literature review. It should focus on something from the research field that needs to be explored, where there are gaps in the information. This will ensure that your contribution is valuable and that you are providing readers with a different angle or perspective on an issue or problem.

Your topic needs to be given careful consideration. A research question like “why are social networking sites harmful?” is too broad; there will be too much information to write a concise literature review. Change it to “how are online users experiencing or addressing privacy issues on Twitter and Facebook?" and it is more specific. It gives you a niche within the research field to focus on and explore.

Sometimes a broad topic can be narrowed by using one or more extra criteria, which can include:

• population group
• culture/ethnicity
• theoretical framework
• methodology (e.g., qualitative or quantitative, fieldwork/ethnography)

How you narrow the scope can be done in two broad ways, detailed in Developing a Search Strategy :

• add more search strands using AND to give fewer results (see Combining your terms: search operators )
• use "filters" in a database to eliminate results from outside those limits (see Using methodological search filters )
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• Last Updated: Oct 10, 2023 1:52 PM
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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 
• How to write a good literature review 
• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

• Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 
• Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 
• Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 
• Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 
• Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 
• Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

How to write a good literature review

Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. 

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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• Library Guides
• Literature Reviews
• Writing the Review

Literature Reviews: Writing the Review

Outline of review sections.

Your Literature Review should not be a summary and evaluation of each article, one after the other. Your sources should be integrated together to create a narrative on your topic.

Consider the following ways to organize your review:

• By themes, variables, or issues
• By varying perspectives regarding a topic of controversy
• Chronologically, to show how the topic and research have developed over time

Use an outline to organize your sources and ideas in a logical sequence. Identify main points and subpoints, and consider the flow of your review. Outlines can be revised as your ideas develop. They help guide your readers through your ideas and show the hierarchy of your thoughts. What do your readers need to understand first? Where might certain studies fit most naturally? These are the kinds of questions that an outline can clarify.

An example outline for a Literature Review might look like this:

Introduction

• Background information on the topic & definitions
• Purpose of the literature review
• Scope and limitations of the review (what is included /excluded)
• Historical background 
• Overview of the existing research on the topic
• Principle question being asked
• Organization of the literature into categories or themes
• Evaluation of the strengths and weaknesses of each study
• Combining the findings from multiple sources to identify patterns and trends
• Insight into the relationship between your central topic and a larger area of study
• Development of a new research question or hypothesis
• Summary of the key points and findings in the literature
• Discussion of gaps in the existing knowledge
• Implications for future research

Strategies for Writing

Annotated bibliography.

An annotated bibliography collects short descriptions of each source in one place. After you have read each source carefully, set aside some time to write a brief summary. Your summary might be simply informative (e.g. identify the main argument/hypothesis, methods, major findings, and/or conclusions), or it might be evaluative (e.g. state why the source is interesting or useful for your review, or why it is not).

This method is more narrative than the Literature Matrix talked about on the Documenting Your Search page.

Taking the time to write short informative and/or evaluative summaries of your sources while you are researching can help you transition into the drafting stage later on. By making a record of your sources’ contents and your reactions to them, you make it less likely that you will need to go back and re-read many sources while drafting, and you might also start to gain a clearer idea of the overarching shape of your review.

READ EXTANT LIT REVIEWS CLOSELY

As you conduct your research, you will likely read many sources that model the same kind of literature review that you are researching and writing. While your original intent in reading those sources is likely to learn from the studies’ content (e.g. their results and discussion), it will benefit you to re-read these articles rhetorically.

Reading rhetorically means paying attention to how a text is written—how it has been structured, how it presents its claims and analyses, how it employs transitional words and phrases to move from one idea to the next. You might also pay attention to an author’s stylistic choices, like the use of first-person pronouns, active and passive voice, or technical terminology.

See  Finding Example Literature Reviews on the Developing a Research Question page for tips on finding reviews relevant to your topic.

MIND-MAPPING

Creating a mind-map is a form of brainstorming that lets you visualize how your ideas function and relate. Draw the diagram freehand or download software that lets you easily manipulate and group text, images, and shapes ( Coggle ,  FreeMind , MindMaple ).

Write down a central idea, then identify associated concepts, features, or questions around that idea. Make lines attaching various ideas, or arrows to signify directional relationships. Use different shapes, sizes, or colors to indicate commonalities, sequences, or relative importance.

This drafting technique allows you to generate ideas while thinking visually about how they function together. As you follow lines of thought, you can see which ideas can be connected, where certain pathways lead, and what the scope of your project might be. By drawing out a mind-map you may be able to see what elements of your review are underdeveloped and will benefit from more focused attention.

USE VISUALIZATION TOOLS

Attribution.

Thanks to Librarian Jamie Niehof at the University of Michigan for providing permission to reuse and remix this Literature Reviews guide.

Avoiding Bias

Reporting bias.

This occurs when you are summarizing the literature in an unbalanced, inconsistent or distorted way . 

Ways to avoid:

• look for literature that supports multiple perspectives, viewpoints or theories 
• ask multiple people to review your writing for bias
• Last Updated: Apr 9, 2024 3:50 PM
• URL: https://info.library.okstate.edu/literaturereviews

The Literature Review: 5. Organizing the Literature Review

• 1. Introduction
• 2. Why Do a Literature Review?
• 3. Methods for Searching the Literature
• 4. Analysing the Literature
• 5. Organizing the Literature Review
• 6. Writing the Review

1. Organizing Principles

A literature review is a piece of discursive prose, not a list describing or summarizing one piece of literature after another. It should have a single organizing principle:

• Thematic - organize around a topic or issue
• Chronological - sections for each vital time period
• Methodological - focus on the methods used by the researchers/writers

4. Selected Online Resources

• Literature Review in Education & Behavioral Sciences This is an interactive tutorial from Adelphi University Libraries on how to conduct a literature review in education and the behavioural sciences using library databases
• Writing Literature Reviews This tutorial is from the Writing section of Monash University's Language and Learning Online site
• The Literature Review: A Few Tips on Conducting It This guide is from the Health Services Writing Centre at the University of Toronto
• Learn How to Write a Review of the Literature This guide is part of the Writer's Handbook provided by the Writing Center at the University of Wisconsin-Madison

2. Structure of the Literature Review

Although your literature review will rely heavily on the sources you read for its information, you should dictate the structure of the review. It is important that the concepts are presented in an order that makes sense of the context of your research project.

There may be clear divisions on the sets of ideas you want to discuss, in which case your structure may be fairly clear. This is an ideal situation. In most cases, there will be several different possible structures for your review.

Similarly to the structure of the research report itself, the literature review consists of:

• Introduction

Introduction - profile of the study

• Define or identify the general topic to provide the context for reviewing the literature
• Outline why the topic is important
• Identify overall trends in what has been published about the topic
• Identify conflicts in theory, methodology, evidence, and conclusions
• Identify gaps in research and scholarlship
• Explain the criteria to be used in analysing and comparing the literature
• Describe the organization of the review (the sequence)
• If necessary, state why certain literature is or is not included (scope)

Body - summative, comparative, and evaluative discussion of literature reviewed

For a thematic review:

• organize the review into paragraphs that present themes and identify trends relevant to your topic
• each paragraph should deal with a different theme - you need to synthesize several of your readings into each paragraph in such a way that there is a clear connection between the sources
• don't try to list all the materials you have identified in your literature search

From each of the section summaries:

• summarize the main agreements and disagreements in the literature
• summarize the general conclusions that have been drawn
• establish where your own research fits in the context of the existing literature

5. A Final Checklist

• Have you indicated the purpose of the review?
• Have you emphasized recent developments?
• Is there a logic to the way you organized the material?
• Does the amount of detail included on an issue relate to its importance?
• Have you been sufficiently critical of design and methodological issues?
• Have you indicated when results were conflicting or inconclusive and discussed possible reasons?
• Has your summary of the current literature contributed to the reader's understanding of the problems?

3. Tips on Structure

A common error in literature reviews is for writers to present material from one author, followed by information from another, then another.... The way in which you group authors and link ideas will help avoid this problem. To group authors who draw similar conclusions, you can use linking words such as:

• additionally

When authors disagree, linking words that indicate contrast will show how you have analysed their work. Words such as:

• on the other hand
• nonetheless

will indicate to your reader how you have analysed the material. At other times, you may want to qualify an author's work (using such words as specifically, usually, or generally ) or use an example ( thus, namely, to illustrate ). In this way you ensure that you are synthesizing the material, not just describing the work already carried out in your field.

Another major problem is that literature reviews are often written as if they stand alone, without links to the rest of the paper. There needs to be a clear relationship between the literature review and the methodology to follow.

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• Next: 6. Writing the Review >>
• Last Updated: Feb 8, 2022 5:25 PM
• URL: https://libguides.uwi.edu/litreviewsoe

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Cochrane Training

Chapter 2: determining the scope of the review and the questions it will address.

James Thomas, Dylan Kneale, Joanne E McKenzie, Sue E Brennan, Soumyadeep Bhaumik

Key Points:

• Systematic reviews should address answerable questions and fill important gaps in knowledge.
• Developing good review questions takes time, expertise and engagement with intended users of the review.
• Cochrane Reviews can focus on broad questions, or be more narrowly defined. There are advantages and disadvantages of each.
• Logic models are a way of documenting how interventions, particularly complex interventions, are intended to ‘work’, and can be used to refine review questions and the broader scope of the review.
• Using priority-setting exercises, involving relevant stakeholders, and ensuring that the review takes account of issues relating to equity can be strategies for ensuring that the scope and focus of reviews address the right questions.

Cite this chapter as: Thomas J, Kneale D, McKenzie JE, Brennan SE, Bhaumik S. Chapter 2: Determining the scope of the review and the questions it will address. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.4 (updated August 2023). Cochrane, 2023. Available from www.training.cochrane.org/handbook .

2.1 Rationale for well-formulated questions

As with any research, the first and most important decision in preparing a systematic review is to determine its focus. This is best done by clearly framing the questions the review seeks to answer. The focus of any Cochrane Review should be on questions that are important to people making decisions about health or health care. These decisions will usually need to take into account both the benefits and harms of interventions (see MECIR Box 2.1.a ). Good review questions often take time to develop, requiring engagement with not only the subject area, but with a wide group of stakeholders (Section 2.4.2 ).

Well-formulated questions will guide many aspects of the review process, including determining eligibility criteria, searching for studies, collecting data from included studies, structuring the syntheses and presenting findings (Cooper 1984, Hedges 1994, Oliver et al 2017) . In Cochrane Reviews, questions are stated broadly as review ‘Objectives’, and operationalized in terms of the studies that will be eligible to answer those questions as ‘Criteria for considering studies for this review’. As well as focusing review conduct, the contents of these sections are used by readers in their initial assessments of whether the review is likely to be directly relevant to the issues they face.

The FINER criteria have been proposed as encapsulating the issues that should be addressed when developing research questions. These state that questions should be F easible, I nteresting, N ovel, E thical, and R elevant (Cummings et al 2007). All of these criteria raise important issues for consideration at the outset of a review and should be borne in mind when questions are formulated.

A feasible review is one that asks a question that the author team is capable of addressing using the evidence available. Issues concerning the breadth of a review are discussed in Section 2.3.1 , but in terms of feasibility it is important not to ask a question that will result in retrieving unmanageable quantities of information; up-front scoping work will help authors to define sensible boundaries for their reviews. Likewise, while it can be useful to identify gaps in the evidence base, review authors and stakeholders should be aware of the possibility of asking a question that may not be answerable using the existing evidence (i.e. that will result in an ‘empty’ review, see also Section 2.5.3 ).

Embarking on a review that authors are interested in is important because reviews are a significant undertaking and review authors need sufficient commitment to see the work through to its conclusion.

A novel review will address a genuine gap in knowledge, so review authors should be aware of any related or overlapping reviews. This reduces duplication of effort, and also ensures that authors understand the wider research context to which their review will contribute. Authors should check for pre-existing syntheses in the published research literature and also for ongoing reviews in the PROSPERO register of systematic reviews before beginning their own review.

Given the opportunity cost involved in undertaking an activity as demanding as a systematic review, authors should ensure that their work is relevant by: (i) involving relevant stakeholders in defining its focus and the questions it will address; and (ii) writing up the review in such a way as to facilitate the translation of its findings to inform decisions. The GRADE framework aims to achieve this, and should be considered throughout the review process, not only when it is being written up (see Chapter 14 and Chapter 15 ).

Consideration of opportunity costs is also relevant in terms of the ethics of conducting a review, though ethical issues should also be considered primarily in terms of the questions that are prioritized for answering and the way that they are framed. Research questions are often not value-neutral, and the way that a given problem is approached can have political implications which can result in, for example, the widening of health inequalities (whether intentional or not). These issues are explored in Section 2.4.3 and Chapter 16 .

MECIR Box 2.1.a Relevant expectations for conduct of intervention reviews

2.2 Aims of reviews of interventions

Systematic reviews can address any question that can be answered by a primary research study. This Handbook focuses on a subset of all possible review questions: the impact of intervention(s) implemented within a specified human population. Even within these limits, systematic reviews examining the effects of intervention(s) can vary quite markedly in their aims. Some will focus specifically on evidence of an effect of an intervention compared with a specific alternative, whereas others may examine a range of different interventions. Reviews that examine multiple interventions and aim to identify which might be the most effective can be broader and more challenging than those looking at single interventions. These can also be the most useful for end users, where decision making involves selecting from a number of intervention options. The incorporation of network meta-analysis as a core method in this edition of the Handbook (see Chapter 11 ) reflects the growing importance of these types of reviews.

As well as looking at the balance of benefit and harm that can be attributed to a given intervention, reviews within the ambit of this Handbook might also aim to investigate the relationship between the size of an intervention effect and other characteristics, such as aspects of the population, the intervention itself, how the outcome is measured, or the methodology of the primary research studies included. Such approaches might be used to investigate which components of multi-component interventions are more or less important or essential (and when). While it is not always necessary to know how an intervention achieves its effect for it to be useful, many reviews will aim to articulate an intervention’s mechanisms of action (see Section 2.5.1 ), either by making this an explicit aim of the review itself (see Chapter 17 and Chapter 21 ), or when describing the scope of the review. Understanding how an intervention works (or is intended to work) can be an important aid to decision makers in assessing the applicability of the review to their situation. These investigations can be assisted by the incorporation of results from process evaluations conducted alongside trials (see Chapter 21 ). Further, many decisions in policy and practice are at least partially constrained by the resource available, so review authors often need to consider the economic context of interventions (see Chapter 20 ).

2.3 Defining the scope of a review question

Studies comparing healthcare interventions, notably randomized trials, use the outcomes of participants to compare the effects of different interventions. Statistical syntheses (e.g. meta-analysis) focus on comparisons of interventions, such as a new intervention versus a control intervention (which may represent conditions of usual practice or care), or the comparison of two competing interventions. Throughout the Handbook we use the terminology experimental intervention versus comparator intervention. This implies a need to identify one of the interventions as experimental, and is used only for convenience since all methods apply to both controlled and head-to-head comparisons. The contrast between the outcomes of two groups treated differently is known as the ‘effect’, the ‘treatment effect’ or the ‘intervention effect’; we generally use the last of these throughout the Handbook .

A statement of the review’s objectives should begin with a precise statement of the primary objective, ideally in a single sentence ( MECIR Box 2.3.a ). Where possible the style should be of the form ‘To assess the effects of [ intervention or comparison ] for [ health problem ] in [ types of people, disease or problem and setting if specified ]’. This might be followed by one or more secondary objectives, for example relating to different participant groups, different comparisons of interventions or different outcome measures. The detailed specification of the review question(s) requires consideration of several key components (Richardson et al 1995, Counsell 1997) which can often be encapsulated by the ‘PICO’ mnemonic, an acronym for P opulation, I ntervention, C omparison(s) and O utcome. Equal emphasis in addressing, and equal precision in defining, each PICO component is not necessary. For example, a review might concentrate on competing interventions for a particular stage of breast cancer, with stage and severity of the disease being defined very precisely; or alternately focus on a particular drug for any stage of breast cancer, with the treatment formulation being defined very precisely.

Throughout the Handbook we make a distinction between three different stages in the review at which the PICO construct might be used. This division is helpful for understanding the decisions that need to be made:

• The review PICO (planned at the protocol stage) is the PICO on which eligibility of studies is based (what will be included and what excluded from the review).
• The PICO for each synthesis (also planned at the protocol stage) defines the question that each specific synthesis aims to answer, determining how the synthesis will be structured, specifying planned comparisons (including intervention and comparator groups, any grouping of outcome and population subgroups).
• The PICO of the included studies (determined at the review stage) is what was actually investigated in the included studies.

Reaching the point where it is possible to articulate the review’s objectives in the above form – the review PICO – requires time and detailed discussion between potential authors and users of the review. It is important that those involved in developing the review’s scope and questions have a good knowledge of the practical issues that the review will address as well as the research field to be synthesized. Developing the questions is a critical part of the research process. As such, there are methodological issues to bear in mind, including: how to determine which questions are most important to answer; how to engage stakeholders in question formulation; how to account for changes in focus as the review progresses; and considerations about how broad (or narrow) a review should be.

MECIR Box 2.3 . a Relevant expectations for conduct of intervention reviews

2.3.1 Broad versus narrow reviews

The questions addressed by a review may be broad or narrow in scope. For example, a review might address a broad question regarding whether antiplatelet agents in general are effective in preventing all thrombotic events in humans. Alternatively, a review might address whether a particular antiplatelet agent, such as aspirin, is effective in decreasing the risks of a particular thrombotic event, stroke, in elderly persons with a previous history of stroke. Increasingly, reviews are becoming broader, aiming, for example, to identify which intervention – out of a range of treatment options – is most effective, or to investigate how an intervention varies depending on implementation and participant characteristics.

Overviews of reviews (see  Chapter V ), in which multiple reviews are summarized, can be one way of addressing the need for breadth when synthesizing the evidence base, since they can summarize multiple reviews of different interventions for the same condition, or multiple reviews of the same intervention for different types of participants. It may be considered desirable to plan a series of reviews with a relatively narrow scope, alongside an Overview to summarize their findings. Alternatively, it may be more useful – particularly given the growth in support for network meta-analysis – to combine comparisons of different treatment options within the same review (see Chapter 11 ). When deciding whether or not an overview might be the most appropriate approach, review authors should take account of the breadth of the question being asked and the resources available. Some questions are simply too broad for a review of all relevant primary research to be practicable, and if a field has sufficient high-quality reviews, then the production of another review of primary research that duplicates the others might not be a sensible use of resources.

Some of the advantages and disadvantages of broad and narrow reviews are summarized in Table 2.3.a . While having a broad scope in terms of the range of participants has the potential to increase generalizability, the extent to which findings are ultimately applicable to broader (or different) populations will depend on the participants who have actually been recruited into research studies. Likewise, heterogeneity can be a disadvantage when the expectation is for homogeneity of effects between studies, but an advantage when the review question seeks to understand differential effects (see Chapter 10 ).A distinction should be drawn between the scope of a review and the precise questions within, since it is possible to have a broad review that addresses quite narrow questions. In the antiplatelet agents for preventing thrombotic events example, a systematic review with a broad scope might include all available treatments. Rather than combining all the studies into one comparison though, specific treatments would be compared with one another in separate comparisons, thus breaking a heterogeneous set of treatments into narrower, more homogenous groups. This relates to the three levels of PICO, outlined in Section 2.3 . The review PICO defines the broad scope of the review, and the PICO for comparison defines the specific treatments that will be compared with one another; Chapter 3 elaborates on the use of PICOs.

In practice, a Cochrane Review may start (or have started) with a broad scope, and be divided up into narrower reviews as evidence accumulates and the original review becomes unwieldy. This may be done for practical and logistical reasons, for example to make updating easier as well as to make it easier for readers to see which parts of the evidence base are changing. Individual review authors must decide if there are instances where splitting a broader focused review into a series of more narrowly focused reviews is appropriate and implement appropriate methods to achieve this. If a major change is to be undertaken, such as splitting a broad review into a series of more narrowly focused reviews, a new protocol must be written for each of the component reviews that documents the eligibility criteria for each one.

Ultimately, the selected breadth of a review depends upon multiple factors including perspectives regarding a question’s relevance and potential impact; supporting theoretical, biologic and epidemiological information; the potential generalizability and validity of answers to the questions; and available resources. As outlined in Section 2.4.2 , authors should consider carefully the needs of users of the review and the context(s) in which they expect the review to be used when determining the most optimal scope for their review.

Table 2.3.a Some advantages and disadvantages of broad versus narrow reviews

2.3.2 ‘Lumping’ versus ‘splitting’

It is important not to confuse the issue of the breadth of the review (determined by the review PICO) with concerns about between-study heterogeneity and the legitimacy of combining results from diverse studies in the same analysis (determined by the PICOs for comparison).

Broad reviews have been criticized as ‘mixing apples and oranges’, and one of the inventors of meta-analysis, Gene Glass, has responded “Of course it mixes apples and oranges… comparing apples and oranges is the only endeavour worthy of true scientists; comparing apples to apples is trivial” (Glass 2015). In fact, the two concepts (‘broad reviews’ and ‘mixing apples and oranges’) are different issues. Glass argues that broad reviews, with diverse studies, provide the opportunity to ask interesting questions about the reasons for differential intervention effects.

The ‘apples and oranges’ critique refers to the inappropriate mixing of studies within a single comparison, where the purpose is to estimate an average effect. In situations where good biologic or sociological evidence suggests that various formulations of an intervention behave very differently or that various definitions of the condition of interest are associated with markedly different effects of the intervention, the uncritical aggregation of results from quite different interventions or populations/settings may well be questionable.

Unfortunately, determining the situations where studies are similar enough to combine with one another is not always straightforward, and it can depend, to some extent, on the question being asked. While the decision is sometimes characterized as ‘lumping’ (where studies are combined in the same analysis) or ‘splitting’ (where they are not) (Squires et al 2013), it is better to consider these issues on a continuum, with reviews that have greater variation in the types of included interventions, settings and populations, and study designs being towards the ‘lumped’ end, and those that include little variation in these elements being towards the ‘split’ end (Petticrew and Roberts 2006).

While specification of the review PICO sets the boundary for the inclusion and exclusion of studies, decisions also need to be made when planning the PICO for the comparisons to be made in the analysis as to whether they aim to address broader (‘lumped’) or narrower (‘split’) questions (Caldwell and Welton 2016). The degree of ‘lumping’ in the comparisons will be primarily driven by the review’s objectives, but will sometimes be dictated by the availability of studies (and data) for a particular comparison (see Chapter 9 for discussion of the latter). The former is illustrated by a Cochrane Review that examined the effects of newer-generation antidepressants for depressive disorders in children and adolescents (Hetrick et al 2012).

Newer-generation antidepressants include multiple different compounds (e.g. paroxetine, fluoxetine). The objectives of this review were to (i) estimate the overall effect of newer-generation antidepressants on depression, (ii) estimate the effect of each compound, and (iii) examine whether the compound type and age of the participants (children versus adolescents) is associated with the intervention effect. Objective (i) addresses a broad, ‘in principle’ (Caldwell and Welton 2016), question of whether newer-generation antidepressants improve depression, where the different compounds are ‘lumped’ into a single comparison. Objective (ii) seeks to address narrower, ‘split’, questions that investigate the effect of each compound on depression separately. Answers to both questions can be identified by setting up separate comparisons for each compound, or by subgrouping the ‘lumped’ comparison by compound ( Chapter 10, Section 10.11.2 ). Objective (iii) seeks to explore factors that explain heterogeneity among the intervention effects, or equivalently, whether the intervention effect varies by the factor. This can be examined using subgroup analysis or meta-regression ( Chapter 10, Section 10.11 ) but, in the case of intervention types, is best achieved using network meta-analysis (see Chapter 11 ).

There are various advantages and disadvantages to bear in mind when defining the PICO for the comparison and considering whether ‘lumping’ or ‘splitting’ is appropriate. Lumping allows for the investigation of factors that may explain heterogeneity. Results from these investigations may provide important leads as to whether an intervention operates differently in, for example, different populations (such as in children and adolescents in the example above). Ultimately, this type of knowledge is useful for clinical decision making. However, lumping is likely to introduce heterogeneity, which will not always be explained by a priori specified factors, and this may lead to a combined effect that is clinically difficult to interpret and implement. For example, when multiple intervention types are ‘lumped’ in one comparison (as in objective (i) above), and there is unexplained heterogeneity, the combined intervention effect would not enable a clinical decision as to which intervention should be selected. Splitting comparisons carries its own risk of there being too few studies to yield a useful synthesis. Inevitably, some degree of aggregation across the PICO elements is required for a meta-analysis to be undertaken (Caldwell and Welton 2016).

2.4 Ensuring the review addresses the right questions

Since systematic reviews are intended for use in healthcare decision making, review teams should ensure not only the application of robust methodology, but also that the review question is meaningful for healthcare decision making. Two approaches are discussed below:

• Using results from existing research priority-setting exercises to define the review question.
• In the absence of, or in addition to, existing research priority-setting exercises, engaging with stakeholders to define review questions and establish their relevance to policy and practice.

2.4.1 Using priority-setting exercises to define review questions

A research priority-setting exercise is a “collective activity for deciding which uncertainties are most worth trying to resolve through research; uncertainties considered may be problems to be understood or solutions to be developed or tested; across broad or narrow areas” (Sandy Oliver, referenced in Nasser 2018). Using research priority-setting exercises to define the scope of a review helps to prevent the waste of scarce resources for research by making the review more relevant to stakeholders (Chalmers et al 2014).

Research priority setting is always conducted in a specific context, setting and population with specific principles, values and preferences (which should be articulated). Different stakeholders’ interpretation of the scope and purpose of a ‘research question’ might vary, resulting in priorities that might be difficult to interpret. Researchers or review teams might find it necessary to translate the research priorities into an answerable PICO research question format, and may find it useful to recheck the question with the stakeholder groups to determine whether they have accurately reflected their intentions.

While Cochrane Review teams are in most cases reviewing the effects of an intervention with a global scope, they may find that the priorities identified by important stakeholders (such as the World Health Organization or other organizations or individuals in a representative health system) are informative in planning the review. Review authors may find that differences between different stakeholder groups’ views on priorities and the reasons for these differences can help them to define the scope of the review. This is particularly important for making decisions about excluding specific populations or settings, or being inclusive and potentially conducting subgroup analyses.

Whenever feasible, systematic reviews should be based on priorities identified by key stakeholders such as decision makers, patients/public, and practitioners. Cochrane has developed a list of priorities for reviews in consultation with key stakeholders, which is available on the Cochrane website. Issues relating to equity (see Chapter 16 and Section 2.4.3 ) need to be taken into account when conducting and interpreting the results from priority-setting exercises. Examples of materials to support these processes are available (Viergever et al 2010, Nasser et al 2013, Tong et al 2017).

The results of research priority-setting exercises can be searched for in electronic databases and via websites of relevant organizations. Examples are: James Lind Alliance , World Health Organization, organizations of health professionals including research disciplines, and ministries of health in different countries (Viergever 2010). Examples of search strategies for identifying research priority-setting exercises are available (Bryant et al 2014, Tong et al 2015).

Other sources of questions are often found in ‘implications for future research’ sections of articles in journals and clinical practice guidelines. Some guideline developers have prioritized questions identified through the guideline development process (Sharma et al 2018), although these priorities will be influenced by the needs of health systems in which different guideline development teams are working.

2.4.2 Engaging stakeholders to help define the review questions

In the absence of a relevant research priority-setting exercise, or when a systematic review is being conducted for a very specific purpose (for example, commissioned to inform the development of a guideline), researchers should work with relevant stakeholders to define the review question. This practice is especially important when developing review questions for studying the effectiveness of health systems and policies, because of the variability between countries and regions; the significance of these differences may only become apparent through discussion with the stakeholders.

The stakeholders for a review could include consumers or patients, carers, health professionals of different kinds, policy decision makers and others ( Chapter 1, Section 1.3.1 ). Identifying the stakeholders who are critical to a particular question will depend on the question, who the answer is likely to affect, and who will be expected to implement the intervention if it is found to be effective (or to discontinue it if not).

Stakeholder engagement should, optimally, be an ongoing process throughout the life of the systematic review, from defining the question to dissemination of results (Keown et al 2008). Engaging stakeholders increases relevance, promotes mutual learning, improves uptake and decreases research waste (see Chapter 1, Section 1.3.1 and Section 1.3.2 ). However, because such engagement can be challenging and resource intensive, a one-off engagement process to define the review question might only be possible. Review questions that are conceptualized and refined by multiple stakeholders can capture much of the complexity that should be addressed in a systematic review.

2.4.3 Considering issues relating to equity when defining review questions

Deciding what should be investigated, who the participants should be, and how the analysis will be carried out can be considered political activities, with the potential for increasing or decreasing inequalities in health. For example, we now know that well-intended interventions can actually widen inequalities in health outcomes since researchers have chosen to investigate this issue (Lorenc et al 2013). Decision makers can now take account of this knowledge when planning service provision. Authors should therefore consider the potential impact on disadvantaged groups of the intervention(s) that they are investigating on disadvantaged groups, and whether socio-economic inequalities in health might be affected depending on whether or how they are implemented.

Health equity is the absence of avoidable and unfair differences in health (Whitehead 1992). Health inequity may be experienced across characteristics defined by PROGRESS-Plus (Place of residence, Race/ethnicity/culture/language, Occupation, Gender/sex, Religion, Education, Socio-economic status, Social capital, and other characteristics (‘Plus’) such as sexual orientation, age, and disability) (O’Neill et al 2014). Issues relating to health equity should be considered when review questions are developed ( MECIR Box 2.4.a ). Chapter 16 presents detailed guidance on this issue for review authors.

MECIR Box 2.4 . a Relevant expectations for conduct of intervention reviews

2.5 Methods and tools for structuring the review

It is important for authors to develop the scope of their review with care: without a clear understanding of where the review will contribute to existing knowledge – and how it will be used – it may be at risk of conceptual incoherence. It may mis-specify critical elements of how the intervention(s) interact with the context(s) within which they operate to produce specific outcomes, and become either irrelevant or possibly misleading. For example, in a systematic review about smoking cessation interventions in pregnancy, it was essential for authors to take account of the way that health service provision has changed over time. The type and intensity of ‘usual care’ in more recent evaluations was equivalent to the interventions being evaluated in older studies, and the analysis needed to take this into account. This review also found that the same intervention can have different effects in different settings depending on whether its materials are culturally appropriate in each context (Chamberlain et al 2017).

In order to protect the review against conceptual incoherence and irrelevance, review authors need to spend time at the outset developing definitions for key concepts and ensuring that they are clear about the prior assumptions on which the review depends. These prior assumptions include, for example, why particular populations should be considered inside or outside the review’s scope; how the intervention is thought to achieve its effect; and why specific outcomes are selected for evaluation. Being clear about these prior assumptions also requires review authors to consider the evidential basis for these assumptions and decide for themselves which they can place more or less reliance on. When considered as a whole, this initial conceptual and definitional work states the review’s conceptual framework . Each element of the review’s PICO raises its own definitional challenges, which are discussed in detail in the Chapter 3 .

In this section we consider tools that may help to define the scope of the review and the relationships between its key concepts; in particular, articulating how the intervention gives rise to the outcomes selected. In some situations, long sequences of events are expected to occur between an intervention being implemented and an outcome being observed. For example, a systematic review examining the effects of asthma education interventions in schools on children’s health and well-being needed to consider: the interplay between core intervention components and their introduction into differing school environments; different child-level effect modifiers; how the intervention then had an impact on the knowledge of the child (and their family); the child’s self-efficacy and adherence to their treatment regime; the severity of their asthma; the number of days of restricted activity; how this affected their attendance at school; and finally, the distal outcomes of education attainment and indicators of child health and well-being (Kneale et al 2015).

Several specific tools can help authors to consider issues raised when defining review questions and planning their review; these are also helpful when developing eligibility criteria and classifying included studies. These include the following.

• Taxonomies: hierarchical structures that can be used to categorize (or group) related interventions, outcomes or populations.
• Generic frameworks for examining and structuring the description of intervention characteristics (e.g. TIDieR for the description of interventions (Hoffmann et al 2014), iCAT_SR for describing multiple aspects of complexity in systematic reviews (Lewin et al 2017)).
• Core outcome sets for identifying and defining agreed outcomes that should be measured for specific health conditions (described in more detail in Chapter 3 ).

Unlike these tools, which focus on particular aspects of a review, logic models provide a framework for planning and guiding synthesis at the review level (see Section 2.5.1 ).

2.5.1 Logic models

Logic models (sometimes referred to as conceptual frameworks or theories of change) are graphical representations of theories about how interventions work. They depict intervention components, mechanisms (pathways of action), outputs, and outcomes as sequential (although not necessarily linear) chains of events. Among systematic review authors, they were originally proposed as a useful tool when working with evaluations of complex social and population health programmes and interventions, to conceptualize the pathways through which interventions are intended to change outcomes (Anderson et al 2011).

In reviews where intervention complexity is a key consideration (see Chapter 17 ), logic models can be particularly helpful. For example, in a review of psychosocial group interventions for those with HIV, a logic model was used to show how the intervention might work (van der Heijden et al 2017). The review authors depicted proximal outcomes, such as self-esteem, but chose only to include psychological health outcomes in their review. In contrast, Bailey and colleagues included proximal outcomes in their review of computer-based interventions for sexual health promotion using a logic model to show how outcomes were grouped (Bailey et al 2010). Finally, in a review of slum upgrading, a logic model showed the broad range of interventions and their interlinkages with health and socio-economic outcomes (Turley et al 2013), and enabled the review authors to select a specific intervention category (physical upgrading) on which to focus the review. Further resources provide further examples of logic models, and can help review authors develop and use logic models (Anderson et al 2011, Baxter et al 2014, Kneale et al 2015, Pfadenhauer et al 2017, Rohwer et al 2017).

Logic models can vary in their emphasis, with a distinction sometimes made between system-based and process-oriented logic models (Rehfuess et al 2018). System-based logic models have particular value in examining the complexity of the system (e.g. the geographical, epidemiological, political, socio-cultural and socio-economic features of a system), and the interactions between contextual features, participants and the intervention (see Chapter 17 ). Process-oriented logic models aim to capture the complexity of causal pathways by which the intervention leads to outcomes, and any factors that may modify intervention effects. However, this is not a crisp distinction; the two types are interrelated; with some logic models depicting elements of both systems and process models simultaneously.

The way that logic models can be represented diagrammatically (see Chapter 17 for an example) provides a valuable visual summary for readers and can be a communication tool for decision makers and practitioners. They can aid initially in the development of a shared understanding between different stakeholders of the scope of the review and its PICO, helping to support decisions taken throughout the review process, from developing the research question and setting the review parameters, to structuring and interpreting the results. They can be used in planning the PICO elements of a review as well as for determining how the synthesis will be structured (i.e. planned comparisons, including intervention and comparator groups, and any grouping of outcome and population subgroups). These models may help review authors specify the link between the intervention, proximal and distal outcomes, and mediating factors. In other words, they depict the intervention theory underpinning the synthesis plan.

Anderson and colleagues note the main value of logic models in systematic review as (Anderson et al 2011):

• refining review questions;
• deciding on ‘lumping’ or ‘splitting’ a review topic;
• identifying intervention components;
• defining and conducting the review;
• identifying relevant study eligibility criteria;
• guiding the literature search strategy;
• explaining the rationale behind surrogate outcomes used in the review;
• justifying the need for subgroup analyses (e.g. age, sex/gender, socio-economic status);
• making the review relevant to policy and practice;
• structuring the reporting of results;
• illustrating how harms and feasibility are connected with interventions; and
• interpreting results based on intervention theory and systems thinking (see Chapter 17 ).

Logic models can be useful in systematic reviews when considering whether failure to find a beneficial effect of an intervention is due to a theory failure, an implementation failure, or both (see Chapter 17 and Cargo et al 2018). Making a distinction between implementation and intervention theory can help to determine whether and how the intervention interacts with (and potentially changes) its context (see Chapter 3 and Chapter 17 for further discussion of context). This helps to elucidate situations in which variations in how the intervention is implemented have the potential to affect the integrity of the intervention and intended outcomes.

Given their potential value in conceptualizing and structuring a review, logic models are increasingly published in review protocols. Logic models may be specified a priori and remain unchanged throughout the review; it might be expected, however, that the findings of reviews produce evidence and new understandings that could be used to update the logic model in some way (Kneale et al 2015). Some reviews take a more staged approach, pre-specifying points in the review process where the model may be revised on the basis of (new) evidence (Rehfuess et al 2018) and a staged logic model can provide an efficient way to report revisions to the synthesis plan. For example, in a review of portion, package and tableware size for changing selection or consumption of food and other products, the authors presented a logic model that clearly showed changes to their original synthesis plan (Hollands et al 2015).

It is preferable to seek out existing logic models for the intervention and revise or adapt these models in line with the review focus, although this may not always be possible. More commonly, new models are developed starting with the identification of outcomes and theorizing the necessary pre-conditions to reach those outcomes. This process of theorizing and identifying the steps and necessary pre-conditions continues, working backwards from the intended outcomes, until the intervention itself is represented. As many mechanisms of action are invisible and can only be ‘known’ through theory, this process is invaluable in exposing assumptions as to how interventions are thought to work; assumptions that might then be tested in the review. Logic models can be developed with stakeholders (see Section 2.5.2 ) and it is considered good practice to obtain stakeholder input in their development.

Logic models are representations of how interventions are intended to ‘work’, but they can also provide a useful basis for thinking through the unintended consequences of interventions and identifying potential adverse effects that may need to be captured in the review (Bonell et al 2015). While logic models provide a guiding theory of how interventions are intended to work, critiques exist around their use, including their potential to oversimplify complex intervention processes (Rohwer et al 2017). Here, contributions from different stakeholders to the development of a logic model may be able to articulate where complex processes may occur; theorizing unintended intervention impacts; and the explicit representation of ambiguity within certain parts of the causal chain where new theory/explanation is most valuable.

2.5.2 Changing review questions

While questions should be posed in the protocol before initiating the full review, these questions should not prevent exploration of unexpected issues. Reviews are analyses of existing data that are constrained by previously chosen study populations, settings, intervention formulations, outcome measures and study designs. It is generally not possible to formulate an answerable question for a review without knowing some of the studies relevant to the question, and it may become clear that the questions a review addresses need to be modified in light of evidence accumulated in the process of conducting the review.

Although a certain fluidity and refinement of questions is to be expected in reviews as a fuller understanding of the evidence is gained, it is important to guard against bias in modifying questions. Data-driven questions can generate false conclusions based on spurious results. Any changes to the protocol that result from revising the question for the review should be documented at the beginning of the Methods section. Sensitivity analyses may be used to assess the impact of changes on the review findings (see Chapter 10, Section 10.14 ). When refining questions it is useful to ask the following questions.

• What is the motivation for the refinement?
• Could the refinement have been influenced by results from any of the included studies?
• Does the refined question require a modification to the search strategy and/or reassessment of any decisions regarding study eligibility?
• Are data collection methods appropriate to the refined question?
• Does the refined question still meet the FINER criteria discussed in Section 2.1 ?

2.5.3 Building in contingencies to deal with sparse data

The ability to address the review questions will depend on the maturity and validity of the evidence base. When few studies are identified, there will be limited opportunity to address the question through an informative synthesis. In anticipation of this scenario, review authors may build contingencies into their protocol analysis plan that specify grouping (any or multiple) PICO elements at a broader level; thus potentially enabling synthesis of a larger number of studies. Broader groupings will generally address a less specific question, for example:

• ‘the effect of any antioxidant supplement on …’ instead of ‘the effect of vitamin C on …’;
• ‘the effect of sexual health promotion on biological outcomes ’ instead of ‘the effect of sexual health promotion on sexually transmitted infections ’; or
• ‘the effect of cognitive behavioural therapy in children and adolescents on …’ instead of ‘the effect of cognitive behavioural therapy in children on …’.

However, such broader questions may be useful for identifying important leads in areas that lack effective interventions and for guiding future research. Changes in the grouping may affect the assessment of the certainty of the evidence (see Chapter 14 ).

2.5.4 Economic data

Decision makers need to consider the economic aspects of an intervention, such as whether its adoption will lead to a more efficient use of resources. Economic data such as resource use, costs or cost-effectiveness (or a combination of these) may therefore be included as outcomes in a review. It is useful to break down measures of resource use and costs to the level of specific items or categories. It is helpful to consider an international perspective in the discussion of costs. Economics issues are discussed in detail in Chapter 20 .

2.6 Chapter information

Authors: James Thomas, Dylan Kneale, Joanne E McKenzie, Sue E Brennan, Soumyadeep Bhaumik

Acknowledgements: This chapter builds on earlier versions of the Handbook . Mona Nasser, Dan Fox and Sally Crowe contributed to Section 2.4 ; Hilary J Thomson contributed to Section 2.5.1 .

Funding: JT and DK are supported by the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care North Thames at Barts Health NHS Trust. JEM is supported by an Australian National Health and Medical Research Council (NHMRC) Career Development Fellowship (1143429). SEB’s position is supported by the NHMRC Cochrane Collaboration Funding Program. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the Department of Health or the NHMRC.

2.7 References

Anderson L, Petticrew M, Rehfuess E, Armstrong R, Ueffing E, Baker P, Francis D, Tugwell P. Using logic models to capture complexity in systematic reviews. Research Synthesis Methods 2011; 2 : 33–42.

Bailey JV, Murray E, Rait G, Mercer CH, Morris RW, Peacock R, Cassell J, Nazareth I. Interactive computer-based interventions for sexual health promotion. Cochrane Database of Systematic Reviews 2010; 9 : CD006483.

Baxter SK, Blank L, Woods HB, Payne N, Rimmer M, Goyder E. Using logic model methods in systematic review synthesis: describing complex pathways in referral management interventions. BMC Medical Research Methodology 2014; 14 : 62.

Bonell C, Jamal F, Melendez-Torres GJ, Cummins S. ‘Dark logic’: theorising the harmful consequences of public health interventions. Journal of Epidemiology and Community Health 2015; 69 : 95–98.

Bryant J, Sanson-Fisher R, Walsh J, Stewart J. Health research priority setting in selected high income countries: a narrative review of methods used and recommendations for future practice. Cost Effectiveness and Resource Allocation 2014; 12 : 23.

Caldwell DM, Welton NJ. Approaches for synthesising complex mental health interventions in meta-analysis. Evidence-Based Mental Health 2016; 19 : 16–21.

Cargo M, Harris J, Pantoja T, Booth A, Harden A, Hannes K, Thomas J, Flemming K, Garside R, Noyes J. Cochrane Qualitative and Implementation Methods Group guidance series-paper 4: methods for assessing evidence on intervention implementation. Journal of Clinical Epidemiology 2018; 97 : 59–69.

Chalmers I, Bracken MB, Djulbegovic B, Garattini S, Grant J, Gülmezoglu AM, Howells DW, Ioannidis JPA, Oliver S. How to increase value and reduce waste when research priorities are set. Lancet 2014; 383 : 156–165.

Chamberlain C, O’Mara-Eves A, Porter J, Coleman T, Perlen S, Thomas J, McKenzie J. Psychosocial interventions for supporting women to stop smoking in pregnancy. Cochrane Database of Systematic Reviews 2017; 2 : CD001055.

Cooper H. The problem formulation stage. In: Cooper H, editor. Integrating Research: A Guide for Literature Reviews . Newbury Park (CA) USA: Sage Publications; 1984.

Counsell C. Formulating questions and locating primary studies for inclusion in systematic reviews. Annals of Internal Medicine 1997; 127 : 380–387.

Cummings SR, Browner WS, Hulley SB. Conceiving the research question and developing the study plan. In: Hulley SB, Cummings SR, Browner WS, editors. Designing Clinical Research: An Epidemiological Approach . 4th ed. Philadelphia (PA): Lippincott Williams & Wilkins; 2007. p. 14–22.

Glass GV. Meta-analysis at middle age: a personal history. Research Synthesis Methods 2015; 6 : 221–231.

Hedges LV. Statistical considerations. In: Cooper H, Hedges LV, editors. The Handbook of Research Synthesis . New York (NY): USA: Russell Sage Foundation; 1994.

Hetrick SE, McKenzie JE, Cox GR, Simmons MB, Merry SN. Newer generation antidepressants for depressive disorders in children and adolescents. Cochrane Database of Systematic Reviews 2012; 11 : CD004851.

Hoffmann T, Glasziou P, Boutron I. Better reporting of interventions: template for intervention description and replication (TIDieR) checklist and guide. BMJ 2014; 348: g1687.

Hollands GJ, Shemilt I, Marteau TM, Jebb SA, Lewis HB, Wei Y, Higgins JPT, Ogilvie D. Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Cochrane Database of Systematic Reviews 2015; 9 : CD011045.

Keown K, Van Eerd D, Irvin E. Stakeholder engagement opportunities in systematic reviews: Knowledge transfer for policy and practice. Journal of Continuing Education in the Health Professions 2008; 28 : 67–72.

Kneale D, Thomas J, Harris K. Developing and optimising the use of logic models in systematic reviews: exploring practice and good practice in the use of programme theory in reviews. PloS One 2015; 10 : e0142187.

Lewin S, Hendry M, Chandler J, Oxman AD, Michie S, Shepperd S, Reeves BC, Tugwell P, Hannes K, Rehfuess EA, Welch V, McKenzie JE, Burford B, Petkovic J, Anderson LM, Harris J, Noyes J. Assessing the complexity of interventions within systematic reviews: development, content and use of a new tool (iCAT_SR). BMC Medical Research Methodology 2017; 17 : 76.

Lorenc T, Petticrew M, Welch V, Tugwell P. What types of interventions generate inequalities? Evidence from systematic reviews. Journal of Epidemiology and Community Health 2013; 67 : 190–193.

Nasser M, Ueffing E, Welch V, Tugwell P. An equity lens can ensure an equity-oriented approach to agenda setting and priority setting of Cochrane Reviews. Journal of Clinical Epidemiology 2013; 66 : 511–521.

Nasser M. Setting priorities for conducting and updating systematic reviews [PhD Thesis]: University of Plymouth; 2018.

O’Neill J, Tabish H, Welch V, Petticrew M, Pottie K, Clarke M, Evans T, Pardo Pardo J, Waters E, White H, Tugwell P. Applying an equity lens to interventions: using PROGRESS ensures consideration of socially stratifying factors to illuminate inequities in health. Journal of Clinical Epidemiology 2014; 67 : 56–64.

Oliver S, Dickson K, Bangpan M, Newman M. Getting started with a review. In: Gough D, Oliver S, Thomas J, editors. An Introduction to Systematic Reviews . London (UK): Sage Publications Ltd.; 2017.

Petticrew M, Roberts H. Systematic Reviews in the Social Sciences: A Practical Guide . Oxford (UK): Blackwell; 2006.

Pfadenhauer L, Gerhardus A, Mozygemba K, Lysdahl KB, Booth A, Hofmann B, Wahlster P, Polus S, Burns J, Brereton L, Rehfuess E. Making sense of complexity in context and implementation: the Context and Implementation of Complex Interventions (CICI) framework. Implementation Science 2017; 12 : 21.

Rehfuess EA, Booth A, Brereton L, Burns J, Gerhardus A, Mozygemba K, Oortwijn W, Pfadenhauer LM, Tummers M, van der Wilt GJ, Rohwer A. Towards a taxonomy of logic models in systematic reviews and health technology assessments: a priori, staged, and iterative approaches. Research Synthesis Methods 2018; 9 : 13–24.

Richardson WS, Wilson MC, Nishikawa J, Hayward RS. The well-built clinical question: a key to evidence-based decisions. ACP Journal Club 1995; 123 : A12–13.

Rohwer A, Pfadenhauer L, Burns J, Brereton L, Gerhardus A, Booth A, Oortwijn W, Rehfuess E. Series: Clinical epidemiology in South Africa. Paper 3: Logic models help make sense of complexity in systematic reviews and health technology assessments. Journal of Clinical Epidemiology 2017; 83 : 37–47.

Sharma T, Choudhury M, Rejón-Parrilla JC, Jonsson P, Garner S. Using HTA and guideline development as a tool for research priority setting the NICE way: reducing research waste by identifying the right research to fund. BMJ Open 2018; 8 : e019777.

Squires J, Valentine J, Grimshaw J. Systematic reviews of complex interventions: framing the review question. Journal of Clinical Epidemiology 2013; 66 : 1215–1222.

Tong A, Chando S, Crowe S, Manns B, Winkelmayer WC, Hemmelgarn B, Craig JC. Research priority setting in kidney disease: a systematic review. American Journal of Kidney Diseases 2015; 65 : 674–683.

Tong A, Sautenet B, Chapman JR, Harper C, MacDonald P, Shackel N, Crowe S, Hanson C, Hill S, Synnot A, Craig JC. Research priority setting in organ transplantation: a systematic review. Transplant International 2017; 30 : 327–343.

Turley R, Saith R, Bhan N, Rehfuess E, Carter B. Slum upgrading strategies involving physical environment and infrastructure interventions and their effects on health and socio-economic outcomes. Cochrane Database of Systematic Reviews 2013; 1 : CD010067.

van der Heijden I, Abrahams N, Sinclair D. Psychosocial group interventions to improve psychological well-being in adults living with HIV. Cochrane Database of Systematic Reviews 2017; 3 : CD010806.

Viergever RF. Health Research Prioritization at WHO: An Overview of Methodology and High Level Analysis of WHO Led Health Research Priority Setting Exercises . Geneva (Switzerland): World Health Organization; 2010.

Viergever RF, Olifson S, Ghaffar A, Terry RF. A checklist for health research priority setting: nine common themes of good practice. Health Research Policy and Systems 2010; 8 : 36.

Whitehead M. The concepts and principles of equity and health. International Journal of Health Services 1992; 22 : 429–25.

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• Library databases
• Library website

Library Guide to Capstone Literature Reviews: Scope

Introduction.

When working on your literature review, you will read and look at hundreds of articles, books, and other materials. However, you will not include all of them in your final literature review. This does not mean you've wasted your time looking at unnecessary articles! Rather, this review of the literature is what helps you become an expert in your field.

On this page you will learn more about:

• what types of sources to include in or use for your literature review
• how to find current research
• how to identify and locate peer-reviewed articles

For additional information on the scope of your literature review, please see this guide from the Writing Center:

• Literature Review: Setting a Broad Scope

Most of what you include in your literature review will be peer-reviewed journal articles. However, other sources may be appropriate to include in your literature review as well. You will need to consult and be familiar with some resources, like dissertations, even though you will not typically use them as a source in your literature review.

Foundational literature

Foundational literature, also referred to as seminal research, is the original or groundbreaking work in your area of study.

• This includes the literature and theorist(s) that developed or first wrote about a concept or theory.
• Foundational literature will generally be older than five years and may have been published in a book, and not in a peer-reviewed journal.
• While it is important to show that you are aware of the foundational literature in your field, it will not make up a huge section of your literature review. Resist the urge to make your literature review a history lesson.

Authoritative sources 

Authoritative sources are reputable institutions that produce reports and data that are accepted as accurate and reliable. Their publications do not generally go through a standard academic peer-review process. These are some examples:

• Census data
• Department of Education statistics
• Centers for Disease Control and Prevention reports
• American Psychological Association
• Pew Research Center

Dissertations

Dissertations are great resources to use, but you will typically not be able to cite them in your own dissertation.

• You want to be aware of dissertations on a similar or related topic because you will need to understand how your research builds on, or is different from existing research.
• Dissertations can be great resources for seeing what instruments were used, or what sources were cited. You can then use that information to locate the original instrument, research article, book, etc.

Background materials

There are other helpful sources that you may refer to when doing research  that will not be a part of your final literature review. They include:

To learn more about evaluating the resources you find, please see the Library's Evaluating Resources guide:

• Guide: Evaluating Resources Evaluation criteria and tips for the scholarly researcher.

Publication years

Much of your literature review will focus on the current research being done in your field, meaning research conducted within the last five years. However, the foundational or seminal research in your field is almost always older than five years.

In order to make sure you are a well-informed scholar, it is a good practice to begin your research without limiting your searches by date.

Once you are familiar with the research in your field, you can focus your searches on only those items that were published within the last five years.

Most of the Library databases have an option to limit your results to a certain time frame. Please refer to the Keyword Searching guide to learn how to limit by date:

• Keyword Searching: Limit by Publication Date
• Peer Review

Peer review is a specific quality control process that journal publishers use to ensure that what they publish is accurate and reliable. Most of the sources that you include in your literature review will be from journals that use a peer review process. To learn more about peer review, please see our Peer Review guide:

If you need to verify that an article is from a peer-reviewed source, you can do so with Ulrich's Periodicals Directory . Here is a guide that will help you learn how to use Ulrich's:

• Guide: Verify peer review

To learn more about different types of academic resources that are published, please see the Publication Comparison Chart:

• Publication Comparison Chart

You can check your program's peer review requirements by visiting the Office of Student Research Administration website:

• Office of Student Research Administration
• Previous Page: Role of the Literature Review
• Next Page: Find a Research Gap
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What are scoping reviews? Providing a formal definition of scoping reviews as a type of evidence synthesis

Affiliations.

• 1 JBI, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide, SA, Australia.
• 2 La Trobe University, School of Psychology and Public Health, Department of Public Health, Melbourne, VIC, Australia.
• 3 School of Health Sciences, Robert Gordon University, Aberdeen, UK.
• 4 The Scottish Centre for Evidence-based, Multi-professional Practice: A JBI Centre of Excellence, Aberdeen, UK.
• 5 The Wits-JBI Centre for Evidenced-Based Practice: A JBI Affiliated Group, University of the Witwa-tersrand, Johannesburg, South Africa.
• 6 Queen's Collaboration for Health Care Quality: A JBI Centre of Excellence, Queen's University School of Nursing, Kingston, ON, Canada.
• 7 University of South Australia, Clinical and Health Sciences, Rosemary Bryant AO Research Centre, Adelaide, SA, Australia.
• 8 Adelaide Nursing School, Faculty of Health and Medical Sciences, The University of Adelaide, Adelaide, SA, Australia.
• 9 The Centre for Evidence-based Practice South Australia (CEPSA): A JBI Centre of Excellence, The University of Adelaide, Adelaide, SA, Australia.
• 10 Li Ka Shing Knowledge Institute, St. Michael's Hospital, Unity Health Toronto, Toronto, ON, Canada.
• 11 Epidemiology Division and Institute of Health Policy, Management, and Evaluation, Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
• PMID: 35249995
• DOI: 10.11124/JBIES-21-00483

Evidence synthesis encompasses a broad range of review types, and scoping reviews are an increasingly popular approach to synthesizing evidence in a number of fields. They sit alongside other evidence synthesis methodologies, such as systematic reviews, qualitative evidence synthesis, realist synthesis, and many more. Until now, scoping reviews have been variously defined in the literature. In this article, we provide the following formal definition for scoping reviews: Scoping reviews are a type of evidence synthesis that aims to systematically identify and map the breadth of evidence available on a particular topic, field, concept, or issue, often irrespective of source (ie, primary research, reviews, non-empirical evidence) within or across particular contexts. Scoping reviews can clarify key concepts/definitions in the literature and identify key characteristics or factors related to a concept, including those related to methodological research.

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Lau F, Kuziemsky C, editors. Handbook of eHealth Evaluation: An Evidence-based Approach [Internet]. Victoria (BC): University of Victoria; 2017 Feb 27.

Handbook of eHealth Evaluation: An Evidence-based Approach [Internet].

Chapter 9 methods for literature reviews.

Guy Paré and Spyros Kitsiou .

9.1. Introduction

Literature reviews play a critical role in scholarship because science remains, first and foremost, a cumulative endeavour ( vom Brocke et al., 2009 ). As in any academic discipline, rigorous knowledge syntheses are becoming indispensable in keeping up with an exponentially growing eHealth literature, assisting practitioners, academics, and graduate students in finding, evaluating, and synthesizing the contents of many empirical and conceptual papers. Among other methods, literature reviews are essential for: (a) identifying what has been written on a subject or topic; (b) determining the extent to which a specific research area reveals any interpretable trends or patterns; (c) aggregating empirical findings related to a narrow research question to support evidence-based practice; (d) generating new frameworks and theories; and (e) identifying topics or questions requiring more investigation ( Paré, Trudel, Jaana, & Kitsiou, 2015 ).

Literature reviews can take two major forms. The most prevalent one is the “literature review” or “background” section within a journal paper or a chapter in a graduate thesis. This section synthesizes the extant literature and usually identifies the gaps in knowledge that the empirical study addresses ( Sylvester, Tate, & Johnstone, 2013 ). It may also provide a theoretical foundation for the proposed study, substantiate the presence of the research problem, justify the research as one that contributes something new to the cumulated knowledge, or validate the methods and approaches for the proposed study ( Hart, 1998 ; Levy & Ellis, 2006 ).

The second form of literature review, which is the focus of this chapter, constitutes an original and valuable work of research in and of itself ( Paré et al., 2015 ). Rather than providing a base for a researcher’s own work, it creates a solid starting point for all members of the community interested in a particular area or topic ( Mulrow, 1987 ). The so-called “review article” is a journal-length paper which has an overarching purpose to synthesize the literature in a field, without collecting or analyzing any primary data ( Green, Johnson, & Adams, 2006 ).

When appropriately conducted, review articles represent powerful information sources for practitioners looking for state-of-the art evidence to guide their decision-making and work practices ( Paré et al., 2015 ). Further, high-quality reviews become frequently cited pieces of work which researchers seek out as a first clear outline of the literature when undertaking empirical studies ( Cooper, 1988 ; Rowe, 2014 ). Scholars who track and gauge the impact of articles have found that review papers are cited and downloaded more often than any other type of published article ( Cronin, Ryan, & Coughlan, 2008 ; Montori, Wilczynski, Morgan, Haynes, & Hedges, 2003 ; Patsopoulos, Analatos, & Ioannidis, 2005 ). The reason for their popularity may be the fact that reading the review enables one to have an overview, if not a detailed knowledge of the area in question, as well as references to the most useful primary sources ( Cronin et al., 2008 ). Although they are not easy to conduct, the commitment to complete a review article provides a tremendous service to one’s academic community ( Paré et al., 2015 ; Petticrew & Roberts, 2006 ). Most, if not all, peer-reviewed journals in the fields of medical informatics publish review articles of some type.

The main objectives of this chapter are fourfold: (a) to provide an overview of the major steps and activities involved in conducting a stand-alone literature review; (b) to describe and contrast the different types of review articles that can contribute to the eHealth knowledge base; (c) to illustrate each review type with one or two examples from the eHealth literature; and (d) to provide a series of recommendations for prospective authors of review articles in this domain.

9.2. Overview of the Literature Review Process and Steps

As explained in Templier and Paré (2015) , there are six generic steps involved in conducting a review article:

• formulating the research question(s) and objective(s),
• searching the extant literature,
• screening for inclusion,
• assessing the quality of primary studies,
• extracting data, and
• analyzing data.

Although these steps are presented here in sequential order, one must keep in mind that the review process can be iterative and that many activities can be initiated during the planning stage and later refined during subsequent phases ( Finfgeld-Connett & Johnson, 2013 ; Kitchenham & Charters, 2007 ).

Formulating the research question(s) and objective(s): As a first step, members of the review team must appropriately justify the need for the review itself ( Petticrew & Roberts, 2006 ), identify the review’s main objective(s) ( Okoli & Schabram, 2010 ), and define the concepts or variables at the heart of their synthesis ( Cooper & Hedges, 2009 ; Webster & Watson, 2002 ). Importantly, they also need to articulate the research question(s) they propose to investigate ( Kitchenham & Charters, 2007 ). In this regard, we concur with Jesson, Matheson, and Lacey (2011) that clearly articulated research questions are key ingredients that guide the entire review methodology; they underscore the type of information that is needed, inform the search for and selection of relevant literature, and guide or orient the subsequent analysis. Searching the extant literature: The next step consists of searching the literature and making decisions about the suitability of material to be considered in the review ( Cooper, 1988 ). There exist three main coverage strategies. First, exhaustive coverage means an effort is made to be as comprehensive as possible in order to ensure that all relevant studies, published and unpublished, are included in the review and, thus, conclusions are based on this all-inclusive knowledge base. The second type of coverage consists of presenting materials that are representative of most other works in a given field or area. Often authors who adopt this strategy will search for relevant articles in a small number of top-tier journals in a field ( Paré et al., 2015 ). In the third strategy, the review team concentrates on prior works that have been central or pivotal to a particular topic. This may include empirical studies or conceptual papers that initiated a line of investigation, changed how problems or questions were framed, introduced new methods or concepts, or engendered important debate ( Cooper, 1988 ). Screening for inclusion: The following step consists of evaluating the applicability of the material identified in the preceding step ( Levy & Ellis, 2006 ; vom Brocke et al., 2009 ). Once a group of potential studies has been identified, members of the review team must screen them to determine their relevance ( Petticrew & Roberts, 2006 ). A set of predetermined rules provides a basis for including or excluding certain studies. This exercise requires a significant investment on the part of researchers, who must ensure enhanced objectivity and avoid biases or mistakes. As discussed later in this chapter, for certain types of reviews there must be at least two independent reviewers involved in the screening process and a procedure to resolve disagreements must also be in place ( Liberati et al., 2009 ; Shea et al., 2009 ). Assessing the quality of primary studies: In addition to screening material for inclusion, members of the review team may need to assess the scientific quality of the selected studies, that is, appraise the rigour of the research design and methods. Such formal assessment, which is usually conducted independently by at least two coders, helps members of the review team refine which studies to include in the final sample, determine whether or not the differences in quality may affect their conclusions, or guide how they analyze the data and interpret the findings ( Petticrew & Roberts, 2006 ). Ascribing quality scores to each primary study or considering through domain-based evaluations which study components have or have not been designed and executed appropriately makes it possible to reflect on the extent to which the selected study addresses possible biases and maximizes validity ( Shea et al., 2009 ). Extracting data: The following step involves gathering or extracting applicable information from each primary study included in the sample and deciding what is relevant to the problem of interest ( Cooper & Hedges, 2009 ). Indeed, the type of data that should be recorded mainly depends on the initial research questions ( Okoli & Schabram, 2010 ). However, important information may also be gathered about how, when, where and by whom the primary study was conducted, the research design and methods, or qualitative/quantitative results ( Cooper & Hedges, 2009 ). Analyzing and synthesizing data : As a final step, members of the review team must collate, summarize, aggregate, organize, and compare the evidence extracted from the included studies. The extracted data must be presented in a meaningful way that suggests a new contribution to the extant literature ( Jesson et al., 2011 ). Webster and Watson (2002) warn researchers that literature reviews should be much more than lists of papers and should provide a coherent lens to make sense of extant knowledge on a given topic. There exist several methods and techniques for synthesizing quantitative (e.g., frequency analysis, meta-analysis) and qualitative (e.g., grounded theory, narrative analysis, meta-ethnography) evidence ( Dixon-Woods, Agarwal, Jones, Young, & Sutton, 2005 ; Thomas & Harden, 2008 ).

9.3. Types of Review Articles and Brief Illustrations

EHealth researchers have at their disposal a number of approaches and methods for making sense out of existing literature, all with the purpose of casting current research findings into historical contexts or explaining contradictions that might exist among a set of primary research studies conducted on a particular topic. Our classification scheme is largely inspired from Paré and colleagues’ (2015) typology. Below we present and illustrate those review types that we feel are central to the growth and development of the eHealth domain.

9.3.1. Narrative Reviews

The narrative review is the “traditional” way of reviewing the extant literature and is skewed towards a qualitative interpretation of prior knowledge ( Sylvester et al., 2013 ). Put simply, a narrative review attempts to summarize or synthesize what has been written on a particular topic but does not seek generalization or cumulative knowledge from what is reviewed ( Davies, 2000 ; Green et al., 2006 ). Instead, the review team often undertakes the task of accumulating and synthesizing the literature to demonstrate the value of a particular point of view ( Baumeister & Leary, 1997 ). As such, reviewers may selectively ignore or limit the attention paid to certain studies in order to make a point. In this rather unsystematic approach, the selection of information from primary articles is subjective, lacks explicit criteria for inclusion and can lead to biased interpretations or inferences ( Green et al., 2006 ). There are several narrative reviews in the particular eHealth domain, as in all fields, which follow such an unstructured approach ( Silva et al., 2015 ; Paul et al., 2015 ).

Despite these criticisms, this type of review can be very useful in gathering together a volume of literature in a specific subject area and synthesizing it. As mentioned above, its primary purpose is to provide the reader with a comprehensive background for understanding current knowledge and highlighting the significance of new research ( Cronin et al., 2008 ). Faculty like to use narrative reviews in the classroom because they are often more up to date than textbooks, provide a single source for students to reference, and expose students to peer-reviewed literature ( Green et al., 2006 ). For researchers, narrative reviews can inspire research ideas by identifying gaps or inconsistencies in a body of knowledge, thus helping researchers to determine research questions or formulate hypotheses. Importantly, narrative reviews can also be used as educational articles to bring practitioners up to date with certain topics of issues ( Green et al., 2006 ).

Recently, there have been several efforts to introduce more rigour in narrative reviews that will elucidate common pitfalls and bring changes into their publication standards. Information systems researchers, among others, have contributed to advancing knowledge on how to structure a “traditional” review. For instance, Levy and Ellis (2006) proposed a generic framework for conducting such reviews. Their model follows the systematic data processing approach comprised of three steps, namely: (a) literature search and screening; (b) data extraction and analysis; and (c) writing the literature review. They provide detailed and very helpful instructions on how to conduct each step of the review process. As another methodological contribution, vom Brocke et al. (2009) offered a series of guidelines for conducting literature reviews, with a particular focus on how to search and extract the relevant body of knowledge. Last, Bandara, Miskon, and Fielt (2011) proposed a structured, predefined and tool-supported method to identify primary studies within a feasible scope, extract relevant content from identified articles, synthesize and analyze the findings, and effectively write and present the results of the literature review. We highly recommend that prospective authors of narrative reviews consult these useful sources before embarking on their work.

Darlow and Wen (2015) provide a good example of a highly structured narrative review in the eHealth field. These authors synthesized published articles that describe the development process of mobile health ( m-health ) interventions for patients’ cancer care self-management. As in most narrative reviews, the scope of the research questions being investigated is broad: (a) how development of these systems are carried out; (b) which methods are used to investigate these systems; and (c) what conclusions can be drawn as a result of the development of these systems. To provide clear answers to these questions, a literature search was conducted on six electronic databases and Google Scholar . The search was performed using several terms and free text words, combining them in an appropriate manner. Four inclusion and three exclusion criteria were utilized during the screening process. Both authors independently reviewed each of the identified articles to determine eligibility and extract study information. A flow diagram shows the number of studies identified, screened, and included or excluded at each stage of study selection. In terms of contributions, this review provides a series of practical recommendations for m-health intervention development.

9.3.2. Descriptive or Mapping Reviews

The primary goal of a descriptive review is to determine the extent to which a body of knowledge in a particular research topic reveals any interpretable pattern or trend with respect to pre-existing propositions, theories, methodologies or findings ( King & He, 2005 ; Paré et al., 2015 ). In contrast with narrative reviews, descriptive reviews follow a systematic and transparent procedure, including searching, screening and classifying studies ( Petersen, Vakkalanka, & Kuzniarz, 2015 ). Indeed, structured search methods are used to form a representative sample of a larger group of published works ( Paré et al., 2015 ). Further, authors of descriptive reviews extract from each study certain characteristics of interest, such as publication year, research methods, data collection techniques, and direction or strength of research outcomes (e.g., positive, negative, or non-significant) in the form of frequency analysis to produce quantitative results ( Sylvester et al., 2013 ). In essence, each study included in a descriptive review is treated as the unit of analysis and the published literature as a whole provides a database from which the authors attempt to identify any interpretable trends or draw overall conclusions about the merits of existing conceptualizations, propositions, methods or findings ( Paré et al., 2015 ). In doing so, a descriptive review may claim that its findings represent the state of the art in a particular domain ( King & He, 2005 ).

In the fields of health sciences and medical informatics, reviews that focus on examining the range, nature and evolution of a topic area are described by Anderson, Allen, Peckham, and Goodwin (2008) as mapping reviews . Like descriptive reviews, the research questions are generic and usually relate to publication patterns and trends. There is no preconceived plan to systematically review all of the literature although this can be done. Instead, researchers often present studies that are representative of most works published in a particular area and they consider a specific time frame to be mapped.

An example of this approach in the eHealth domain is offered by DeShazo, Lavallie, and Wolf (2009). The purpose of this descriptive or mapping review was to characterize publication trends in the medical informatics literature over a 20-year period (1987 to 2006). To achieve this ambitious objective, the authors performed a bibliometric analysis of medical informatics citations indexed in medline using publication trends, journal frequencies, impact factors, Medical Subject Headings (MeSH) term frequencies, and characteristics of citations. Findings revealed that there were over 77,000 medical informatics articles published during the covered period in numerous journals and that the average annual growth rate was 12%. The MeSH term analysis also suggested a strong interdisciplinary trend. Finally, average impact scores increased over time with two notable growth periods. Overall, patterns in research outputs that seem to characterize the historic trends and current components of the field of medical informatics suggest it may be a maturing discipline (DeShazo et al., 2009).

9.3.3. Scoping Reviews

Scoping reviews attempt to provide an initial indication of the potential size and nature of the extant literature on an emergent topic (Arksey & O’Malley, 2005; Daudt, van Mossel, & Scott, 2013 ; Levac, Colquhoun, & O’Brien, 2010). A scoping review may be conducted to examine the extent, range and nature of research activities in a particular area, determine the value of undertaking a full systematic review (discussed next), or identify research gaps in the extant literature ( Paré et al., 2015 ). In line with their main objective, scoping reviews usually conclude with the presentation of a detailed research agenda for future works along with potential implications for both practice and research.

Unlike narrative and descriptive reviews, the whole point of scoping the field is to be as comprehensive as possible, including grey literature (Arksey & O’Malley, 2005). Inclusion and exclusion criteria must be established to help researchers eliminate studies that are not aligned with the research questions. It is also recommended that at least two independent coders review abstracts yielded from the search strategy and then the full articles for study selection ( Daudt et al., 2013 ). The synthesized evidence from content or thematic analysis is relatively easy to present in tabular form (Arksey & O’Malley, 2005; Thomas & Harden, 2008 ).

One of the most highly cited scoping reviews in the eHealth domain was published by Archer, Fevrier-Thomas, Lokker, McKibbon, and Straus (2011) . These authors reviewed the existing literature on personal health record ( phr ) systems including design, functionality, implementation, applications, outcomes, and benefits. Seven databases were searched from 1985 to March 2010. Several search terms relating to phr s were used during this process. Two authors independently screened titles and abstracts to determine inclusion status. A second screen of full-text articles, again by two independent members of the research team, ensured that the studies described phr s. All in all, 130 articles met the criteria and their data were extracted manually into a database. The authors concluded that although there is a large amount of survey, observational, cohort/panel, and anecdotal evidence of phr benefits and satisfaction for patients, more research is needed to evaluate the results of phr implementations. Their in-depth analysis of the literature signalled that there is little solid evidence from randomized controlled trials or other studies through the use of phr s. Hence, they suggested that more research is needed that addresses the current lack of understanding of optimal functionality and usability of these systems, and how they can play a beneficial role in supporting patient self-management ( Archer et al., 2011 ).

9.3.4. Forms of Aggregative Reviews

Healthcare providers, practitioners, and policy-makers are nowadays overwhelmed with large volumes of information, including research-based evidence from numerous clinical trials and evaluation studies, assessing the effectiveness of health information technologies and interventions ( Ammenwerth & de Keizer, 2004 ; Deshazo et al., 2009 ). It is unrealistic to expect that all these disparate actors will have the time, skills, and necessary resources to identify the available evidence in the area of their expertise and consider it when making decisions. Systematic reviews that involve the rigorous application of scientific strategies aimed at limiting subjectivity and bias (i.e., systematic and random errors) can respond to this challenge.

Systematic reviews attempt to aggregate, appraise, and synthesize in a single source all empirical evidence that meet a set of previously specified eligibility criteria in order to answer a clearly formulated and often narrow research question on a particular topic of interest to support evidence-based practice ( Liberati et al., 2009 ). They adhere closely to explicit scientific principles ( Liberati et al., 2009 ) and rigorous methodological guidelines (Higgins & Green, 2008) aimed at reducing random and systematic errors that can lead to deviations from the truth in results or inferences. The use of explicit methods allows systematic reviews to aggregate a large body of research evidence, assess whether effects or relationships are in the same direction and of the same general magnitude, explain possible inconsistencies between study results, and determine the strength of the overall evidence for every outcome of interest based on the quality of included studies and the general consistency among them ( Cook, Mulrow, & Haynes, 1997 ). The main procedures of a systematic review involve:

• Formulating a review question and developing a search strategy based on explicit inclusion criteria for the identification of eligible studies (usually described in the context of a detailed review protocol).
• Searching for eligible studies using multiple databases and information sources, including grey literature sources, without any language restrictions.
• Selecting studies, extracting data, and assessing risk of bias in a duplicate manner using two independent reviewers to avoid random or systematic errors in the process.
• Analyzing data using quantitative or qualitative methods.
• Presenting results in summary of findings tables.
• Interpreting results and drawing conclusions.

Many systematic reviews, but not all, use statistical methods to combine the results of independent studies into a single quantitative estimate or summary effect size. Known as meta-analyses , these reviews use specific data extraction and statistical techniques (e.g., network, frequentist, or Bayesian meta-analyses) to calculate from each study by outcome of interest an effect size along with a confidence interval that reflects the degree of uncertainty behind the point estimate of effect ( Borenstein, Hedges, Higgins, & Rothstein, 2009 ; Deeks, Higgins, & Altman, 2008 ). Subsequently, they use fixed or random-effects analysis models to combine the results of the included studies, assess statistical heterogeneity, and calculate a weighted average of the effect estimates from the different studies, taking into account their sample sizes. The summary effect size is a value that reflects the average magnitude of the intervention effect for a particular outcome of interest or, more generally, the strength of a relationship between two variables across all studies included in the systematic review. By statistically combining data from multiple studies, meta-analyses can create more precise and reliable estimates of intervention effects than those derived from individual studies alone, when these are examined independently as discrete sources of information.

The review by Gurol-Urganci, de Jongh, Vodopivec-Jamsek, Atun, and Car (2013) on the effects of mobile phone messaging reminders for attendance at healthcare appointments is an illustrative example of a high-quality systematic review with meta-analysis. Missed appointments are a major cause of inefficiency in healthcare delivery with substantial monetary costs to health systems. These authors sought to assess whether mobile phone-based appointment reminders delivered through Short Message Service ( sms ) or Multimedia Messaging Service ( mms ) are effective in improving rates of patient attendance and reducing overall costs. To this end, they conducted a comprehensive search on multiple databases using highly sensitive search strategies without language or publication-type restrictions to identify all rct s that are eligible for inclusion. In order to minimize the risk of omitting eligible studies not captured by the original search, they supplemented all electronic searches with manual screening of trial registers and references contained in the included studies. Study selection, data extraction, and risk of bias assessments were performed inde­­pen­dently by two coders using standardized methods to ensure consistency and to eliminate potential errors. Findings from eight rct s involving 6,615 participants were pooled into meta-analyses to calculate the magnitude of effects that mobile text message reminders have on the rate of attendance at healthcare appointments compared to no reminders and phone call reminders.

Meta-analyses are regarded as powerful tools for deriving meaningful conclusions. However, there are situations in which it is neither reasonable nor appropriate to pool studies together using meta-analytic methods simply because there is extensive clinical heterogeneity between the included studies or variation in measurement tools, comparisons, or outcomes of interest. In these cases, systematic reviews can use qualitative synthesis methods such as vote counting, content analysis, classification schemes and tabulations, as an alternative approach to narratively synthesize the results of the independent studies included in the review. This form of review is known as qualitative systematic review.

A rigorous example of one such review in the eHealth domain is presented by Mickan, Atherton, Roberts, Heneghan, and Tilson (2014) on the use of handheld computers by healthcare professionals and their impact on access to information and clinical decision-making. In line with the methodological guide­lines for systematic reviews, these authors: (a) developed and registered with prospero ( www.crd.york.ac.uk/ prospero / ) an a priori review protocol; (b) conducted comprehensive searches for eligible studies using multiple databases and other supplementary strategies (e.g., forward searches); and (c) subsequently carried out study selection, data extraction, and risk of bias assessments in a duplicate manner to eliminate potential errors in the review process. Heterogeneity between the included studies in terms of reported outcomes and measures precluded the use of meta-analytic methods. To this end, the authors resorted to using narrative analysis and synthesis to describe the effectiveness of handheld computers on accessing information for clinical knowledge, adherence to safety and clinical quality guidelines, and diagnostic decision-making.

In recent years, the number of systematic reviews in the field of health informatics has increased considerably. Systematic reviews with discordant findings can cause great confusion and make it difficult for decision-makers to interpret the review-level evidence ( Moher, 2013 ). Therefore, there is a growing need for appraisal and synthesis of prior systematic reviews to ensure that decision-making is constantly informed by the best available accumulated evidence. Umbrella reviews , also known as overviews of systematic reviews, are tertiary types of evidence synthesis that aim to accomplish this; that is, they aim to compare and contrast findings from multiple systematic reviews and meta-analyses ( Becker & Oxman, 2008 ). Umbrella reviews generally adhere to the same principles and rigorous methodological guidelines used in systematic reviews. However, the unit of analysis in umbrella reviews is the systematic review rather than the primary study ( Becker & Oxman, 2008 ). Unlike systematic reviews that have a narrow focus of inquiry, umbrella reviews focus on broader research topics for which there are several potential interventions ( Smith, Devane, Begley, & Clarke, 2011 ). A recent umbrella review on the effects of home telemonitoring interventions for patients with heart failure critically appraised, compared, and synthesized evidence from 15 systematic reviews to investigate which types of home telemonitoring technologies and forms of interventions are more effective in reducing mortality and hospital admissions ( Kitsiou, Paré, & Jaana, 2015 ).

9.3.5. Realist Reviews

Realist reviews are theory-driven interpretative reviews developed to inform, enhance, or supplement conventional systematic reviews by making sense of heterogeneous evidence about complex interventions applied in diverse contexts in a way that informs policy decision-making ( Greenhalgh, Wong, Westhorp, & Pawson, 2011 ). They originated from criticisms of positivist systematic reviews which centre on their “simplistic” underlying assumptions ( Oates, 2011 ). As explained above, systematic reviews seek to identify causation. Such logic is appropriate for fields like medicine and education where findings of randomized controlled trials can be aggregated to see whether a new treatment or intervention does improve outcomes. However, many argue that it is not possible to establish such direct causal links between interventions and outcomes in fields such as social policy, management, and information systems where for any intervention there is unlikely to be a regular or consistent outcome ( Oates, 2011 ; Pawson, 2006 ; Rousseau, Manning, & Denyer, 2008 ).

To circumvent these limitations, Pawson, Greenhalgh, Harvey, and Walshe (2005) have proposed a new approach for synthesizing knowledge that seeks to unpack the mechanism of how “complex interventions” work in particular contexts. The basic research question — what works? — which is usually associated with systematic reviews changes to: what is it about this intervention that works, for whom, in what circumstances, in what respects and why? Realist reviews have no particular preference for either quantitative or qualitative evidence. As a theory-building approach, a realist review usually starts by articulating likely underlying mechanisms and then scrutinizes available evidence to find out whether and where these mechanisms are applicable ( Shepperd et al., 2009 ). Primary studies found in the extant literature are viewed as case studies which can test and modify the initial theories ( Rousseau et al., 2008 ).

The main objective pursued in the realist review conducted by Otte-Trojel, de Bont, Rundall, and van de Klundert (2014) was to examine how patient portals contribute to health service delivery and patient outcomes. The specific goals were to investigate how outcomes are produced and, most importantly, how variations in outcomes can be explained. The research team started with an exploratory review of background documents and research studies to identify ways in which patient portals may contribute to health service delivery and patient outcomes. The authors identified six main ways which represent “educated guesses” to be tested against the data in the evaluation studies. These studies were identified through a formal and systematic search in four databases between 2003 and 2013. Two members of the research team selected the articles using a pre-established list of inclusion and exclusion criteria and following a two-step procedure. The authors then extracted data from the selected articles and created several tables, one for each outcome category. They organized information to bring forward those mechanisms where patient portals contribute to outcomes and the variation in outcomes across different contexts.

9.3.6. Critical Reviews

Lastly, critical reviews aim to provide a critical evaluation and interpretive analysis of existing literature on a particular topic of interest to reveal strengths, weaknesses, contradictions, controversies, inconsistencies, and/or other important issues with respect to theories, hypotheses, research methods or results ( Baumeister & Leary, 1997 ; Kirkevold, 1997 ). Unlike other review types, critical reviews attempt to take a reflective account of the research that has been done in a particular area of interest, and assess its credibility by using appraisal instruments or critical interpretive methods. In this way, critical reviews attempt to constructively inform other scholars about the weaknesses of prior research and strengthen knowledge development by giving focus and direction to studies for further improvement ( Kirkevold, 1997 ).

Kitsiou, Paré, and Jaana (2013) provide an example of a critical review that assessed the methodological quality of prior systematic reviews of home telemonitoring studies for chronic patients. The authors conducted a comprehensive search on multiple databases to identify eligible reviews and subsequently used a validated instrument to conduct an in-depth quality appraisal. Results indicate that the majority of systematic reviews in this particular area suffer from important methodological flaws and biases that impair their internal validity and limit their usefulness for clinical and decision-making purposes. To this end, they provide a number of recommendations to strengthen knowledge development towards improving the design and execution of future reviews on home telemonitoring.

9.4. Summary

Table 9.1 outlines the main types of literature reviews that were described in the previous sub-sections and summarizes the main characteristics that distinguish one review type from another. It also includes key references to methodological guidelines and useful sources that can be used by eHealth scholars and researchers for planning and developing reviews.

Typology of Literature Reviews (adapted from Paré et al., 2015).

As shown in Table 9.1 , each review type addresses different kinds of research questions or objectives, which subsequently define and dictate the methods and approaches that need to be used to achieve the overarching goal(s) of the review. For example, in the case of narrative reviews, there is greater flexibility in searching and synthesizing articles ( Green et al., 2006 ). Researchers are often relatively free to use a diversity of approaches to search, identify, and select relevant scientific articles, describe their operational characteristics, present how the individual studies fit together, and formulate conclusions. On the other hand, systematic reviews are characterized by their high level of systematicity, rigour, and use of explicit methods, based on an “a priori” review plan that aims to minimize bias in the analysis and synthesis process (Higgins & Green, 2008). Some reviews are exploratory in nature (e.g., scoping/mapping reviews), whereas others may be conducted to discover patterns (e.g., descriptive reviews) or involve a synthesis approach that may include the critical analysis of prior research ( Paré et al., 2015 ). Hence, in order to select the most appropriate type of review, it is critical to know before embarking on a review project, why the research synthesis is conducted and what type of methods are best aligned with the pursued goals.

9.5. Concluding Remarks

In light of the increased use of evidence-based practice and research generating stronger evidence ( Grady et al., 2011 ; Lyden et al., 2013 ), review articles have become essential tools for summarizing, synthesizing, integrating or critically appraising prior knowledge in the eHealth field. As mentioned earlier, when rigorously conducted review articles represent powerful information sources for eHealth scholars and practitioners looking for state-of-the-art evidence. The typology of literature reviews we used herein will allow eHealth researchers, graduate students and practitioners to gain a better understanding of the similarities and differences between review types.

We must stress that this classification scheme does not privilege any specific type of review as being of higher quality than another ( Paré et al., 2015 ). As explained above, each type of review has its own strengths and limitations. Having said that, we realize that the methodological rigour of any review — be it qualitative, quantitative or mixed — is a critical aspect that should be considered seriously by prospective authors. In the present context, the notion of rigour refers to the reliability and validity of the review process described in section 9.2. For one thing, reliability is related to the reproducibility of the review process and steps, which is facilitated by a comprehensive documentation of the literature search process, extraction, coding and analysis performed in the review. Whether the search is comprehensive or not, whether it involves a methodical approach for data extraction and synthesis or not, it is important that the review documents in an explicit and transparent manner the steps and approach that were used in the process of its development. Next, validity characterizes the degree to which the review process was conducted appropriately. It goes beyond documentation and reflects decisions related to the selection of the sources, the search terms used, the period of time covered, the articles selected in the search, and the application of backward and forward searches ( vom Brocke et al., 2009 ). In short, the rigour of any review article is reflected by the explicitness of its methods (i.e., transparency) and the soundness of the approach used. We refer those interested in the concepts of rigour and quality to the work of Templier and Paré (2015) which offers a detailed set of methodological guidelines for conducting and evaluating various types of review articles.

To conclude, our main objective in this chapter was to demystify the various types of literature reviews that are central to the continuous development of the eHealth field. It is our hope that our descriptive account will serve as a valuable source for those conducting, evaluating or using reviews in this important and growing domain.

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REVIEW article

Mental health among adolescents exposed to social inequality in latin america and the caribbean: a scoping review.

• 1 Institute of Health and Nursing Science, Charité – Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
• 2 Faculty of Nursing, Universidad El Bosque, Bogotá, Colombia
• 3 Faculty of Humanities, Social Science and Education, Otto-von-Guericke-Universität Magdeburg, Magdeburg, Germany

Background and objective: Adolescents from Latin America and the Caribbean grow up in a context of social inequality, which diminishes their well-being and leads to impaired emotional-cognitive development. To understand the problem, it is important to synthesize the available research about it. This study aims to explore the knowledge about adolescents’ mental health in Latin America and the Caribbean exposed to social inequality.

Methods: A systematic scoping review was conducted encompassing a search in five databases (Medline, CINAHL, PsycINFO, Scopus, and LILACS) in June 2022. Articles of various typologies were included without time limit. After two rounds of screening, relevant data were manually extracted and synthesized into self-constructed themes using thematic analysis.

Results: Out of 8,825 retrieved records, 42 papers were included in the final review, with a predominance of quantitative approaches. The synthesis revealed two main analytical themes: (a) defining social inequality, wherein intersecting inequalities produce discrimination and determine conditions for social vulnerability; (b) social inequality and mental health, which highlights the association between socio-structural difficulties and emotional problems, amplifying vulnerability to mental ill health and poor mental health care.

Conclusion: The scientific evidence reveals that social inequality is related to impaired well-being and mental ill health on the one hand and a lack of access to mental health care on the other hand.

1 Introduction

Adolescents have different roles in society: on the one hand, they represent the development of countries as they will be the adults of tomorrow, so they are the workforce of the future and the caregivers of generations to come ( 1 , 2 ). On the other hand, adolescence is portrayed as one of the most stressful phases in life ( 3 , 4 ) because it is connected to many challenges, such as hormonal and physical changes ( 5 , 6 ). In addition, the desire for independence, the establishment of an own identity, and/or the development of autonomy are also characteristics of this phase ( 6 , 7 ).

In the construction of their different roles, adolescents are particularly sensitive to the social, economic, and cultural environment in which they grow up ( 8 ). Scientific evidence shows that the socioeconomic background of their countries affects adolescents’ life satisfaction and quality of life ( 9 ). As a result of an environment marked by poverty and discrimination, youths experience insecurity and hopelessness as well as the feeling of not having the necessary resources to fulfill their life projects ( 4 , 10 , 11 ). This social vulnerability, combined with the chaotic phase of adolescence, creates mental stress scenarios, and in this process, serious mental health problems may emerge ( 10 , 12 ).

There is extensive evidence in the literature about how different aspects of social inequality are linked to mental health problems in adolescents. Studies conducted in Germany and Australia demonstrate that children and adolescents with low socioeconomic status (SES) and family difficulties have a higher risk of mental health problems ( 13 , 14 ). Another study shows that adolescents in South Africa living in poverty face stressful situations that often lead to symptoms of depression and anxiety ( 15 ). In research involving Chinese adolescents, it was found that those with advantageous socioeconomic conditions such as social support and adequate financial resources show a better mental health status than less privileged adolescents ( 16 ).

In Latin America and the Caribbean, adolescents grow up in a context of social inequality, which affects people’s lives in different ways. One type of social inequality is economic inequality, which includes income and property ( 17 , 18 ). Other forms of structural inequality hinder the fulfillment of human rights, the development of skills, educational and job-related opportunities, and autonomy ( 17 , 18 ). Contexts marked by structural inequality – characterized by low income, unemployment, social exclusion as well as poor access to health services, education, and housing – undermine the quality of life and lead to discontent among the most vulnerable populations ( 17 , 19 ). Especially among young people, inequality diminishes the possibilities to participate in society and to manage the transition to adulthood successfully, i.e., reaching their full potential and ultimately contributing to the improvement of society ( 1 , 20 ). Thereby, social inequality allows for the violation of adolescents’ rights, especially in families with low SES ( 21 ).

So far, research on the association between social inequality and adolescents’ mental health has primarily focused on high-income countries ( 22 , 23 ). Despite Latin America and the Caribbean being recognized as the region with the highest levels of inequality worldwide ( 24 , 25 ), only one literature review has examined the association between socioeconomic inequality and mental disorders, covering the general population, including adults ( 26 ). This highlights a clear gap in the synthesis of the relationship between social inequality and mental health in adolescents from Latin America and the Caribbean.

Therefore, the present study aims to explore the available knowledge about the mental health of adolescents exposed to social inequality in Latin America and the Caribbean. It also aims at identifying the definitions of social inequality used in literature available on the topic. As a guide for reporting the results of this study, we used PRISMA Extension for Scoping Reviews (PRISMA-ScR) ( 27 ).

Due to the complexity and heterogeneity of the research topic and to account for the conceptual aim of this research, it was considered optimal to conduct a scoping review ( 28 ). We followed the six-stage scoping review framework proposed by the Joanna Briggs Institute (JBI) ( 28 ), which consists of the following stages: (1) identifying the research questions; (2) identifying potentially relevant studies; (3) study selection; (4) data extraction; (5) analysis of evidence; (6) presentation of the results. The detailed protocol of this study is available online ( 29 ).

2.1 Search strategy

The search structure was designed based on the PEO strategy (Population, Exposure, Outcome) ( 30 ). The population of interest is defined as adolescents born and living in Latin America and the Caribbean. Social inequality, serving as exposure, is defined as social difference in living conditions and essential services among different social groups, encompasses social exclusion, discrimination, power imbalances, migration or forced displacement, poverty, and violence ( 31 ). The outcome is the adolescents’ mental health, defined as the individual’s sense of well-being, self-efficacy, autonomy, and competence, along with the development of social relationships ( 32 , 33 ).

The databases and keywords were determined with the support of an expert in Information Literacy Education/Systematic Reviews. We carried out searches in Medline (via OVID), CINAHL, PsycINFO, Scopus, and LILACS for articles resulting from primary research studies, systematic reviews, and reflection articles, including expert opinions on the subject in English, Spanish, and Portuguese. We did not limit our search by publication date. The search strings were adapted for the respective databases, but remained comparable. As an example, the full electronic search strategy for Medline is available in Appendix 1 .

The following criteria were applied in selecting the literature included: 1. The aim of the study refers to adolescence, which extends from 10 to 19 years of age ( 34 ). However, we include samples exceeding this range as well as adult samples as long as the purpose of the study clearly relates to the situation of adolescents. 2. The study focuses on a population born and living in Latin America or the Caribbean. 3. The study explains or analyses the association of social inequality with adolescents’ mental health.

2.2 Study selection

All databases were searched on 30 June 2022. Afterwards, all records were imported into Endnote X9.3.3 (Clarivate Analytics) to find and eliminate duplicates. Subsequently, all remaining literature was uploaded to the online systematic review platform Rayyan Systems, Inc. for further screening, first title and abstract, then full-text. We employed a team approach in this stage: due to linguistic competence, two of the researchers screened the results in English and Spanish (JCSC and LPG) and two in Portuguese (SEAM and VAMB). Discrepancies between the reviewers were reconciled through direct discussion at each phase until consensus was achieved.

Further sources were identified through a backward literature search by reviewing the references cited in the articles included ( 28 ). The main researcher (JCSC) checked the additional titles for inclusion criteria, and those eligible were included in the data extraction and analysis phase. A team approach was not used for the screening of these articles as they came from papers already included in the review, which represented an indirect screening. In addition, previous discussions provided experience for single-author decision making at this stage.

2.3 Data extraction and analysis

Information from the included records was extracted into a charting table in Microsoft Excel by JCSC. The following data were extracted: author, year, country, type of article, aim, design, study population, method/data, assessed variables, limitations/bias, and key findings regarding the conceptualization of social inequality, mental health approach, and associations between social inequality and mental health in adolescents in Latin America and the Caribbean. Subsequently, the information in the charting table was summarized alongside the general information of the studies.

For the qualitative synthesis, a process of inductive thematic construction for scoping reviews was used, consisting of manually identifying and classifying relevant and recurring patterns in the extracted text segments. These patterns were then reorganized into themes, with descriptive sub-themes when necessary, by which we answer our research questions ( 35 ).

3.1 Scope, nature, and distribution of literature

Figure 1 depicts the selection process ( 27 , 36 ). The initial database search yielded 8,825 articles. After elimination of duplicates, 5,077 studies remained. The title and abstract screening resulted in 106 articles. A total of 101 articles was retrieved as full text, the respective screening resulted in the final count of 39 articles. Another three publications were added by manually scanning the references of the included publications. In the end, a total of 42 articles met the inclusion criteria.

Figure 1 . Flow diagram of selection process (designed on miro.com ).

Supplementary Table S2 provides the characteristics of the 42 articles included. The articles were published between 1989 and 2022. When classifying the year of publication by decades, a greater number of publications was found in the period from 2011 to 2020 ( n  = 23). The majority of studies were conducted in Brazil ( n  = 19), with the remaining articles written by authors in Colombia ( n  = 5), Mexico ( n  = 5), Chile ( n  = 4), Ecuador ( n  = 4), Nicaragua ( n  = 2), Peru ( n  = 2), and one study included two countries, Colombia and Mexico. The predominant language was English ( n  = 28), followed by Spanish ( n  = 8) and Portuguese ( n  = 6). We identified 39 original articles, one letter to the editor, one description of the implementation of a health care project, and one review of the scientific literature. Among the original articles, most used a quantitative design ( n  = 29), 27 were cross-sectional studies, one cohort study, and one panel study. A total of eight studies were conducted qualitatively, and two followed a mixed methods design.

3.2 Thematic findings

As a result of the thematic analysis, two main themes emerged: 1. Defining social inequality; 2. Social inequality and mental health. For the second theme, the construction of sub-themes “social inequality threatening well-being,” “social inequality and mental ill health,” and “mental health care in social inequality environments” was significant to deepen its description.

3.2.1 Theme 1: Defining social inequality

Across the 42 studies included, we identified varied approaches in defining social inequality. The concepts mapped in this theme are presented in Figure 2 . Social inequality seems to emerge from the interplay of ethnicity/race, migration, gender, and class. These are social categories that play a decisive role in shaping the social environment.

Figure 2 . Theme 1: Defining social inequality (designed on miro.com ).

Regarding ethnicity/race, it is described how populations with ethnic-racial background often experienced inequitable treatment ( 37 , 38 ). One of the articles reports people being mostly white in the central areas of the cities, where socioeconomic conditions were favorable (better parental education and formal employment) ( 39 ). However, in populations of African descendants, lower levels of structured education and low income were prominent ( 40 ).

Another relevant phenomenon was migration due to various reasons, e.g., forced migration related to conflict and war, rural–urban migration, international migration that might be south–south among Latin American and Caribbean countries (between countries or regions located in the global South, involves people moving from one developing country to another) or south–north (from less economically developed regions to more economically developed countries) ( 41 – 45 ). Migrant population usually concentrated in the peripheral neighborhoods embodied by social vulnerability ( 42 , 45 ).

Few studies investigated the role of gender in perpetuating social inequality. This research sheds light on traditional patriarchal norms (sometimes based on religious belief), exposing women to greater social and financial vulnerability ( 46 , 47 ). When gender inequalities were conjoined with socioeconomic stratification (class), compelling evidence of social inequality emerged. For instance, among groups of economically disadvantaged adolescents who were obliged to work, female adolescents were usually engaged in unpaid activities such as stay-at-home care for younger siblings and household chores, while male adolescents were engaged in paid work ( 46 , 47 ).

In several studies, the concept of SES was used to classify the participants according to their class, for example, based on goods and assets of the family, and/or schooling of the head of the household ( 37 , 45 , 48 – 56 ). The type of school such as municipal or subsidized school and paid school was also used to define the SES ( 57 ). In these papers, this classification was based on the location of the schools or households like low-, middle-, or high-income areas ( 58 , 59 ).

In social environments where ethnicity/race, migration, gender, and/or class intersecting inequalities emerge, the affected population became marginalized, facing exclusion from state provisions and broader societal engagement ( 50 , 60 , 61 ). Notably, impoverished adolescents were distinctively affected by discrimination, social exclusion, and impediments in the realization of fundamental human rights ( 37 , 61 – 65 ).

Furthermore, individuals facing intersecting inequalities were susceptible to social vulnerability, which manifests through challenging life circumstances ( 20 , 40 , 46 , 60 , 62 , 64 – 70 ). Several articles highlight poverty as one of the most significant determinants of social vulnerability. Poverty has been widely associated with income shortfall. More recently, this concept has been expanded to the consumption of goods and services ( 71 ). However, the essential definition of poverty recognizes it as a fundamental life condition that affects social, economic, and environmental relations and determines the degree of social inequality ( 20 , 39 , 40 , 47 , 54 , 57 – 59 , 61 , 62 , 65 , 68 , 71 – 74 ).

Moreover, a number of studies have reported that poor infrastructure is characteristic for social vulnerability. Two studies point out that neighborhoods dominated by low social status presented hazardous life circumstances which included residences in a precarious state of repair and with insufficient rooms and thus hindering privacy, lack of piped water, sewage, and electricity as well as inadequate garbage collection ( 68 , 75 ). Poor infrastructure is also related to lack of public transportation, besides leisure, education and health centers ( 39 , 47 , 58 ). Furthermore, in 11 articles, disadvantaged neighborhoods were characterized by high levels of insecurity (violence and accidents), drug trafficking, urban crime, police raids, assaults, robberies, and shootouts ( 20 , 39 , 42 , 58 , 59 , 62 , 63 , 65 , 67 , 70 , 76 ).

Social vulnerability was further manifested in the disparities in educational attainment among individuals from low, middle, and higher socioeconomic classes ( 39 ). The access to education among poor adolescents is erratic, reflected in their low school enrolment ( 20 , 42 , 46 , 62 , 65 , 70 , 71 ). This phenomenon also occurs in the parental (household head) generation among disadvantaged groups ( 40 , 58 , 66 ).

Similarly, numerous studies reported that caregivers’ loss of employment or engagement in low-status occupations, particularly within informal, illegal, or low-paying sectors, contributed to an increase in the family’s social vulnerability ( 20 , 39 , 40 , 42 , 58 , 66 , 70 , 72 ). Furthermore, the need of increasing family income could push young individuals into premature employment, which could be harmful because it interferes with their education and personal development ( 46 , 65 , 76 ). Unemployment and economic risk lead to food insecurity and insufficiency and thus, to adolescents suffering from hunger ( 20 , 43 , 58 ).

Social vulnerability is also reflected in family issues. Three author teams identified family disruption as an indicator of socioeconomic disadvantage ( 40 , 47 , 67 ). Across 11 articles, social vulnerability within the family setting is described through various factors, including parental conflict and divorce, the presence of a stepfather, extended family or single-parent family, or mother-only households ( 39 , 40 , 42 , 47 , 58 , 66 ). Two-parent families were expected to provide much more stability, with changes in the family structure considered as a risk factor ( 39 , 58 ). Fragile families are also characterized by domestic violence and familial addiction ( 62 , 63 ). In Latin America and the Caribbean, the breakdown of the family structure is common due to international migration, when adults leave their country of origin in search of employment and resources, leaving their children behind in the care of grandparents or other relatives ( 41 , 44 ).

3.2.2 Theme 2: Social inequality and mental health

Across various studies, there was evidence that social inequality was negatively related to adolescents’ mental health. The concepts mapped in this theme are presented in Figure 3 . Sub-themes were 1. Social inequality threatening well-being: how social inequality is related to the positive mental health approach, emphasizing concepts like well-being and quality of life. 2. Social inequality and mental ill health: focusing on a clinical standpoint, analyzing symptoms and/or mental health disorders that are prevalent among adolescents experiencing social inequalities. 3. Mental health care in social inequality environments: the lack of access to mental health care for adolescents facing social inequality.

Figure 3 . Theme 2: Social inequality and mental health (designed on miro.com ).

3.2.2.1 Social inequality threatening well-being

A number of studies reported that well-being was a key component of mental health and was based on the degree that each individual assesses their life circumstances, depending on the possibility to cope with and assimilate life events ( 49 , 59 , 65 ). There are three types of well-being: subjective well-being, psychological or eudaemonic well-being, and social well-being ( 70 ). Here, we map the diverse ways in which social inequality poses challenges to overall well-being, encompassing the intricate interplay between the abovementioned types.

Some evidence showed that the higher the social inequality, the lower the well-being ( 49 , 59 , 65 , 71 , 73 ). We found research on how intersecting inequality relates to mental health. Two studies described how discrimination based on ethnicity/race generates negative emotional responses, thereby raising difficulties for the proper development of mental health ( 37 , 38 ). In particular, two papers reported how adolescents who were left behind after their parents’ migration reported feelings of sadness, loneliness, and behavioral problems ( 41 , 44 ). Moreover, patriarchal norms affected the communication and expression of feelings among female adolescents, especially in relation to sexuality, creating feelings of inferiority in young women ( 47 ). In this regard, a synergy could be seen between gender and SES, with women from schools in poorer social conditions having less self-esteem and stronger feelings of anxiety and sadness ( 57 ). In addition, adolescents’ quality of life was reduced by high levels of emotional stress resulting from the lack of social and economic resources, representing early adversity for youths ( 42 , 52 , 53 , 55 , 56 , 59 , 65 , 71 , 74 ). The result was social vulnerability characterized by stressful events and lower levels of positive emotionality ( 40 , 53 , 58 , 74 ). Social vulnerability was associated with aggressive behavior ( 20 , 65 , 67 ) with the affected adolescents becoming victims or aggressors, perpetuating the vicious circle of violence ( 59 ).

Furthermore, increased poverty and perceived social exclusion were associated with lower self-esteem, perception of having less social support, and feelings of isolation and intimidation ( 37 , 38 , 58 , 65 ) as well as feelings of unfairness, frustration, disrespect, anger, and hopelessness ( 42 , 59 , 69 ). In general, lack of opportunities and sometimes also of information hindered adolescents to follow their life projects and aspirations for a better future (better conditions than those of their caregivers) ( 65 , 68 , 71 ).

Besides, well-being was constantly threatened in hostile environments characterized by high levels of insecurity, violence, and crime as well as precarious infrastructure such as substandard housing, inadequate sanitation, and low quality of local services ( 48 , 65 , 67 , 72 , 77 ). Having computer or internet access was essential to perform academic activities, but not available to disadvantaged adolescents, leading to daily stress ( 50 ).

Socially vulnerable families were more likely characterized by family conflicts and tensions, intra-familiar violence, illnesses, single-parent families, large families, and unemployment, which were considered as stressful situations impairing adolescents’ mental health and quality of life ( 50 , 54 , 56 , 63 , 67 ). Likewise, low levels of parental education and little or no paid work might impose stress and reduce the mental stability of adolescents ( 49 , 65 , 77 ).

These life circumstances played a central role in adolescents’ academic performance as well: in schools where students had better socioeconomic conditions, their cognitive and psychosocial skills were better developed than in schools located in poor areas, generally public schools ( 60 , 65 ). Although one study reported that educational work with adolescents could help them improve their self-esteem as they felt valuable to their family and community ( 76 ), this was different when measured in relation with other work circumstances. For instance, adolescents who could not study because they have to work or those not in education, employment, or training (NEET) are affected by social vulnerability that puts their mental health at risk since they are unable to meet social expectations, and this generates feelings of dissatisfaction with life ( 66 ). In addition, when economic difficulties force the youngest members of the family to work, they suffer from the responsibility to provide for a family far too early ( 46 ).

The situation of street adolescents was complicated in its own way, since most of them fled from the negative situation at home, thinking that in the street they would find autonomy and freedom to fulfill their life expectations ( 61 ). However, they ended up facing the sense of having lost family protection, resulting in feelings of shame and loss, exclusion, discrimination, and violence ( 61 ). In addition, they tended to develop inappropriate behaviors such as taciturnity, hostility, and mistrust ( 63 ).

3.2.2.2 Social inequality and mental Ill health

Mental health was often investigated from a psychopathological perspective. The common terms used were “mental ill health,” “common mental disorders” or “psychiatric disorders” in the literature in English and its equivalent translation in the other two languages ( 39 , 42 , 52 , 64 , 69 , 71 ). Here, we present different associations found between social inequality and mental health problems.

Several studies reported that socioeconomic adversities were associated with mental ill health ( 40 , 42 , 69 , 74 , 75 ). Less formal education and parental unemployment were found as strong predictors of high rates of mental disorders ( 40 , 50 , 71 , 72 , 74 ). While one group of researchers identified that a significant portion of depressed adolescents were associated with functional families ( 54 ), in most studies, disruptions in the family structure played an important role in the vulnerability of internalizing and externalizing problems ( 40 , 43 , 50 , 71 , 72 ). Although in one of the studies, no significant difference between inner city and outer city areas was found ( 39 ), living in structurally deprived neighborhoods or in under-served rural areas was shown to be associated with psychosocial deprivation and thus, with the vulnerability to develop mental illness in two other papers ( 72 , 74 ). Research in adolescents identified as NEET showed that they have greater odds of mental ill health in connection with disengagement from social, educational and working life ( 66 ).

Poverty and social vulnerability were associated with depressive and anxiety symptoms ( 20 , 40 , 51 , 64 ). This was the case in the children of ragpickers who reported how the constant presence of garbage in their homes caused a feeling of constant discomfort with their environment ( 72 ). Furthermore, young people who experienced racial discrimination showed higher rates of depression compared to those who never felt discriminated ( 37 ). Working adolescents showed higher levels of anxiety or depressive symptoms than those who did not ( 46 ). Food insecurity and hunger were also associated with depressive symptoms in adolescents ( 43 ).

Further important mental health issues among poor adolescents were social problems, aggressive behavior, and antisocial behavior (ASB) ( 20 , 40 , 51 , 67 ). In most cases, male adolescents were more likely to externalize their problems ( 39 ). Family conflict, in particular when parents used physical punishment as disciplinary strategies, confers risk for aggressive behavior and other externalizing disorders ( 40 , 67 ). In addition to the psychiatric diagnoses mentioned above, it is important to remark the high probability of developing post-traumatic stress disorder (PTSD) in street adolescents who experienced extreme inequality and thus, vulnerability ( 62 ).

Some studies reported how the effects of social vulnerability described above can also trigger suicidal behavior ( 47 , 56 , 58 , 72 ). Being a child of a ragpicker, racial discrimination, hunger, and low parental/guardian involvement are risk factors for self-injury ( 37 , 43 , 72 ). In addition, the absence of social support networks can be a risk factor for suicidal behavior ( 56 , 66 ). One research on the socioeconomic and political determinants of suicide in adolescent females showed an association of turbulent political situations, traditional patriarchal norms, and the weakening of religions with suicidal behavior ( 47 ).

3.2.2.3 Mental health care In social inequality environments

Few studies investigated how families, health system, society and governments recognize and attend to adolescents’ mental health. Two studies reported that sometimes mental health issues were denied, e.g., by parents who reported that their children’s complaints were somatic in nature ( 20 , 75 ). Furthermore, mental health care was shown to often be lacking in poor areas ( 40 , 57 , 65 , 71 ). Likewise, lower income populations with higher morbidity received less than the minimum amount of mental health care, while privileged populations received excessive assistance – this is known as “inverse care law” ( 40 , 48 , 56 , 57 ).

Finally, it was reported that improving adolescents’ mental health required major efforts at different levels. First of all, structural and systematic interventions were needed to address inequality and social vulnerability ( 44 , 52 ). At the same level, it was necessary to promote dignified and well-paid employment for caregivers as well as strategies to increase family cohesion ( 40 , 44 , 65 , 67 ). The development of social support networks in which adolescents and their families can trust was highly recommended ( 42 , 45 , 65 , 70 ). For instance, the construction of youth organizations that motivate them to optimize the utilization of leisure time and achieve social inclusion removing discrimination of all kinds ( 37 , 42 , 44 , 45 , 70 ).

4 Discussion

In this scoping review, we described the concept of social inequality based on intersecting inequalities and social vulnerability of adolescents as well as the resulting life circumstances in Latin America and the Caribbean. Furthermore, this scoping review shows that social inequality in different countries is associated with negative emotions related to the low well-being of adolescents, harms their self-esteem, hampers the life projects viability, and fosters feelings of isolation. It is also revealed that these contexts are related to the presence of mental illness and suicidal behavior. In addition, we highlight the lack of access to health promotion, prevention, and care services in mental health for young people experiencing social vulnerability.

4.1 Defining social inequality

Through the thematic analysis of the articles included in this review, we examined the broad and complex concept of social inequality, revealing how important it is for Latin American and Caribbean societies, since this is considered to be a region with highest rates of inequalities compared with other areas in the world ( 24 , 25 , 67 ). The unequal conditions in which people in the region live have caused social injustice and difficulties for the population to have opportunities maintaining their quality of life and achieving individual and collective well-being ( 78 ).

To understand the complexity of the concept of social inequality, we consider the approach of intersectionality, which has been used in previous research to analyze social inequality in Latin America, for example by Baquero Melo ( 79 ). This analytical framework acknowledges the diversity inherent in human experiences by contemplating the overlapped dimensions of ethnicity/race, migration, gender, and class ( 79 ). In this approach, it is recognized that these categories are inseparable ( 31 ). Previous studies have reported that adolescents in Latin America growing up in a context that presents them obstacles to different levels, resulting in the accumulation and reinforcement of inequality ( 79 , 80 ).

Social inequality is also closely linked to discrimination, with certain populations experiencing unfair and unfavorable treatment based on characteristics such as low SES, ethnicity/race, migrant background, or gender identity (Erin ( 81 , 82 )). In Latin America and the Caribbean, research indicates that disadvantaged communities encounter limited access to opportunities and resources due to the prejudices and stigmatization present in society. This means that social inequality and discrimination creates a self-reinforcing cycle that hinders the comprehensive human development of these marginalized populations ( 17 , 80 , 81 ). In this way, a profound acknowledgment arises concerning the intensified infringement upon the fundamental rights of certain groups ( 25 , 83 ).

We raise a warning regarding unfavorable life circumstances specifically concerning poverty, poor infrastructure, violence and crime, limited educational opportunities, unemployment, food insecurity, and family issues. These factors have been found to have detrimental associations with adolescents’ mental health ( 84 ). Furthermore, given the lack of evidence in rural areas in this scoping review, future primary studies should focus on examining social inequality in these regions. It is essential to consider the challenges posed by limited access to healthcare, education, and other vital services in rural territories. By addressing these issues, we can gain valuable insights into social disparities and develop targeted interventions to tackle these challenges effectively. This realization poses a significant challenge in developing effective public policies and attention programs addressing the needs of the most vulnerable populations. The aim is to dismantle the underlying structures of social inequality and thus, to ensure equitable access to human rights and better living conditions for all ( 17 ).

It is acknowledged that consolidating all countries in the region into a single study of social inequality may oversimplify matters, considering the distinct historical, social, political, and cultural processes unique to each nation. However, gaining a general overview of the situation remains valuable, as it aids in understanding the regional profile and furnishes the essential knowledge needed for formulating comprehensive public policies. Moreover, it presents an opportunity to advance research by exploring the specific characteristics of each country in future studies.

4.2 Social inequality and mental health

The associations outlined herein are contextualized within Latin America and the Caribbean, where historical processes of colonization contribute to racial hierarchies, discrimination, and the marginalization of diverse ethnic groups ( 85 ). Furthermore, traditional gender roles prevail, with men often being the authoritarian heads of households, while women are relegated to secondary positions ( 86 ). Additionally, economic and political shifts, frequently accompanied by violence and criminality, have shaped the socio-economic situation of whole peoples and, in many cases, have driven migration both within and beyond national borders ( 87 ). It is therefore essential to comprehend mental health as an experience influenced by all the social phenomena inherent to the region. From this perspective, we can identify processes aimed at enhancing the living conditions and health of adolescents residing in the area ( 88 ).

In this scoping review, three distinctive sub-themes regarding the association between social inequality and mental health have emerged, delineated based on the various aspects examined in the included studies. The first sub-theme is based on the well-being and positive mental health approach, studies from this perspective refer to mental health in terms of quality of life, life satisfaction, and social relationships, explaining that mental health goes beyond diagnosing illnesses and requires attention based on health promotion and psychosocial work ( 89 ).

Well-being appeared as the prevailing concept frequently employed to define positive mental health within the scope of the included articles. Moreover, we found diverse well-being dimensions that contribute to a more nuanced understanding of the relationship between social inequality and mental health. First, subjective well-being was most commonly used by researchers and has two essential components: (a) the affective or emotional component which includes a balance between positive and negative affectivity or emotional responses and (b) the cognitive component characterized by the evaluation of global satisfaction with life ( 48 , 57 , 59 , 73 , 76 ). This scoping review highlights a consistent pattern indicating that adolescents residing in contexts characterized by social inequality present diminished levels of subjective well-being. To assess this phenomenon various instruments were used, encompassing evaluations of quality of life, self-esteem, and life satisfaction. The evidence indicates that social vulnerability serves as a potent stressor, fundamentally linked to the experience of reduced positive emotionality and self-esteem among adolescents not only in Latin America and the Caribbean but other social inequality contexts around the world ( 4 , 90 ).

The second dimension is psychological or eudaemonic well-being. Adolescents facing conditions of poverty, poor infrastructure, limited educational opportunities, and unemployment confront significant challenges in fostering hope for the future and realizing their personal aspirations ( 68 , 70 ). This is comparable to adolescents from other regions in the world. For example, a study among adolescents from families with financial difficulties in China found that adolescents’ future orientation is under threat ( 91 ). The results of this scoping review in a Latin American context supported it. In the included literature there is evidence on how the scarcity of socioeconomic resources and the adversities stemming from the intersecting inequalities of ethnicity/race, migration, gender, and class can impede the adolescents’ autonomy and freedom of choice concerning life goals or finding their own way for investing an effort ( 61 , 70 ).

Thirdly, social well-being refers to the capacity to be part of society and to build social networks ( 70 ). The institutions of family, community, school, the state, informal support networks, and the relationships formed between their members are a key component of well-being and the fulfillment of human needs ( 61 , 68 ). For adolescents, family is one of the most important protective factors for mental health through the dimensions of cohesion, affectivity, hierarchies or roles, communication, decision making, and conflict resolution ( 40 , 43 , 54 ). Family marks an important influence on the development of the individual’s personality ( 40 , 44 , 75 ). Consequently, households with adolescents experiencing family disintegration, domestic violence, economic hardships, and insufficient resources to fulfill fundamental nutritional and housing requirements pose a significant concern, not only for social well-being but also due to their connection with other dimensions of well-being. These adversities are closely linked to diminished levels of self-esteem, self-efficacy, and self-concept ( 92 ).

It is imperative to underscore the profound challenges faced by populations affected by intersectional discrimination. According to numerous research studies, these discriminatory experiences are strongly associated with negative feelings that significantly jeopardize mental well-being ( 38 , 93 , 94 ).

The second sub-theme was identified through an illness-centered approach, which concerns about manifestations of mental health disruptions, symptoms, and disorders ( 89 ). Numerous investigations have delved into mental health from a psychopathological standpoint. The terminologies employed in the included studies encompassed mental ill health, common mental disorders, or psychiatric disorders ( 39 , 42 , 52 , 64 , 69 , 71 ). We opted to label our sub-theme as mental ill health to cover comprehensive evidence concerning mental diagnostics and problematic behaviors. Moreover, the concept of internalizing and externalizing problems was also used. Internalizing problems comprises symptoms of anxiety and depression, i.e., those problems are directed toward oneself ( 40 , 46 , 74 ). Externalizing problems comprise breaking of rules, disruptive, delinquent, ASB, and/or aggressive behavior, mainly toward others ( 20 , 40 , 46 , 74 ).

The predominant mental disorders observed in adolescents are depression ( 43 , 51 , 53 , 57 ) and anxiety ( 57 , 66 , 74 ). Through this scoping review, we have established an association between social inequality and the prevalence of these mental illnesses among adolescents in Latin America. This association is grounded in the understanding that socioeconomic adversity and discrimination give rise to concerns and stressors that adversely compromise well-being, thereby acting as significant risk factors for the onset of these disorders ( 11 , 12 , 95 , 96 ).

The literature reviewed also found an association between social inequality and discrimination with ASB, a heterogeneous concept that encompasses behaviors as diverse as physical fighting, vandalism, stealing, status violation, and disobedience to adults. This association had also been considered by other authors, who reported that ASB in children and adolescents was associated with low SES ( 97 ).

Although not among the most prevalent mental health conditions in adolescents, this scoping review identified relevant information concerning the association between PTSD and social inequality experienced by street adolescents ( 62 ). PTSD appears when individuals or populations are exposed to highly distressing and traumatic events, such as violence or natural disasters, which jeopardize their physical and emotional well-being ( 98 ). Adolescents experiencing social inequality, characterized by highly unfavorable conditions, such as armed conflicts, extreme poverty, or gender-based violence, are at high risk for adverse mental health outcomes and the development of PTSD ( 98 – 100 ).

Finally, the included literature also assessed suicidal behavior among adolescents, which can be associated with psychological, especially affective, disorders ( 43 , 47 , 72 ) and comprises intentional self-harm, suicidal ideation (with or without planning), attempted suicide, and completed suicide ( 37 , 43 , 56 , 58 , 66 ). During adolescence, the influence of socioeconomic contexts can potentially contribute to inadequate emotional regulation and ineffective coping with stressful situations stemming from social inequality and discrimination. These factors may be associated with deliberate self-harm tendencies ( 96 ).

The third sub-theme that emerged from the thematic analysis refers to mental health care for populations facing social inequality. This aspect assumes crucial significance as it highlights how individuals in the most challenging life circumstances often confront scarcity of resources to effectively address their mental health ( 84 , 95 ). However, this sub-theme addressed the type of interventions that would improve the mental health of adolescents in Latin America and the Caribbean, which respond to the development of strategies that firstly address the underlying causes of social inequality, such as social programs and poverty reduction programs ( 92 , 101 ). Secondly, it is essential to build community spaces that seek to promote the well-being and quality of life of adolescents, with a focus on primary health care and mental health promotion ( 102 , 103 ).

5 Strengths and limitations

The scoping review approach was convenient in our study because the available scientific literature was extensive. Hence, through this methodology, it was possible to map the information and include various aspects needed to answer the research question and understand how social inequality is associated with mental health. The methodology employed, based on JBI guidelines ( 28 ), facilitated the systematic development of each of the six research steps and provided an overview of the available literature on the topic of interest. It is noteworthy that within this methodological framework, risk of bias assessment and critical appraisal are not mandatory, as the primary aim is not to critically synthesize the evidence. Consequently, this scoping review does not comprise critical appraisal. Instead, evaluation of the studies focused on their relevance to the research aim in accordance with the inclusion criteria outlined at the outset. Furthermore, two authors of this study (JCSC and SEAM) are trained by JBI in the development of scoping reviews. Although the main author (JSCS) only has knowledge of Spanish and English, the fact that two authors (SEAM and VAMB) are fluent in Portuguese made it possible to break down the language barrier and broaden the scope of the review. Another strength of the methodology was the involvement of an expert in Information Literacy Education/Systematic Reviews in the construction of the search strategy.

However, it is important to highlight the limitations of this review. Firstly, in formulating the search strategy, terms such as “ethnicity/race”, “migration”, and “gender”, along with closely related terms, were omitted. This decision was made because including these terms redirected the results to issues not within the scope of this review. Consequently, only broader terms such as “social segregation”, “social exclusion”, and “social discrimination”, among others, were included. So most of the available information on intersecting social inequality refers to socioeconomic stratification/class. Thus, it is considered relevant to recognize and expand knowledge about the influence of these three variables related to social inequality and adolescent mental health. While our search strategy includes research from a wide range of countries in the Latin America and the Caribbean ( n  = 42), the final review revealed that the reported research originated from only seven countries (Brazil, Chile, Colombia, Ecuador, Mexico, Nicaragua, and Peru), with none of them considered part of the Caribbean. This highlights the lack of research in the field of social inequality and adolescent’s mental health in the Caribbean region, potentially attributed to limited resources or the stigma surrounding mental health in the area ( 104 , 105 ). This study underscores the necessity for increased focus on primary research addressing this topic in Caribbean countries. The limited representation of countries may introduce potential bias and restrict the generalizability of our findings to other countries within the region.

The data extraction sheet was designed by one author (JCSC) and discussed among the team (SEAM, VAMB, and KH) before starting the extraction step. The data extraction process was carried out by only one author (JCSC). However, the information extracted from the Portuguese articles was verified by the fluent Portuguese authors (SEAM and VAMB). The thematic analysis was developed by one author (JCSC) and then discussed with three authors (LPG, SEAM, and VAMB) in order to arrive at the refined themes and sub-themes presented in this study. While relying on a single researcher for data extraction and thematic analysis facilitates focused exploration, it may limit diverse insights and overlook data nuances ( 106 ). Collaborative analysis involving multiple perspectives might have mitigated these limitations, fostering a more holistic and robust understanding of the data.

6 Conclusion

This scoping review represents an overview of the social inequality experienced by adolescents in Latin America and its relationship with mental health outcomes. Scientific literature establishes that social inequality operates at the intersection of ethnicity/race, migration, gender, and socioeconomic class. These dimensions, along with experiences of discrimination and social vulnerability, contribute to the perpetuation of inequality. This review reveals an association between social inequality and adverse mental health outcomes in adolescents. Adolescents exposed to intersecting inequalities reported low levels of well-being as well as higher levels of mental ill health and difficulties accessing mental health care.

In light of these compelling findings, we issue a resounding call to action to academia, government agencies, the private sector, and health systems across the region to develop strategic interventions that address the structural challenges of social inequality. By enhancing living conditions and improving the root causes threatening the well-being and mental health of young people, we can foster a more equitable and healthier adolescence.

Author contributions

JSCS: Conceptualization, Investigation, Formal Analysis, Writing – original draft, Writing – review & editing. LPG: Conceptualization, Investigation, Writing – original draft, Writing – review & editing. SEAM: Investigation, Writing – original draft, Writing – review & editing. VM-B: Investigation, Writing – review & editing. CS: Conceptualization, Writing – review & editing. KH: Conceptualization, Writing – original draft, Writing – review & editing.

The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.

Acknowledgments

We thank to Corinna Dressler, PhD; Medical Library Charité – Universitätsmedizin Berlin for her support and advice in the development of the search strategy. Support by the German Academic Exchange Service (DAAD, doctoral scholarship for JCSC) is gratefully acknowledged.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpubh.2024.1342361/full#supplementary-material

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Keywords: adolescents, mental health, psychological phenomena, social discrimination, social inequality, social sciences, social vulnerability, well-being

Citation: Sánchez-Castro JC, Pilz González L, Arias-Murcia SE, Mahecha-Bermeo VA, Stock C and Heinrichs K (2024) Mental health among adolescents exposed to social inequality in Latin America and the Caribbean: a scoping review. Front. Public Health . 12:1342361. doi: 10.3389/fpubh.2024.1342361

Received: 21 November 2023; Accepted: 19 March 2024; Published: 10 April 2024.

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Copyright © 2024 Sánchez-Castro, Pilz González, Arias-Murcia, Mahecha-Bermeo, Stock and Heinrichs. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Johanna Carolina Sánchez-Castro, [email protected]

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• Jithin Vishnu 1 ,
• Geetha Manivasagam   ORCID: orcid.org/0000-0003-3326-3176 1 ,
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Balloon expandable coronary stenting has revolutionized the field of interventional cardiology as a potential, minimally invasive modality for treating coronary artery disease. Even though stenting is successful compared to angioplasty (that leaves no stent in place), still there are many associated clinical complications. Bare metal stents are associated with in-stent restenosis caused mostly by neointimal hyperplasia, whereas success of drug-eluting stents comes at the expense of late-stent thrombosis and neoatherosclerosis. Even though innovative and promising, clinical trials with bioabsorbable stents reported thrombosis and a rapid pace of degradation without performing scaffolding action in several instances. It should be noted that a vast majority of these stents are based on a metallic platform which still holds the potential to mitigate major cardiovascular events and reduced economic burden to patients, alongside continuous improvement in stent technology and antiplatelet regimes. Hence, a systematic review was conducted following PRISMA guidelines to assess the clinically relevant material properties for a metallic stent material. From a materials perspective, the major causes identified for clinical failure of stents are inferior mechanical properties and blood-material interaction–related complications at the stent surface. In addition to these, the stent material should possess increased radiopacity for improved visibility and lower magnetic susceptibility values for artefact reduction. Moreover, the review provides an overview of future scope of percutaneous coronary interventional strategy. Most importantly, this review highlights the need for an interdisciplinary approach by clinicians, biomaterial scientists, and interventional cardiologists to collaborate in mitigating the impediments associated with cardiovascular stents for alleviating sufferings of millions of people worldwide.

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The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

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14 february 2022.

A Correction to this paper has been published: https://doi.org/10.1007/s44164-022-00010-3

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JV would like to acknowledge the funding received from Council of Scientific and Industrial Research (CSIR), India, under Direct-SRF scheme (Award No.: 09/844(0108)/2020-EMR-I).

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Jithin Vishnu, Geetha Manivasagam & K. G. Prashanth

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Diego Mantovani

Center for Energy Metabolism and Reproduction, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, Guangdong, China

Anjaneyulu Udduttula & Pei-Gen Ren

School of Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK

Anjaneyulu Udduttula

Biionix Cluster and College of Medicine, University of Central Florida, 6900 Lake Nona Blvd, Orlando, FL, 32827, USA

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Department of Mechanical Engineering, Colorado State University, Fort Collins, CO, 80523, USA

Ketul C. Popat

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Vishnu, J., Manivasagam, G., Mantovani, D. et al. Balloon expandable coronary stent materials: a systematic review focused on clinical success. In vitro models 1 , 151–175 (2022). https://doi.org/10.1007/s44164-022-00009-w

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Received : 05 October 2021

Revised : 11 January 2022

Accepted : 13 January 2022

Published : 31 January 2022

Issue Date : April 2022

DOI : https://doi.org/10.1007/s44164-022-00009-w

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