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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

  • An introductory paragraph that explains what your working topic and thesis is
  • A forecast of key topics or texts that will appear in the review
  • Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
  • 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 sentence to draw connections, comparisons, and contrasts.

Conclusion:

  • Summarize the key findings you have taken from the literature and emphasize their significance
  • Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

  • Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
  • Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
  • Qualitative versus quantitative research
  • Empirical versus theoretical scholarship
  • Divide the research by sociological, historical, or cultural sources
  • Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

  • It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
  • Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
  • Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
  • Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

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Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

  • interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
  • an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
  • a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

  • keep track of the search items you use (so that your search can be replicated [10] ),
  • keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
  • use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
  • define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
  • do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

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The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

  • discussing in your review the approaches, limitations, and conclusions of past reviews,
  • trying to find a new angle that has not been covered adequately in the previous reviews, and
  • incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

  • be thorough,
  • use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
  • look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

  • the major achievements in the reviewed field,
  • the main areas of debate, and
  • the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

A comparative review may, e.g., require you to examine two schools of thought, two issues, or the positions taken by two persons. You may create a hierarchy of issues and sub-issues to compare and contrast, as suggested by the following general plan.

This model lists 3 options for structuring the body of the review. In all cases, you are expected to deal with the similarities ( compare ) and then with the differences ( contrast ): Introduction, Body, & Conclusion

Literature Review Example 3 offers an excellent example of  a comparative review [ Language and gender ]. This was written by Alastair Pennycook for his undergraduate students as a model of (among other things) of how to structure a  review of the literature - for an example of the above structure.

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Literature Review: The What, Why and How-to Guide: Evaluating Sources & Literature Reviews

  • Literature Reviews?
  • Strategies to Find Sources
  • Keeping up with Research!
  • Evaluating Sources & Literature Reviews
  • Organizing for Writing
  • Writing Literature Review
  • Other Academic Writings

Evaluating Literature Reviews and Sources

  • Tips for Evaluating Sources (Print vs. Internet Sources) Excellent page that will guide you on what to ask to determine if your source is a reliable one. Check the other topics in the guide: Evaluating Bibliographic Citations and Evaluation During Reading on the left side menu.

Criteria to evaluate sources:

  • Authority : Who is the author? What are the author's credentials and areas of expertise? Is he or she affiliated with a university?
  • Usefulness : How this source related to your topic? How current or relevant it is to your topic?
  • Reliability : Does the information comes from a reliable, trusted source such as an academic journal?
  • Critically Analyzing Information Sources: Critical Appraisal and Analysis (Cornell University Library) Ten things to look for when you evaluate an information source.

Reading Critically

Reading critically (summary from how to read academic texts critically).

  • Who is the author? What is his/her standing in the field?
  • What is the author’s purpose? To offer advice, make practical suggestions, solve a specific problem, critique or clarify?
  • Note the experts in the field: are there specific names/labs that are frequently cited?
  • Pay attention to methodology: is it sound? what testing procedures, subjects, materials were used?
  • Note conflicting theories, methodologies, and results. Are there any assumptions being made by most/some researchers?
  • Theories: have they evolved over time?
  • Evaluate and synthesize the findings and conclusions. How does this study contribute to your project?
  • How to Read Academic Texts Critically Excellent document about how best to read critically academic articles and other texts.
  • How to Read an Academic Article This is an excellent paper that teach you how to read an academic paper, how to determine if it is something to set aside, or something to read deeply. Good advice to organize your literature for the Literature Review or just reading for classes.
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Literature Reviews

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What is a literature review?

A literature review discusses published information in a particular subject area. Often part of the introduction to an essay, research report or thesis, the literature review is literally a "re" view or "look again" at what has already been written about the topic, wherein the author analyzes a segment of a published body of knowledge through summary, classification, and comparison of prior research studies, reviews of literature, and theoretical articles. Literature reviews provide the reader with a bibliographic history of the scholarly research in any given field of study. As such,  as new information becomes available, literature reviews grow in length or become focused on one specific aspect of the topic.

A literature review can be just a simple summary of the sources, but usually contains an organizational pattern and combines both summary and synthesis. A summary is a recap of the important information of the source, whereas a synthesis is a re-organization, or a reshuffling, of that information. The literature review might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. Depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

A literature review is NOT:

  • An annotated bibliography – a list of citations to books, articles and documents that includes a brief description and evaluation for each citation. The annotations inform the reader of the relevance, accuracy and quality of the sources cited.
  • A literary review – a critical discussion of the merits and weaknesses of a literary work.
  • A book review – a critical discussion of the merits and weaknesses of a particular book.
  • Teaching Information Literacy Reframed: 50+ Framework-Based Exercises for Creating Information-Literate Learners
  • The UNC Writing Center – Literature Reviews
  • The UW-Madison Writing Center: The Writer’s Handbook – Academic and Professional Writing – Learn How to Write a Literature Review

What is the difference between a literature review and a research paper?

The focus of a literature review is to summarize and synthesize the arguments and ideas of others without adding new contributions, whereas academic research papers present and develop new arguments that build upon the previously available body of literature.

How do I write a literature review?

There are many resources that offer step-by-step guidance for writing a literature review, and you can find some of them under Other Resources in the menu to the left. Writing the Literature Review: A Practical Guide suggests these steps:

  • Chose a review topic and develop a research question
  • Locate and organize research sources
  • Select, analyze and annotate sources
  • Evaluate research articles and other documents
  • Structure and organize the literature review
  • Develop arguments and supporting claims
  • Synthesize and interpret the literature
  • Put it all together

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What is the purpose of writing a literature review?

Literature reviews serve as a guide to a particular topic: professionals can use literature reviews to keep current on their field; scholars can determine credibility of the writer in his or her field by analyzing the literature review.

As a writer, you will use the literature review to:

  • See what has, and what has not, been investigated about your topic
  • Identify data sources that other researches have used
  • Learn how others in the field have defined and measured key concepts
  • Establish context, or background, for the argument explored in the rest of a paper
  • Explain what the strengths and weaknesses of that knowledge and ideas might be
  • Contribute to the field by moving research forward
  • To keep the writer/reader up to date with current developments in a particular field of study
  • Develop alternative research projects
  • Put your work in perspective
  • Demonstrate your understanding and your ability to critically evaluate research in the field
  • Provide evidence that may support your own findings
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Evidence-Based Practice (EBP)

  • The EBP Process
  • Forming a Clinical Question
  • Inclusion & Exclusion Criteria
  • Acquiring Evidence
  • Appraising the Quality of the Evidence
  • Writing a Literature Review
  • Finding Psychological Tests & Assessment Instruments

What Is a Literature Review?

A literature review is an integrated analysis of scholarly writings that are related directly to your research question. Put simply, it's  a critical evaluation of what's already been written on a particular topic . It represents the literature that provides background information on your topic and shows a connection between those writings 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.

What a Literature Review Is Not:

  • A list or summary of sources
  • An annotated bibliography
  • A grouping of broad, unrelated sources
  • A compilation of everything that has been written on a particular topic
  • Literary criticism (think English) or a book review

Why Literature Reviews Are Important

  • They explain the background of research on a topic
  • They demonstrate why a topic is significant to a subject area
  • They discover relationships between research studies/ideas
  • They identify major themes, concepts, and researchers on a topic
  • They identify critical gaps and points of disagreement
  • They discuss further research questions that logically come out of the previous studies

To Learn More about Conducting and Writing a Lit Review . . .

Monash University (in Australia) has created several extremely helpful, interactive tutorials. 

  • The Stand-Alone Literature Review, https://www.monash.edu/rlo/assignment-samples/science/stand-alone-literature-review
  • Researching for Your Literature Review,  https://guides.lib.monash.edu/researching-for-your-literature-review/home
  • Writing a Literature Review,  https://www.monash.edu/rlo/graduate-research-writing/write-the-thesis/writing-a-literature-review

Keep Track of Your Sources!

A citation manager can be helpful way to work with large numbers of citations. See UMSL Libraries' Citing Sources guide for more information. Personally, I highly recommend Zotero —it's free, easy to use, and versatile. If you need help getting started with Zotero or one of the other citation managers, please contact a librarian.

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  • URL: https://libguides.umsl.edu/ebp

The Writing Center • University of North Carolina at Chapel Hill

Literature Reviews

What this handout is about.

This handout will explain what literature reviews are and offer insights into the form and construction of literature reviews in the humanities, social sciences, and sciences.

Introduction

OK. You’ve got to write a literature review. You dust off a novel and a book of poetry, settle down in your chair, and get ready to issue a “thumbs up” or “thumbs down” as you leaf through the pages. “Literature review” done. Right?

Wrong! The “literature” of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. “Literature” could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL. And a review does not necessarily mean that your reader wants you to give your personal opinion on whether or not you liked these sources.

What is a literature review, then?

A literature review discusses published information in a particular subject area, and sometimes information in a particular subject area within a certain time period.

A literature review can be just a simple summary of the sources, but it usually has an organizational pattern and combines both summary and synthesis. 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. It might give a new interpretation of old material or combine new with old interpretations. Or it might trace the intellectual progression of the field, including major debates. And depending on the situation, the literature review may evaluate the sources and advise the reader on the most pertinent or relevant.

But how is a literature review different from an academic research paper?

The main focus of an academic research paper is to develop a new argument, and a research paper is likely to contain a literature review as one of its parts. In a research paper, you use the literature as a foundation and as support for a new insight that you contribute. The focus of a literature review, however, is to summarize and synthesize the arguments and ideas of others without adding new contributions.

Why do we write literature reviews?

Literature reviews provide you with a handy guide to a particular topic. If you have limited time to conduct research, literature reviews can give you an overview or act as a stepping stone. For professionals, they are useful reports that keep them up to date with what is current in the field. For scholars, the depth and breadth of the literature review emphasizes the credibility of the writer in his or her field. Literature reviews also provide a solid background for a research paper’s investigation. Comprehensive knowledge of the literature of the field is essential to most research papers.

Who writes these things, anyway?

Literature reviews are written occasionally in the humanities, but mostly in the sciences and social sciences; in experiment and lab reports, they constitute a section of the paper. Sometimes a literature review is written as a paper in itself.

Let’s get to it! What should I do before writing the literature review?

If your assignment is not very specific, seek clarification from your instructor:

  • Roughly how many sources should you include?
  • What types of sources (books, journal articles, websites)?
  • Should you summarize, synthesize, or critique your sources by discussing a common theme or issue?
  • Should you evaluate your sources?
  • Should you provide subheadings and other background information, such as definitions and/or a history?

Find models

Look for other literature reviews in your area of interest or in the discipline and read them to get a sense of the types of themes you might want to look for in your own research or ways to organize your final review. You can simply put the word “review” in your search engine along with your other topic terms to find articles of this type on the Internet or in an electronic database. The bibliography or reference section of sources you’ve already read are also excellent entry points into your own research.

Narrow your topic

There are hundreds or even thousands of articles and books on most areas of study. The narrower your topic, the easier it will be to limit the number of sources you need to read in order to get a good survey of the material. Your instructor will probably not expect you to read everything that’s out there on the topic, but you’ll make your job easier if you first limit your scope.

Keep in mind that UNC Libraries have research guides and to databases relevant to many fields of study. You can reach out to the subject librarian for a consultation: https://library.unc.edu/support/consultations/ .

And don’t forget to tap into your professor’s (or other professors’) knowledge in the field. Ask your professor questions such as: “If you had to read only one book from the 90’s on topic X, what would it be?” Questions such as this help you to find and determine quickly the most seminal pieces in the field.

Consider whether your sources are current

Some disciplines require that you use information that is as current as possible. In the sciences, for instance, treatments for medical problems are constantly changing according to the latest studies. Information even two years old could be obsolete. However, if you are writing a review in the humanities, history, or social sciences, a survey of the history of the literature may be what is needed, because what is important is how perspectives have changed through the years or within a certain time period. Try sorting through some 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 consider what is currently of interest to scholars in this field and what is not.

Strategies for writing the literature review

Find a focus.

A literature review, like a term paper, is usually organized around ideas, not the sources themselves as an annotated bibliography would be organized. This means that you will not just simply list your sources and go into detail about each one of them, one at a time. No. As you read widely but selectively in your topic area, consider instead what themes or issues connect your sources together. Do they present one or different solutions? Is there an aspect of the field that is missing? How well do they present the material and do they portray it according to an appropriate theory? Do they reveal a trend in the field? A raging debate? Pick one of these themes to focus the organization of your review.

Convey it to your reader

A literature review may not have a traditional thesis statement (one that makes an argument), but you do need to tell readers what to expect. Try writing a simple statement that lets the reader know what is your main organizing principle. Here are a couple of examples:

The current trend in treatment for congestive heart failure combines surgery and medicine. More and more cultural studies scholars are accepting popular media as a subject worthy of academic consideration.

Consider organization

You’ve got a focus, and you’ve stated it clearly and directly. Now what is the most effective way of presenting the information? What are the most important topics, subtopics, etc., that your review needs to include? And in what order should you present them? Develop an organization for your review at both a global and local level:

First, cover the basic categories

Just like most academic papers, literature reviews also must contain at least three basic elements: an introduction or background information section; the body of the review containing the discussion of sources; and, finally, a conclusion and/or recommendations section to end the paper. The following provides a brief description of the content of each:

  • Introduction: Gives a quick idea of the topic of the literature review, such as the central theme or organizational pattern.
  • Body: Contains your discussion of sources and is organized either chronologically, thematically, or methodologically (see below for more information on each).
  • Conclusions/Recommendations: Discuss what you have drawn from reviewing literature so far. Where might the discussion proceed?

Organizing the body

Once you have the basic categories in place, then you must consider how you will present the sources themselves within the body of your paper. Create an organizational method to focus this section even further.

To help you come up with an overall organizational framework for your review, consider the following scenario:

You’ve decided to focus your literature review on materials dealing with sperm whales. This is because you’ve just finished reading Moby Dick, and you wonder if that whale’s portrayal is really real. You start with some articles about the physiology of sperm whales in biology journals written in the 1980’s. But these articles refer to some British biological studies performed on whales in the early 18th century. So you check those out. Then you look up a book written in 1968 with information on how sperm whales have been portrayed in other forms of art, such as in Alaskan poetry, in French painting, or on whale bone, as the whale hunters in the late 19th century used to do. This makes you wonder about American whaling methods during the time portrayed in Moby Dick, so you find some academic articles published in the last five years on how accurately Herman Melville portrayed the whaling scene in his novel.

Now consider some typical ways of organizing the sources into a review:

  • Chronological: If your review follows the chronological method, you could write about the materials above according to when they were published. For instance, first you would talk about the British biological studies of the 18th century, then about Moby Dick, published in 1851, then the book on sperm whales in other art (1968), and finally the biology articles (1980s) and the recent articles on American whaling of the 19th century. But there is relatively no continuity among subjects here. And notice that even though the sources on sperm whales in other art and on American whaling are written recently, they are about other subjects/objects that were created much earlier. Thus, the review loses its chronological focus.
  • 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 biological studies of sperm whales if the progression revealed a change in dissection practices of the researchers who wrote and/or conducted the studies.
  • By trend: A better way to organize the above sources chronologically is to examine the sources under another trend, such as the history of whaling. Then your review would have subsections according to eras within this period. For instance, the review might examine whaling from pre-1600-1699, 1700-1799, and 1800-1899. Under this method, you would combine the recent studies on American whaling in the 19th century with Moby Dick itself in the 1800-1899 category, even though the authors wrote a century apart.
  • Thematic: Thematic reviews of literature are organized around a topic or issue, rather than the progression of time. However, progression of time may still be an important factor in a thematic review. For instance, the sperm whale review could focus on the development of the harpoon for whale hunting. While the study focuses on one topic, harpoon technology, it will still be organized chronologically. The only difference here between a “chronological” and a “thematic” approach is what is emphasized the most: the development of the harpoon or the harpoon technology.But more authentic thematic reviews tend to break away from chronological order. For instance, a thematic review of material on sperm whales might examine how they are portrayed as “evil” in cultural documents. The subsections might include how they are personified, how their proportions are exaggerated, and their behaviors misunderstood. A review organized in this manner would shift between time periods within each section according to the point made.
  • Methodological: A methodological approach differs from the two above in that the focusing factor usually does not have to do with the content of the material. Instead, it focuses on the “methods” of the researcher or writer. For the sperm whale project, one methodological approach would be to look at cultural differences between the portrayal of whales in American, British, and French art work. Or the review might focus on the economic impact of whaling on a community. A methodological scope will influence either the types of documents in the review or the way in which these documents are discussed. Once you’ve decided on the organizational method for the body of the review, the sections you need to include in the paper should be easy to figure out. They should arise out of 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.

Sometimes, though, you might 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. Put in only what is necessary. Here are a few other sections you might want to consider:

  • Current Situation: Information necessary to understand the topic or focus of the literature review.
  • History: The chronological progression of the field, the literature, or an idea that is necessary to understand the literature review, if the body of the literature review is not already a chronology.
  • Methods and/or Standards: The criteria you used to select the sources in your literature review or the way in which you present your information. For instance, you might explain that your review includes only peer-reviewed articles and journals.

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?

Begin composing

Once you’ve settled on a general pattern of organization, you’re ready to write each section. There are a few guidelines you should follow during the writing stage as well. Here is a sample paragraph from a literature review about sexism and language to illuminate the following discussion:

However, other studies have shown that even gender-neutral antecedents are more likely to produce masculine images than feminine ones (Gastil, 1990). Hamilton (1988) asked students to complete sentences that required them to fill in pronouns that agreed with gender-neutral antecedents such as “writer,” “pedestrian,” and “persons.” The students were asked to describe any image they had when writing the sentence. Hamilton found that people imagined 3.3 men to each woman in the masculine “generic” condition and 1.5 men per woman in the unbiased condition. Thus, while ambient sexism accounted for some of the masculine bias, sexist language amplified the effect. (Source: Erika Falk and Jordan Mills, “Why Sexist Language Affects Persuasion: The Role of Homophily, Intended Audience, and Offense,” Women and Language19:2).

Use evidence

In the example above, the writers refer to several other sources when making their point. A literature review in this sense is just like any other academic research paper. Your interpretation of the available sources must be backed up with evidence to show 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 review’s focus, whether it is thematic, methodological, or chronological.

Use quotes sparingly

Falk and Mills do not use any direct quotes. That is because the survey nature of the literature review does not allow for in-depth discussion or detailed quotes from the text. Some short quotes here and there are okay, though, if you want to emphasize a point, or if what the author said just cannot be rewritten in your own words. Notice that Falk and Mills do quote certain terms that were coined by the author, not common knowledge, or taken directly from the study. But if you find yourself wanting to put in more quotes, check with your instructor.

Summarize and synthesize

Remember to summarize and synthesize your sources within each paragraph as well as throughout the review. The authors here recapitulate important features of Hamilton’s study, but then synthesize it by rephrasing the study’s significance and relating it to their own work.

Keep your own voice

While the literature review presents others’ ideas, your voice (the writer’s) should remain front and center. Notice that Falk and Mills weave references to other sources into their own text, but they still maintain their own voice by starting and ending the paragraph with their own ideas and their own words. The sources support what Falk and Mills are saying.

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. In the preceding example, Falk and Mills either directly refer in the text to the author of their source, such as Hamilton, or they provide ample notation in the text when the ideas they are mentioning are not their own, for example, Gastil’s. For more information, please see our handout on plagiarism .

Revise, revise, revise

Draft in hand? Now you’re ready to revise. Spending a lot of time revising is a wise idea, because your main objective is to present the material, not the argument. So check over your review again to make sure it follows the assignment and/or your outline. Then, just as you would for most other academic forms of writing, rewrite or rework the language of your review so that you’ve presented your information in the most concise manner possible. Be sure to use terminology familiar to your audience; get rid of unnecessary jargon or slang. Finally, double check that you’ve documented your sources and formatted the review appropriately for your discipline. For tips on the revising and editing process, see our handout on revising drafts .

Works consulted

We consulted these works while writing this handout. This is not a comprehensive list of resources on the handout’s topic, and we encourage you to do your own research to find additional publications. Please do not use this list as a model for the format of your own reference list, as it may not match the citation style you are using. For guidance on formatting citations, please see the UNC Libraries citation tutorial . We revise these tips periodically and welcome feedback.

Anson, Chris M., and Robert A. Schwegler. 2010. The Longman Handbook for Writers and Readers , 6th ed. New York: Longman.

Jones, Robert, Patrick Bizzaro, and Cynthia Selfe. 1997. The Harcourt Brace Guide to Writing in the Disciplines . New York: Harcourt Brace.

Lamb, Sandra E. 1998. How to Write It: A Complete Guide to Everything You’ll Ever Write . Berkeley: Ten Speed Press.

Rosen, Leonard J., and Laurence Behrens. 2003. The Allyn & Bacon Handbook , 5th ed. New York: Longman.

Troyka, Lynn Quittman, and Doug Hesse. 2016. Simon and Schuster Handbook for Writers , 11th ed. London: Pearson.

You may reproduce it for non-commercial use if you use the entire handout and attribute the source: The Writing Center, University of North Carolina at Chapel Hill

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  • Comparing and contrasting in an essay | Tips & examples

Comparing and Contrasting in an Essay | Tips & Examples

Published on August 6, 2020 by Jack Caulfield . Revised on July 23, 2023.

Comparing and contrasting is an important skill in academic writing . It involves taking two or more subjects and analyzing the differences and similarities between them.

Table of contents

When should i compare and contrast, making effective comparisons, comparing and contrasting as a brainstorming tool, structuring your comparisons, other interesting articles, frequently asked questions about comparing and contrasting.

Many assignments will invite you to make comparisons quite explicitly, as in these prompts.

  • Compare the treatment of the theme of beauty in the poetry of William Wordsworth and John Keats.
  • Compare and contrast in-class and distance learning. What are the advantages and disadvantages of each approach?

Some other prompts may not directly ask you to compare and contrast, but present you with a topic where comparing and contrasting could be a good approach.

One way to approach this essay might be to contrast the situation before the Great Depression with the situation during it, to highlight how large a difference it made.

Comparing and contrasting is also used in all kinds of academic contexts where it’s not explicitly prompted. For example, a literature review involves comparing and contrasting different studies on your topic, and an argumentative essay may involve weighing up the pros and cons of different arguments.

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As the name suggests, comparing and contrasting is about identifying both similarities and differences. You might focus on contrasting quite different subjects or comparing subjects with a lot in common—but there must be some grounds for comparison in the first place.

For example, you might contrast French society before and after the French Revolution; you’d likely find many differences, but there would be a valid basis for comparison. However, if you contrasted pre-revolutionary France with Han-dynasty China, your reader might wonder why you chose to compare these two societies.

This is why it’s important to clarify the point of your comparisons by writing a focused thesis statement . Every element of an essay should serve your central argument in some way. Consider what you’re trying to accomplish with any comparisons you make, and be sure to make this clear to the reader.

Comparing and contrasting can be a useful tool to help organize your thoughts before you begin writing any type of academic text. You might use it to compare different theories and approaches you’ve encountered in your preliminary research, for example.

Let’s say your research involves the competing psychological approaches of behaviorism and cognitive psychology. You might make a table to summarize the key differences between them.

Or say you’re writing about the major global conflicts of the twentieth century. You might visualize the key similarities and differences in a Venn diagram.

A Venn diagram showing the similarities and differences between World War I, World War II, and the Cold War.

These visualizations wouldn’t make it into your actual writing, so they don’t have to be very formal in terms of phrasing or presentation. The point of comparing and contrasting at this stage is to help you organize and shape your ideas to aid you in structuring your arguments.

When comparing and contrasting in an essay, there are two main ways to structure your comparisons: the alternating method and the block method.

The alternating method

In the alternating method, you structure your text according to what aspect you’re comparing. You cover both your subjects side by side in terms of a specific point of comparison. Your text is structured like this:

Mouse over the example paragraph below to see how this approach works.

One challenge teachers face is identifying and assisting students who are struggling without disrupting the rest of the class. In a traditional classroom environment, the teacher can easily identify when a student is struggling based on their demeanor in class or simply by regularly checking on students during exercises. They can then offer assistance quietly during the exercise or discuss it further after class. Meanwhile, in a Zoom-based class, the lack of physical presence makes it more difficult to pay attention to individual students’ responses and notice frustrations, and there is less flexibility to speak with students privately to offer assistance. In this case, therefore, the traditional classroom environment holds the advantage, although it appears likely that aiding students in a virtual classroom environment will become easier as the technology, and teachers’ familiarity with it, improves.

The block method

In the block method, you cover each of the overall subjects you’re comparing in a block. You say everything you have to say about your first subject, then discuss your second subject, making comparisons and contrasts back to the things you’ve already said about the first. Your text is structured like this:

  • Point of comparison A
  • Point of comparison B

The most commonly cited advantage of distance learning is the flexibility and accessibility it offers. Rather than being required to travel to a specific location every week (and to live near enough to feasibly do so), students can participate from anywhere with an internet connection. This allows not only for a wider geographical spread of students but for the possibility of studying while travelling. However, distance learning presents its own accessibility challenges; not all students have a stable internet connection and a computer or other device with which to participate in online classes, and less technologically literate students and teachers may struggle with the technical aspects of class participation. Furthermore, discomfort and distractions can hinder an individual student’s ability to engage with the class from home, creating divergent learning experiences for different students. Distance learning, then, seems to improve accessibility in some ways while representing a step backwards in others.

Note that these two methods can be combined; these two example paragraphs could both be part of the same essay, but it’s wise to use an essay outline to plan out which approach you’re taking in each paragraph.

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Some essay prompts include the keywords “compare” and/or “contrast.” In these cases, an essay structured around comparing and contrasting is the appropriate response.

Comparing and contrasting is also a useful approach in all kinds of academic writing : You might compare different studies in a literature review , weigh up different arguments in an argumentative essay , or consider different theoretical approaches in a theoretical framework .

Your subjects might be very different or quite similar, but it’s important that there be meaningful grounds for comparison . You can probably describe many differences between a cat and a bicycle, but there isn’t really any connection between them to justify the comparison.

You’ll have to write a thesis statement explaining the central point you want to make in your essay , so be sure to know in advance what connects your subjects and makes them worth comparing.

Comparisons in essays are generally structured in one of two ways:

  • The alternating method, where you compare your subjects side by side according to one specific aspect at a time.
  • The block method, where you cover each subject separately in its entirety.

It’s also possible to combine both methods, for example by writing a full paragraph on each of your topics and then a final paragraph contrasting the two according to a specific metric.

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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.

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.

Literature review guide

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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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comparison and literature review

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 !

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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 Write a Literature Review

What is a literature review.

  • What Is the Literature
  • Writing the Review

A literature review is much more than an annotated bibliography or a list of separate reviews of articles and books. It is a critical, analytical summary and synthesis of the current knowledge of a topic. Thus it should compare and relate different theories, findings, etc, rather than just summarize them individually. In addition, it should have a particular focus or theme to organize the review. It does not have to be an exhaustive account of everything published on the topic, but it should discuss all the significant academic literature and other relevant sources important for that focus.

This is meant to be a general guide to writing a literature review: ways to structure one, what to include, how it supplements other research. For more specific help on writing a review, and especially for help on finding the literature to review, sign up for a Personal Research Session .

The specific organization of a literature review depends on the type and purpose of the review, as well as on the specific field or topic being reviewed. But in general, it is a relatively brief but thorough exploration of past and current work on a topic. Rather than a chronological listing of previous work, though, literature reviews are usually organized thematically, such as different theoretical approaches, methodologies, or specific issues or concepts involved in the topic. A thematic organization makes it much easier to examine contrasting perspectives, theoretical approaches, methodologies, findings, etc, and to analyze the strengths and weaknesses of, and point out any gaps in, previous research. And this is the heart of what a literature review is about. A literature review may offer new interpretations, theoretical approaches, or other ideas; if it is part of a research proposal or report it should demonstrate the relationship of the proposed or reported research to others' work; but whatever else it does, it must provide a critical overview of the current state of research efforts. 

Literature reviews are common and very important in the sciences and social sciences. They are less common and have a less important role in the humanities, but they do have a place, especially stand-alone reviews.

Types of Literature Reviews

There are different types of literature reviews, and different purposes for writing a review, but the most common are:

  • Stand-alone literature review articles . These provide an overview and analysis of the current state of research on a topic or question. The goal is to evaluate and compare previous research on a topic to provide an analysis of what is currently known, and also to reveal controversies, weaknesses, and gaps in current work, thus pointing to directions for future research. You can find examples published in any number of academic journals, but there is a series of Annual Reviews of *Subject* which are specifically devoted to literature review articles. Writing a stand-alone review is often an effective way to get a good handle on a topic and to develop ideas for your own research program. For example, contrasting theoretical approaches or conflicting interpretations of findings can be the basis of your research project: can you find evidence supporting one interpretation against another, or can you propose an alternative interpretation that overcomes their limitations?
  • Part of a research proposal . This could be a proposal for a PhD dissertation, a senior thesis, or a class project. It could also be a submission for a grant. The literature review, by pointing out the current issues and questions concerning a topic, is a crucial part of demonstrating how your proposed research will contribute to the field, and thus of convincing your thesis committee to allow you to pursue the topic of your interest or a funding agency to pay for your research efforts.
  • Part of a research report . When you finish your research and write your thesis or paper to present your findings, it should include a literature review to provide the context to which your work is a contribution. Your report, in addition to detailing the methods, results, etc. of your research, should show how your work relates to others' work.

A literature review for a research report is often a revision of the review for a research proposal, which can be a revision of a stand-alone review. Each revision should be a fairly extensive revision. With the increased knowledge of and experience in the topic as you proceed, your understanding of the topic will increase. Thus, you will be in a better position to analyze and critique the literature. In addition, your focus will change as you proceed in your research. Some areas of the literature you initially reviewed will be marginal or irrelevant for your eventual research, and you will need to explore other areas more thoroughly. 

Examples of Literature Reviews

See the series of Annual Reviews of *Subject* which are specifically devoted to literature review articles to find many examples of stand-alone literature reviews in the biomedical, physical, and social sciences. 

Research report articles vary in how they are organized, but a common general structure is to have sections such as:

  • Abstract - Brief summary of the contents of the article
  • Introduction - A explanation of the purpose of the study, a statement of the research question(s) the study intends to address
  • Literature review - A critical assessment of the work done so far on this topic, to show how the current study relates to what has already been done
  • Methods - How the study was carried out (e.g. instruments or equipment, procedures, methods to gather and analyze data)
  • Results - What was found in the course of the study
  • Discussion - What do the results mean
  • Conclusion - State the conclusions and implications of the results, and discuss how it relates to the work reviewed in the literature review; also, point to directions for further work in the area

Here are some articles that illustrate variations on this theme. There is no need to read the entire articles (unless the contents interest you); just quickly browse through to see the sections, and see how each section is introduced and what is contained in them.

The Determinants of Undergraduate Grade Point Average: The Relative Importance of Family Background, High School Resources, and Peer Group Effects , in The Journal of Human Resources , v. 34 no. 2 (Spring 1999), p. 268-293.

This article has a standard breakdown of sections:

  • Introduction
  • Literature Review
  • Some discussion sections

First Encounters of the Bureaucratic Kind: Early Freshman Experiences with a Campus Bureaucracy , in The Journal of Higher Education , v. 67 no. 6 (Nov-Dec 1996), p. 660-691.

This one does not have a section specifically labeled as a "literature review" or "review of the literature," but the first few sections cite a long list of other sources discussing previous research in the area before the authors present their own study they are reporting.

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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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Systematic, Scoping, and Other Literature Reviews: Overview

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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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Systematic and scoping reviews: A comparison and overview

Affiliations.

  • 1 Division of Vascular Surgery, Western University, London, Ontario, Canada.
  • 2 Division of Vascular Surgery, Western University, London, Ontario, Canada. Electronic address: [email protected].
  • PMID: 36414363
  • DOI: 10.1053/j.semvascsurg.2022.09.001

In this article, we compare and contrast methods of reviewing, summarizing, and synthesizing the literature, including systematic reviews, scoping reviews, and narrative reviews. Review articles are essential to help investigators wade through the plethora of exponentially growing medical literature. In the era of evidence-based medicine, a systematic approach is required. A systematic review is a formalized method to address a specific clinical question by analyzing the breadth of published literature while minimizing bias. Systematic reviews are designed to answer narrow clinical questions in the PICO (population, intervention, comparison, and outcome) format. Alternatively, scoping reviews use a similar systematic approach to a literature search in order to determine the breadth and depth of knowledge on a topic; to clarify definitions, concepts, and themes; or sometimes as a precursor to a systematic review or hypothesis generator to guide future research. However, scoping reviews are less constrained by a priori decisions about which interventions, controls, and outcomes may be of interest. Traditional narrative reviews still have a role in informing practice and guiding research, particularly when there is a paucity of high-quality evidence on a topic.

Copyright © 2022. Published by Elsevier Inc.

Publication types

  • Systematic Review
  • Evidence-Based Medicine*
  • Research Design*

Literature Review vs Systematic Review

  • Literature Review vs. Systematic Review
  • Primary vs. Secondary Sources
  • Databases and Articles
  • Specific Journal or Article

Subject Guide

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Definitions

It’s common to confuse systematic and literature reviews because both are used to provide a summary of the existent literature or research on a specific topic. Regardless of this commonality, both types of review vary significantly. The following table provides a detailed explanation as well as the differences between systematic and literature reviews. 

Kysh, Lynn (2013): Difference between a systematic review and a literature review. [figshare]. Available at:  http://dx.doi.org/10.6084/m9.figshare.766364

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  • Last Updated: Dec 15, 2023 10:19 AM
  • URL: https://libguides.sjsu.edu/LitRevVSSysRev

ON YOUR 1ST ORDER

Different Types of Literature Review: Which One Fits Your Research?

By Laura Brown on 13th October 2023

You might not have heard that there are multiple kinds of literature review. However, with the progress in your academic career you will learn these classifications and may need to use different types of them. However, there is nothing to worry if you aren’t aware of them now, as here we are going to discuss this topic in detail.

There are approximately 14 types of literature review on the basis of their specific objectives, methodologies, and the way they approach and analyse existing literature in academic research. Of those 14, there are 4 major types. But before we delve into the details of each one of them and how they are useful in academics, let’s first understand the basics of literature review.

Demystifying 14 Different Types of Literature Reviews

What is Literature Review?

A literature review is a critical and systematic summary and evaluation of existing research. It is an essential component of academic and research work, providing an overview of the current state of knowledge in a particular field.

In easy words, a literature review is like making a big, organised summary of all the important research and smart books or articles about a particular topic or question. It’s something scholars and researchers do, and it helps everyone see what we already know about that topic. It’s kind of like taking a snapshot of what we understand right now in a certain field.

It serves with some specific purpose in the research.

  • Provides a comprehensive understanding of existing research on a topic.
  • Identifies gaps, trends, and inconsistencies in the literature.
  • Contextualise your own research within the broader academic discourse.
  • Supports the development of theoretical frameworks or research hypotheses.

4 Major Types Of Literature Review

The four major types include, Narrative Review, Systematic Review, Meta-Analysis, and Scoping Review. These are known as the major ones because they’re like the “go-to” methods for researchers in academic and research circles. Think of them as the classic tools in the researcher’s toolbox. They’ve earned their reputation because they have a unique style for literature review introduction , clear steps and specific qualities that make them super handy for different research needs.

1. Narrative Review

Narrative reviews present a well-structured narrative that reads like a cohesive story, providing a comprehensive overview of a specific topic. These reviews often incorporate historical context and offer a broad understanding of the subject matter, making them valuable for researchers looking to establish a foundational understanding of their area of interest. They are particularly useful when a historical perspective or a broad context is necessary to comprehend the current state of knowledge in a field.

2. Systematic Review

Systematic reviews are renowned for their methodological rigour. They involve a meticulously structured process that includes the systematic selection of relevant studies, comprehensive data extraction, and a critical synthesis of their findings. This systematic approach is designed to minimise bias and subjectivity, making systematic reviews highly reliable and objective. They are considered the gold standard for evidence-based research as they provide a clear and rigorous assessment of the available evidence on a specific research question.

3. Meta Analysis

Meta analysis is a powerful method for researchers who prefer a quantitative and statistical perspective. It involves the statistical synthesis of data from various studies, allowing researchers to draw more precise and generalisable conclusions by combining data from multiple sources. Meta analyses are especially valuable when the aim is to quantitatively measure the effect size or impact of a particular intervention, treatment, or phenomenon.

4. Scoping Review

Scoping reviews are invaluable tools, especially for researchers in the early stages of exploring a topic. These reviews aim to map the existing literature, identifying gaps and helping clarify research questions. Scoping reviews provide a panoramic view of the available research, which is particularly useful when researchers are embarking on exploratory studies or trying to understand the breadth and depth of a subject before conducting more focused research.

Different Types Of Literature review In Research

There are some more approaches to conduct literature review. Let’s explore these classifications quickly.

5. Critical Review

Critical reviews provide an in-depth evaluation of existing literature, scrutinising sources for their strengths, weaknesses, and relevance. They offer a critical perspective, often highlighting gaps in the research and areas for further investigation.

6. Theoretical Review

Theoretical reviews are centred around exploring and analysing the theoretical frameworks, concepts, and models present in the literature. They aim to contribute to the development and refinement of theoretical perspectives within a specific field.

7. Integrative Review

Integrative reviews synthesise a diverse range of studies, drawing connections between various research findings to create a comprehensive understanding of a topic. These reviews often bridge gaps between different perspectives and provide a holistic overview.

8. Historical Review

Historical reviews focus on the evolution of a topic over time, tracing its development through past research, events, and scholarly contributions. They offer valuable context for understanding the current state of research.

9. Methodological Review

Among the different kinds of literature reviews, methodological reviews delve into the research methods and methodologies employed in existing studies. Researchers assess these approaches for their effectiveness, validity, and relevance to the research question at hand.

10. Cross-Disciplinary Review

Cross-disciplinary reviews explore a topic from multiple academic disciplines, emphasising the diversity of perspectives and insights that each discipline brings. They are particularly useful for interdisciplinary research projects and uncovering connections between seemingly unrelated fields.

11. Descriptive Review

Descriptive reviews provide an organised summary of existing literature without extensive analysis. They offer a straightforward overview of key findings, research methods, and themes present in the reviewed studies.

12. Rapid Review

Rapid reviews expedite the literature review process, focusing on summarising relevant studies quickly. They are often used for time-sensitive projects where efficiency is a priority, without sacrificing quality.

13. Conceptual Review

Conceptual reviews concentrate on clarifying and developing theoretical concepts within a specific field. They address ambiguities or inconsistencies in existing theories, aiming to refine and expand conceptual frameworks.

14. Library Research

Library research reviews rely primarily on library and archival resources to gather and synthesise information. They are often employed in historical or archive-based research projects, utilising library collections and historical documents for in-depth analysis.

Each type of literature review serves distinct purposes and comes with its own set of strengths and weaknesses, allowing researchers to choose the one that best suits their research objectives and questions.

Choosing the Ideal Literature Review Approach in Academics

In order to conduct your research in the right manner, it is important that you choose the correct type of review for your literature. Here are 8 amazing tips we have sorted for you in regard to literature review help so that you can select the best-suited type for your research.

  • Clarify Your Research Goals: Begin by defining your research objectives and what you aim to achieve with the literature review. Are you looking to summarise existing knowledge, identify gaps, or analyse specific data?
  • Understand Different Review Types: Familiarise yourself with different kinds of literature reviews, including systematic reviews, narrative reviews, meta-analyses, scoping reviews, and integrative reviews. Each serves a different purpose.
  • Consider Available Resources: Assess the resources at your disposal, including time, access to databases, and the volume of literature on your topic. Some review types may be more resource-intensive than others.
  • Alignment with Research Question: Ensure that the chosen review type aligns with your research question or hypothesis. Some types are better suited for answering specific research questions than others.
  • Scope and Depth: Determine the scope and depth of your review. For a broad overview, a narrative review might be suitable, while a systematic review is ideal for an in-depth analysis.
  • Consult with Advisors: Seek guidance from your academic advisors or mentors. They can provide valuable insights into which review type best fits your research goals and resources.
  • Consider Research Field Standards: Different academic fields have established standards and preferences for different forms of literature review. Familiarise yourself with what is common and accepted in your field.
  • Pilot Review: Consider conducting a small-scale pilot review of the literature to test the feasibility and suitability of your chosen review type before committing to a larger project.

Bonus Tip: Crafting an Effective Literature Review

Now, since you have learned all the literature review types and have understood which one to prefer, here are some bonus tips for you to structure a literature review of a dissertation .

  • Clearly Define Your Research Question: Start with a well-defined and focused research question to guide your literature review.
  • Thorough Search Strategy: Develop a comprehensive search strategy to ensure you capture all relevant literature.
  • Critical Evaluation: Assess the quality and credibility of the sources you include in your review.
  • Synthesise and Organise: Summarise the key findings and organise the literature into themes or categories.
  • Maintain a Systematic Approach: If conducting a systematic review, adhere to a predefined methodology and reporting guidelines.
  • Engage in Continuous Review: Regularly update your literature review to incorporate new research and maintain relevance.

Some Useful Tools And Resources For You

Effective literature reviews demand a range of tools and resources to streamline the process.

  • Reference management software like EndNote, Zotero, and Mendeley helps organise, store, and cite sources, saving time and ensuring accuracy.
  • Academic databases such as PubMed, Google Scholar, and Web of Science provide access to a vast array of scholarly articles, with advanced search and citation tracking features.
  • Research guides from universities and libraries offer tips and templates for structuring reviews.
  • Research networks like ResearchGate and Academia.edu facilitate collaboration and access to publications. Literature review templates and research workshops provide additional support.

Some Common Mistakes To Avoid

Avoid these common mistakes when crafting literature reviews.

  • Unclear research objectives result in unfocused reviews, so start with well-defined questions.
  • Biased source selection can compromise objectivity, so include diverse perspectives.
  • Never miss on referencing; proper citation and referencing are essential for academic integrity.
  • Don’t overlook older literature, which provides foundational insights.
  • Be mindful of scope creep, where the review drifts from the research question; stay disciplined to maintain focus and relevance.

While Summing Up On Various Types Of Literature Review

As we conclude this classification of fourteen distinct approaches to conduct literature reviews, it’s clear that the world of research offers a multitude of avenues for understanding, analysing, and contributing to existing knowledge.

Whether you’re a seasoned scholar or a student beginning your academic journey, the choice of review type should align with your research objectives and the nature of your topic. The versatility of these approaches empowers you to tailor your review to the demands of your project.

Remember, your research endeavours have the potential to shape the future of knowledge, so choose wisely and dive into the world of literature reviews with confidence and purpose. Happy reviewing!

Laura Brown

Laura Brown, a senior content writer who writes actionable blogs at Crowd Writer.

  • Open access
  • Published: 03 January 2024

A literature review and meta-analysis of the optimal factors study of repetitive transcranial magnetic stimulation in post-infarction aphasia

  • Yang Tan 1   na1 ,
  • Lin-Ming Zhang 2   na1 ,
  • Xing-ling Liang 1   na1 ,
  • Guei-fei Xiong 1 ,
  • Xuan-lin Xing 1 ,
  • Qiu-juan Zhang 1 ,
  • Bing-ran Zhang 1 ,
  • Zi-bin Yang 1 , 3 &
  • Ming-wei Liu 1 , 4  

European Journal of Medical Research volume  29 , Article number:  18 ( 2024 ) Cite this article

Metrics details

The existing literature indicates that repetitive transcranial magnetic stimulation (rTMS) can potentially enhance the prognosis of poststroke aphasia (PSA). Nevertheless, these investigations did not identify the most effective parameters or settings for achieving optimal treatment outcomes. This study involved a meta-analysis aimed to identify the optimal variables for rTMS in treating post-infarction aphasia to guide the use of rTMS in rehabilitating PSA.

PubMed, Embase, and Cochrane Library databases were searched from inception to May 2023, and articles were reviewed manually using subject words and free words and supplemented with references from the included literature to obtain additional relevant literature. The search terms included “poststroke aphasia” and “repetitive transcranial magnetic stimulation (rTMS)” repetitive transcranial magnetic stimulation. Additionally, a review of the reference lists of previously published systematic reviews identified through the Cochrane Database of Systematic Reviews (search terms: poststroke aphasia, rTMS; restrictions: none) and PubMed (search terms: poststroke aphasia, rTMSs; restrictions: systematic review or meta-analysis) was performed. Information from studies involving different doses of rTMS in PSA was independently screened and extracted by 2 researchers.

This meta-analysis included 387 participants with PSA across 18 randomized controlled trials. The results showed that the total pulse had a trend toward a significant correlation with the treatment effect ( P  = 0.088), while all other variables did not correlate significantly. When rTMS was not grouped by stimulus parameter and location, our nonlinear results showed that when the total pulses were 40,000 (standardized mean difference (SMD):1.86, 95% credible interval (CrI) 0.50 to 3.33), the pulse/session was 1000 (SMD:1.05, 95% CrI 0.55–1.57), and an RMT of 80% (SMD:1.08, 95% CrI 0.60–1.57) had the best treatment effect. When rTMS was grouped by stimulus parameters and location, our nonlinear results showed that when the total low-frequency (LF)-rTMS-right inferior frontal gyrus (RIFG) pulse was 40,000 (SMD:1.76, 95% CrI:0.36–3.29), the pulse/session was 1000 (SMD:1.06, 95% CrI:0.54–1.59). Optimal results were obtained with an RMT of 80% (SMD:1.14, 95% CrI 0.54 − 1.76).

Conclusions

The optimal treatment effects of rTMS for PSA may be obtained with a total pulse of 40,000, a pulse/session of 1000, and an RMT of 80%. Further rigorous randomized controlled studies are required to substantiate the validity of these results.

Introduction

Aphasia is a neurological condition characterized by impaired language understanding and expression. It typically develops because of damage to the brain's language centers or associated networks [ 1 ]. Brain tumors, traumatic brain injury, and intracranial infections can induce aphasia, stroke is the main cause, and poststroke aphasia (PSA) is as high as 21–38% [ 2 ]. China has an annual incidence of over 2 million stroke cases and approximately 600,000 incidents of PSA [ 3 ]. In the United States, each year, 7 million people self-report having a stroke, and approximately 100,000 stroke patients are diagnosed with PSA [ 4 ]. Cerebral infarction is the main cause of PSA, and post-infarction aphasia accounts for 62% of PSA cases, with a 4% annual increase in the risk of developing it [ 2 , 5 ]. Aphasia is associated with negative effects such as anxiety [ 6 ], depression [ 7 ], impairment in social participation [ 8 ], and reduced quality of life [ 9 ]. The financial expenses associated with providing care for individuals diagnosed with aphasia are significantly greater than those without aphasia, resulting in a substantial societal burden [ 10 ]. Therefore, language rehabilitation for aphasic patients after cerebral infarction has become an urgent problem in stroke rehabilitation.

Currently, there are three main types of aphasia rehabilitation therapies: pharmacotherapy, behavioral training, and brain neuromodulation. Pharmacological therapies are divided into western and Chinese herbal therapies. Various clinical trials have provided evidence that Western medications, including meperidine, bromocriptine, donepezil, and piracetam, as well as drugs used in Chinese medicine for wind removal, phlegm dissipation, and channel dredging (such as Jieyudan Rod and flavored Jieyudan) may enhance the language function of individuals with aphasia to varying degrees [ 11 , 12 ]. However, both Chinese and Western medications are associated with adverse effects, and current pharmacological treatments combined with behavioral training, neuromodulation, and pharmacological treatment alone have limited efficacy for language rehabilitation in patients with aphasia [ 13 , 14 ]. In recent years, neuromodulation techniques have received increasing attention for the treatment of PSA [ 15 , 16 , 17 , 18 ] because they can promote the reconstruction of functional brain subdivisions and modulate neural network reorganization to exert therapeutic effects. The two primary methods of these procedures are noninvasive and invasive brain stimulation. Invasive brain stimulation is commonly used in acupuncture therapy to expand cerebral blood vessels, increase cerebral blood flow, and improve cerebral ischemia to promote the recovery of language function by needling acupuncture points in the patient’s head [ 17 , 18 ]. Repetitive transcranial magnetic stimulation (rTMS) is the most commonly used noninvasive brain stimulation technique. The principle of this technique in the treatment of aphasia differs from that of acupuncture in that it applies magnetic stimulation of different frequencies to the same cortical area through an electrically charged coil to induce depolarization or hyperpolarization of synaptic cells between neurons in the brain, which in turn affects cortical activity at the stimulation site or distant sites to promote the recovery of language function [ 19 , 20 ]. Studies have confirmed that rTMS can restore homeostasis in the cerebral hemispheres and improve language function in patients with aphasia by changing stimulation frequency [ 20 , 21 , 22 ].

In recent years, many regional and international scholars have used low and high doses of rTMS to modulate interhemispheric interactions and promote language recovery in patients [ 23 ]. However, the optimal variables for achieving the greatest treatment effects remain unclear. Thus, to determine which rTMS settings in post-infarction aphasia resulted in the highest improvement in the rehabilitation of rTMS in the treatment of PSA, a meta-analysis was performed in the current study.

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Network Meta-Analyses (PRISMA-NMA) guidelines were followed during the study methodology [ 24 ]. The protocol number registered in the PROSPERO database is CRD42023437016.

Search strategy

We conducted a systematic search in electronic databases (Appendix 1), such as Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL), PsycINFO, Embase, MEDLINE, and PubMed from their inception dates to May 23, 2023, through the terms ‘repetitive transcranial magnetic stimulation (rTMS)' and Medical Subject Headings (MeSH) for the terms 'poststroke aphasia’. Further investigations involved examining the reference lists of pre-existing systematic reviews that were discovered through the Cochrane Database of Systematic Reviews and PubMed (search terms: poststroke aphasia, rTMS; limitations: systematic reviews or meta-analyses) and, respectively (poststroke aphasia, rTMS; limits: none). Ethnicity and language of the trial participants were not filtered. Before being included in the search results, Ming-wei Liu eliminated any duplicates. Ming-Wei Liu and Lin-ming Zhang independently screened the titles and abstracts of the remaining articles, adhering to the predetermined inclusion and exclusion criteria. Liang and Xiong independently screened the complete texts that satisfied the abovementioned criteria. Ming-wei Liu served as the referee for all disputes, and the specific search method is presented in the Additional file 1 (see the retrieval strategy).

Eligibility criteria

The criteria for inclusion in the study were determined using the PICOS framework, which considers participants, interventions, comparators, outcomes, and study design [ 1 ]. In order to meet the requirements for inclusion, the research must adhere to particular guidelines on the reporting of experimental variables as follows: (a) participants were diagnosed with poststroke aphasia using standard scales (i.e., the Concise Chinese Aphasia Test, Boston Diagnostic Aphasia Examination, Aphasia Severity Rating Scale, Aachen Aphasia Test, and Aphasia Rapid Test); (b) the intervention included rTMS and advanced variants; (c) comparison of sham placebo therapy or stimulation; (d) the outcome was the total language scale, such as the aphasia quotient (AQ) of the Western Aphasia Battery and Aphasia Battery of Chinese, as well as the overall score of other scales; and (e) we included published and unpublished RCTs.

Studies were excluded based on the following criteria: (a) they had a nonrandomized design; (b) the study employed therapies that were deemed irrelevant, including invasive procedures such as deep brain stimulation. (c) Means ± standard deviation (SD) were not included in the results or if the authors did not respond to our request for data; (d) the selection of control groups was deemed inappropriate, for example, healthy participants or those involved in other effective treatments; or (c) they did not clearly describe the targeted stimulation location of rTMS, resting motor threshold, or pulses per session. Following the specified criteria for inclusion and exclusion, two reviewers, Ming-wei Liu and Lin-ming Zhang, thoroughly examined potentially pertinent publications. This examination involved assessing the titles, abstracts, and full texts of articles to determine their suitability for inclusion.

Data extraction

Two independent examiners (Ming-wei Liu and Lin-ming Zhang) assembled pertinent publication data, including author, title, year, and journal. In addition, they collected data on the number of patients, patient characteristics including age and sex, interventions examined, and outcome measures; if the original study provided a standard error for the experimental and control groups, the SD was computed using the following formula: standard deviation (SD) = standard error (SE) × √ In situations where both values were absent, the SD was estimated using several statistical measures, such as the confidence interval, t value, quartile, range, or p values, as outlined in Sect. 7.7.3 of the Cochrane Handbook for Systematic Reviews [ 25 ]. To obtain accurate measurements, the data extraction process utilized GetData ( http://getdata-graph-digitizer.com ) to extract the length of the axes in pixels for calibration purposes. Subsequently, the length of the pixels from the pertinent axis to the desired data points is determined. When the procedures mentioned above failed to yield the required data, we initiated contact with the authors on at least four occasions for 6 weeks.

Evaluation of the risk of bias

Two independent reviewers (XD and JZ) evaluated the quality of the included studies using the Cochrane Risk of Bias version 2 tool (RoB2) [ 26 ] and included five domains: selection of reported results, outcome measurement, randomization process, deviations from intended interventions, and missing outcome data. The RoB2 tool incorporates an additional domain, in conjunction with the five existing domains, to evaluate the potential for bias in cluster randomized controlled trials arising from the timing of participant identification and recruitment [ 27 ]. Each area was assessed as (1) high-risk, (2) low-risk, and (3) some concern. If all domains exhibited low risk, each study's collective risk of bias was deemed low. If any of the domains mentioned above exhibited a high level of risk, or if the assessment findings of numerous domains indicated some degree of worry, then the overall risk of bias was deemed high. Conversely, if none of the domains displayed a high risk or the assessment results of many domains did not raise any concerns, the risk of bias was considered low. Disputes were settled by establishing consensus among the reviewers or by involving a third reviewer in the consultation process.

Data synthesis

The rTMS-specific variables included the following: targeted stimulation location in Hz (e.g., low frequency: ≤ 1 Hz, high frequency: > 1 Hz), resting motor threshold (%), pulses/100 per session, and pulses/1000 (total, pulses/session × frequency × period). To verify the effect of these variables on the dose–response relationship of overall language ability on poststroke aphasia, we first performed a linear regression based on the R-environment 'metafor' package (V.4.2.2, www.r-project.org ). In addition, we used the 'MBNMAdose' package to perform random-effects Bayesian model-based network meta-analysis (MBNMA) [ 28 ] to summarize the dose–response association between rTMS-specific variables and overall language ability. There was no indication that any of the key assumptions for network meta-analysis (i.e., connectedness of the network [ 29 ], consistency in the data, and transitivity [ 30 , 31 ]) were violated. We compared the fit indices of a series of nonlinear functions [ 32 ] and finally chose restricted cubic splines to evaluate the nonlinear dose–response association. Based on the model that exhibits the highest level of conformity and biological credibility [ 33 ], we positioned three inflection points at the 10th, 50th, and 90th percentiles of treatment dosage. The assessment of the departure from linearity was conducted using the Wald test[ 34 ]. Given the variations in rating scales and outcome measure units among the included studies, a random-effects model was employed to aggregate the data. The effect size measure chosen for this analysis was the standardized mean difference (SMD), and the post-treatment score was accompanied by 95% credible interval (CrI). According to previous literature [ 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 ], the resting motor threshold ranged from to 80–110%, and rTMS had low frequencies of 0.5 and 1 Hz and a high frequency of 20 Hz. The pulse presessions included 384, 600, 800, 1000, 1200, and 1800 pulses.

Features of the studies that were included

A total of 3841 studies were determined to potentially meet the eligibility criteria after an initial electronic search. Following the initial screening process of citations based on their titles and abstracts, 254 studies were selected as potentially fulfilling eligibility requirements. Subsequently, a thorough search was conducted to acquire the full-text publications of these studies. After excluding papers that did not satisfy the predetermined inclusion criteria, 18 studies [35, 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52] with 387 participants (male:female 170/217) were included in the meta-analysis (Fig.  1 ). The sample sizes of the included studies ranged from 10 to 56. The treatment period ranged from 1 to 8 weeks, the frequency of rTMS treatment per week was 5 times, and the total sessions ranged from 5 to 40 times. The targeted stimulation locations were the right inferior frontal gyrus (RIFG), dual inferior frontal gyrus (DIFG), and right temporoparietal region (RTP) (Table 1 ). An assessment of the quality of the included studies is shown in Table 2 .

figure 1

Process of literature screening

Meta-analysis

Table 3 shows the linear regression of the rTMS-specific variables for overall language ability in the PSA. Only the total pulse volume had an obvious correlation with the treatment effect ( P  = 0.088); no other variables were correlated. When rTMS was not grouped by stimulation parameter and location, our nonlinear results showed that the best therapeutic effect was observed when the total pulse was 40,000 (SMD:1.86, 95% CrI 0.50 to 3.33); pulses/session was 1000 (SMD:1.05, 95% CrI 0.55 to 1.57); and RMT was 80% (SMD:1.08, 95% CrI 0.60 to 1.57) (Fig.  2 ). When rTMS was grouped by stimulation parameter and location, our nonlinear results showed that the best effect was shown when the LF-rTMS-RIFG total pulse was 40000 (SMD:1.76, 95% CrI 0.36 to 3.29); pulses/session was 1000 (SMD:1.06, 95% CrI 0.54 to 1.59); and RMT was 80% (SMD:1.14, 95% CrI 0.54 to 1.76) (Fig.  3 ).

figure 2

Nonlinear analysis of the effects of different total pulses ( A ), pulses/sessions ( B ), and RMT ( C ) in patients with poststroke aphasia treated with rTMS when rTMS is not grouped by stimulation parameter and location

figure 3

Nonlinear analysis of the effects of different total pulses ( A ), pulses/sessions ( B ), and RMT ( C ) in patients with poststroke aphasia treated with rTMS when rTMS is grouped by stimulation parameter and location

rTMS therapy is based on the theory of "hemispheric balance”, which states that under normal physiological conditions, the left and right hemispheres of the human brain are in a state of dynamic balance [ 21 ]. The dominant hemisphere of the brain governs language function; in healthy right-handed (and most left-handed) individuals, the left hemisphere is the dominant language hemisphere. Therefore, damage to different parts of the dominant hemisphere can result in various types of aphasia. Motor aphasia occurs most commonly in patients with damage to the frontal gyrus (oral expression center), whereas sensory aphasia occurs in patients with damage to the temporal gyrus (auditory comprehension center). Currently, motor aphasia is the predominant type of aphasia. Left hemisphere cortical excitability decreases in aphasic patients with damage to the dominant hemisphere, and increased excitability in the right hemisphere cortex further inhibits the left hemisphere, leading to decreased excitability in the damaged left hemisphere [ 22 ]. rTMS generates fast pulses of a certain frequency through a coil fixed onto the scalp, creating a rapidly changing magnetic field that acts on the target area and causes neuronal firing in the brain [ 53 ]. The duration of rTMS treatment is usually 10–30 min. High-frequency rTMS (HF-rTMS) (> 1 Hz) increases cortical excitability, whereas low-frequency rTMS (LF-rTMS) (≤ 1 Hz) decreases cortical excitability. rTMS has a better local therapeutic effect, and this effect persists for several months after cessation of treatment [ 19 , 54 ].

A recent literature review reported that LF-rTMS and HF-rTMS may be relatively effective and safe for the treatment of PSA, with LF-rTMS playing a mainly short-term role in subacute PSA, and HF-rTMS being the most effective in improving language function in the poststroke period. More severe lesion damage in patients is associated with better HF-rTMS effects [ 55 ]. However, no studies have been performed thus far to assess variables such as total pulses, pulses/session, and the value of RMT for achieving an optimal treatment effect of rTMS on PSA[ 55 ]. This is the first study to examine this question.

Most current studies have used LF-rTMS to stimulate the undamaged hemisphere, suppress its excitability, reduce corpus callosum inhibition, and enhance the excitability of the damaged hemisphere. Many systematic evaluation studies have assessed the efficacy of LF-rTMS and yielded better results [ 56 , 57 ]. For example, Sebastianelli et al. [ 56 ] evaluated whether LF-rTMS acting on the undamaged hemisphere positively affects language rehabilitation. Weiduschat et al. [ 57 ] utilized a randomized, controlled, double-blinded study design to divide 10 patients with nonfluent aphasia after subacute phase stroke into a true stimulation treatment group (six patients) and a sham stimulation control group (four patients). Stimulation of the right inferior frontal gyrus triangle was performed in the true stimulation treatment group and stimulation of unrelated brain regions at the top of the head was performed in the sham stimulation control group. The results showed that the language function of the true stimulation treatment group improved significantly after treatment compared to the pre-treatment period, with no significant improvement detected in the sham stimulation control group.

Moreover, positron emission computed tomography (PET) revealed a shift in metabolic activity to the right hemisphere during language tasks in the sham-stimulated control group but not in the true-stimulated treatment group. A randomized controlled double-anonymized trial found significant improvements in language function in 12 patients with subacute-phase aphasia who received 14 days of 1 Hz rTMS and speech training in the right hemisphere inferior frontal gyrus, with repetition and comprehension achieving moderate effects and naming achieving smaller effects [ 58 ]. Khedr et al. [ 59 ] recruited 15 patients with subacute phase aphasia and applied 1 Hz rTMS to the right subfrontal gyrus of the patients and 20 Hz rTMS to the left subfrontal gyrus and found a significant improvement in speech scores after 10 days and 2 months of intervention.

Hu et al. [ 23 ] compared the effectiveness of various rTMSfrequencies in individuals diagnosed with aphasia. The researchers randomly assigned the participants to one of four groups: high-frequency (10 Hz), low-frequency (1 Hz), sham stimulation, and control. All participants were administered a conventional treatment protocol, which included medication and frequent speech training. In the high-frequency group, stimulation was applied to the left hemisphere speech area, whereas in the low-frequency group, stimulation was targeted to the right hemisphere speech area. The results of the assessments conducted using the language scale immediately after the intervention and two months later indicated noteworthy enhancements in spontaneous speech, auditory comprehension, and aphasia quotients among participants in the low-frequency group compared to those in the high-frequency group. Nevertheless, the group exposed to high-frequency stimuli exhibited notable enhancements in repetition and aphasia quotients compared to the control group, particularly at the 2-month mark following the intervention, suggesting that LF-rTMS and HF-rTMS are beneficial for the recovery of language function in patients with aphasia, but that LF-rTMS produces both short-term and long-term benefits.

In contrast, HF-rTMS alone produces long-term benefits, and the benefits accrued through LF-rTMS appear more significant. The variables that contribute to the optimal treatment effect of LF-rTMS-RIFG, such as total pulse, pulse/session, and RMT values, have not been explored. When grouped by rTMS stimulation parameters and location, our nonlinear results showed that the best treatment effect was achieved when the total LF-rTMS-RIFG pulse was 40,000 (SMD:1.76, 95% CrI 0.36–3.29) and the pulse/session was 1000 (SMD:1.06, 95% CrI 0.54–1.59).

To study the mechanism of action of rTMS, Thiel et al. [ 47 ] conducted LF-rTMS in patients with aphasia and found that rTMS inhibited the adverse activation of the right cerebral hemisphere, leading to weakened inhibition of language-related regions of the left cerebral hemisphere and promoting the rebalancing of the bilateral cerebral hemispheres, thus improving the language function of patients with aphasia. Most studies have used unilateral hemispheric stimulation, and only a few have used bilateral hemispheric stimulation. In 2014, Khedr et al. [ 60 ] performed the first clinical study involving bilateral hemisphere stimulation, in which subjects were randomly divided into 2 groups: a bilateral hemisphere Broca's area stimulation group (experimental group) and a sham stimulation group. The results showed that the patients in the experimental group experienced significant improvements in language function compared to those in the control group. Vuk-Sanov et al. [ 61 ] divided subjects into a bilateral rTMS group and a unilateral rTMS group (control group), with bilateral rTMS being more effective in promoting the recovery of language function in patients with aphasia. In the present study, when rTMS was not grouped by stimulation parameters and location, our nonlinear results showed that the best results were obtained when the total pulse was 40,000 (SMD:1.86, 95% CrI 0.50 to 3.33), pulse/session was 1,000 (SMD:1.05, 95% CrI 0.55–1.57), and RMT was 80% (SMD:1.08, 95% CrI 0.60–1.57), which was also applied to patients with bilateral rTMS.

In 2005, Winhuise et al. [ 62 ] administered HF-rTMS at 4 Hz to the right inferior frontal gyrus of patients with aphasia after subacute left-sided cerebral infarction. The results suggest that patients treated with HF-rTMS showed higher activation in the right inferior frontal gyrus and had lower language abilities than those with aphasia who did not receive HF-rTMS when assessed for relevant language tasks. In a subsequent study, Szaflarski et al. [ 63 ] treated eight patients with chronic aphasia with an iTBS stimulation pattern in the left speech area with HF-rTMS (50 Hz) 5 days per week and observed that language function was restored. Nevertheless, recent research has indicated that HF-rTMS targeting the non-dominant hemisphere can be a viable therapeutic approach for enhancing language abilities in patients with PSA, particularly when the extent of the brain lesion is large. In another study, five patients with aphasia after massive cerebral infarction in the left cerebral hemisphere were randomized to three stimulation patterns of high-frequency (10 Hz), low-frequency (1 Hz), and sham stimulation in the right inferior frontal gyrus, each at an interval of 6 days, and were assessed using a picture-naming task that was performed immediately before and after each rTMS treatment. HF-rTMS treatment significantly improved naming ability compared with LF-rTMS and sham stimulation treatments [ 55 ].

Currently, there is a lack of research investigating the impact of total pulses, pulses per session, and RMT values on the optimal therapeutic outcome of HF rTMS for the treatment of PSA. In our study, when rTMS was not grouped by stimulation parameter and location, our nonlinear results showed that the best results were obtained when the total pulse was 40,000 (SMD:1.86, 95% CrI 0.50 to 3.33); pulse/session was 1000 (SMD:1.05, 95% CrI 0.55–1.57), and RMT was 80% (SMD:1.08, 95% CrI 0.60–1.57). It is hypothesized that these variables are also appropriate for patients with aphasia treated with HF-rTMS; however, the results must be further validated.

Limitations and strengths

Strengths : This study provides evidence for selecting the optimal pulse, pulse/session, and RMT for rTMS in PSA.

Limitations : Case studies and clinical trials differ in sample selection (e.g., lesion size/site), stimulation pattern, frequency of stimulation, and site of stimulation, which may bias the study results. Recently, there has been a growing tendency to highlight the importance of tailored TMS and, in general, multimodal (integrating noninvasive brain stimulation with other approaches such as cognitive training and physical exercise) rehabilitation programs. In addition, the heterogeneous nature of samples with post-infarction aphasia (as the characteristics and spread of the damaged area are unique to each patient) renders the advice of tailored TMS and cognitive rehabilitation protocols even more important. As a treatment, 1000 pulses per session may be delivered by employing numerous different protocols, which would have very different effects (for instance, at a low frequency, at a high frequency, using intermittent or continuous theta bursts). Therefore, additional prospective cohort studies and randomized controlled trials are required to enhance the existing body of evidence and demonstrate a definitive causal relationship.

The results of the meta-analysis of the stimulus-specific variables affecting the effect of rTMS on total symptoms in patients with PSA found that only total pulse correlated significantly with treatment outcome. LF-rTMS and HF-rTMS have been used to improve language function in patients with PSA. rTMS for PSA was most effective when the total pulse was 40,000, pulse/session was 1000, and RMT was 80%. This meta-analysis of clinical outcomes and selection of rTMS parameters for post-infarction aphasia provides a basis for evidence-based medical decisions regarding PSA. High-quality, randomized, controlled clinical studies with large sample sizes are needed to explore the stimulation parameters and sites for different stroke lesion/injury sites and aphasia types, which will improve the quality of clinical studies and provide more reliable evidence for rTMS in post-infarction aphasia.

Availability of data and materials

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

Abbreviations

  • Repetitive transcranial magnetic stimulation

Poststroke aphasia

Credible interval

Aphasia quotient

Aachen Aphasia Test

Boston Diagnostic Aphasia Examination

The Chinese Rehabilitation Research Center aphasia examination

Aphasia Severity Rating Scale

The Concise Chinese Aphasia Test

Right inferior frontal gyrus

Dual inferior frontal gyrus

Right temporoparietal region

Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Network Meta-Analyses

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Acknowledgements

The authors wish to thank ProfessorXin-ya Duan, Tuberculosis Department, The Third People's Hospital of Kunming City, Kunming, China, for sharing their expertise that greatly assisted the search and for revising comments that markedly improved the manuscript.

This work was supported by the Major Science and Technology Special Project of Yunnan Province under Grant [NO.202102AA100061], Nature Science Foundation of China under Grants [No. 82060252] and [No. 81960350], Yunnan Basic Research Projects under Grant [No. 2018FB115], Yunnan Health Training Project of High-level Talents under Grant [No. H-2018058], and Yunnan Applied Basic Research Project-Union Foundation of Chinaunder Grant [No. 202201AY070001-091].

Author information

Yang Tan, Lin-Ming Zhang and Xing-ling Liang contributed equally to this work.

Authors and Affiliations

Department of Emergency, The First Affiliated Hospital of Kunming Medical University, 295 Xichang Road, Wuhua District, Kunming, 650032, Yunnan, China

Yang Tan, Xing-ling Liang, Guei-fei Xiong, Xuan-lin Xing, Qiu-juan Zhang, Bing-ran Zhang, Zi-bin Yang & Ming-wei Liu

Department of Neurology, The First Affiliated Hospital of Kunming Medical University, Kunming, 650032, Yunnan, China

Lin-Ming Zhang

Department of Orthopedics, People’s Hospital of Dali Bai Autonomous Prefecture, Dali, 671000, Yunnan, China

Zi-bin Yang

Department of Emergency , People’s Hospital of Haimen District, Nantong, 226000, Jiangsu, China

Ming-wei Liu

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XX, GX, XL, LZ, YT, QZ, BZ, ZY, and ML contributed to data acquisition and analysis. YQ and YX contributed to data interpretation. XX, GX, XL, LZ, and YT contributed to the conception and design of the study, and drafted the manuscript. ZY and ML contributed to study design and drafted the manuscript. YX and ZY prepared Figs. 1 – 3 . XX, GX, XL, LZ, YT, QZ, BZ, ZY, and ML confirmed the authenticity of the raw data. All authors have read and approved the final manuscript.

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Tan, Y., Zhang, LM., Liang, Xl. et al. A literature review and meta-analysis of the optimal factors study of repetitive transcranial magnetic stimulation in post-infarction aphasia. Eur J Med Res 29 , 18 (2024). https://doi.org/10.1186/s40001-023-01525-5

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Complication rates and safety of pulsed dye laser treatment for port-wine stain: a systematic review and meta-analysis

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  • Published: 23 December 2023
  • Volume 39 , article number  16 , ( 2024 )
  • Meng dong Shi 1 ,
  • Kun Yang 1 ,
  • Shu bo Li 2 ,
  • Qian Zhao 3 ,
  • Ran Huo 1 , 3 &
  • Cong Fu 3  

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Pulsed dye laser (PDL) is the most commonly used method for port-wine stain (PWS); however, no studies have reported the safety of PDL. This review aimed to collect and summarize complications reported in relevant literature, assess complication rates in treating PWS with PDL, and explore the relevant influencing factors. A systematic review and meta-analysis were conducted to search for related studies in PubMed, Embase, and the Cochrane Library until August 2022. Two reviewers independently evaluated the risk of bias of included studies. Stata Software version 17.0 was used for the analysis. All complications reported in the literature are divided into acute phase complications and long-term complications. Overall pooled purpura, edema, crusting, blistering, hyperpigmentation, hypopigmentation, and scarring rates were 98.3%, 97.6%, 21.5%, 8.7%, 12.8%, 0.9%, and 0.2%, respectively. Although the acute adverse reactions were found to be common, the long-term permanent complications clearly have a lower frequency, and the occurrence of scarring is much lower than that initially thought. This indicates that effective protective measures after treatment are very important for preventing scar formation. Overall, PDL treatment for PWS shows a high level of safety and low chances of causing long-term complications.

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comparison and literature review

Data availability

The data used in the manuscript are extracted from the published articles (primary studies). All such primary studies are cited in the manuscript with complete reference provided in the reference list. The data extracted are summarized in the tables, figures and supporting information included in the manuscript.

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Department of Burn and Plastic Surgery, Shandong Provincial Hospital, Shandong University, No. 324, Jing Wu Road, Jinan, 250021, China

Meng dong Shi, Kun Yang & Ran Huo

Department of Burn and Plastic Surgery, The People’s Hospital Of Huaiyin Jinan, Jinan, China

Department of Burn and Plastic Surgery, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China

Qian Zhao, Ran Huo & Cong Fu

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Shi, M.d., Yang, K., Li, S.b. et al. Complication rates and safety of pulsed dye laser treatment for port-wine stain: a systematic review and meta-analysis. Lasers Med Sci 39 , 16 (2024). https://doi.org/10.1007/s10103-023-03961-5

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DOI : https://doi.org/10.1007/s10103-023-03961-5

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A comparison between antibiotic utilisation in public and private community healthcare in Malaysia

  • Audrey Huili Lim   ORCID: orcid.org/0000-0001-6721-1505 1 ,
  • Norazida Ab Rahman   ORCID: orcid.org/0000-0003-3969-1745 1 ,
  • Siti Nur Su’aidah Nasarudin 2 ,
  • Tineshwaran Velvanathan 2 ,
  • Mary Chok Chiew Fong 2 ,
  • Abdul Haniff Mohamad Yahaya 2 &
  • Sheamini Sivasampu   ORCID: orcid.org/0000-0003-2314-6048 1  

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There are two parallel systems in Malaysian primary healthcare services: government funded public primary care and privately-owned practices. While there have been several studies evaluating antibiotic utilisation in Malaysian public healthcare, there is a lack of literature on the use of antibiotics in the private sector. There is a dire need to evaluate the more recent performance of public vs. private community healthcare in Malaysia. As such, this study aimed at measuring and comparing the utilisation of antibiotics in the public and private community healthcare sectors of Malaysia in 2018–2021.

This study was a retrospective analysis of antibiotic utilisation in Malaysian primary care for the period of 1 January 2018 until 31 December 2021 using the nationwide pharmaceutical procurement and sales data from public and private health sectors. Rates of antibiotic utilisation were reported as Defined Daily Doses per 1000 inhabitants per day (DID) and stratified by antibiotic classes. The secondary analysis included proportions of AWaRe antibiotic category use for each sector and proportion of antibiotic utilisation for both sectors.

The overall national antibiotic utilisation for 2018 was 6.14 DID, increasing slightly to 6.56 DID in 2019, before decreasing to 4.54 DID in 2020 and 4.17 DID in 2021. Private primary care antibiotic utilisation was almost ten times higher than in public primary care in 2021. The public sector had fewer (four) antibiotic molecules constituting 90% of the total antibiotic utilisation as compared to the private sector (eight). Use of Access antibiotics in the public sector was consistently above 90%, while use of Access category antibiotics by the private sector ranged from 64.2 to 68.3%. Although use of Watch antibiotics in the private sector decreased over the years, the use of Reserve and ‘Not Recommended’ antibiotics increased slightly over the years.

Antibiotic consumption in the private community healthcare sector in Malaysia is much higher than in the public sector. These findings highlight the need for more rigorous interventions targeting both private prescribers and the public with improvement strategies focusing on reducing inappropriate and unnecessary prescribing.

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Introduction

Antibiotics are the most commonly prescribed drugs worldwide [ 1 , 2 ]. The extensive utilization of antibiotics is believed to have prolonged the average lifespan by two decades, causing a shift in the focus of diseases from communicable to non-communicable ones. The global public health challenge of antimicrobial resistance has been exacerbated by the excessive usage of antibiotics worldwide. Overprescription of antibiotics is linked to a higher risk of adverse effects, more frequent revisits to healthcare facilities, and the unnecessary medicalization of self-limiting conditions. The overprescription of antibiotics is particularly prevalent in primary care, where viral infections are the primary cause of most illnesses [ 3 , 4 ].

The World Health Organization (WHO) Expert Committee on Selection and Used of Essential Medicines developed the AWaRe Classification of antibiotics in 2017 as a tool to support antibiotic stewardship efforts at local, national, and global levels. The AWaRe classification categorizes antibiotics into three groups: Access, Watch, and Reserve, and emphasizes the importance of appropriate antibiotics use by taking into consideration the impact of different antibiotics and antibiotic classes on antimicrobial resistance. The Access group consists of first and second choices of empirical treatment of the most common infections. The Watch group antibiotics are indicated for a few, specific infectious conditions as they are more susceptible to antibiotic resistance and/or have higher toxicity concern. The Reserve group antibiotics are the “last resort” for highly selected patients (e.g. those with serious or life-threatening infections due to multidrug resistant bacteria) and require close monitoring [ 5 , 6 ].

In order to promote responsible use of antibiotics, evidence shows that at least 60% of national antibiotic consumption should consists of Access antibiotics for not only judicious use of antibiotics, but also reduced costs and increased access. One of the health-related targets of the sustainable development goals includes a target to achieve this threshold by 2023 [ 7 ].

Malaysia has a dual healthcare system with parallel public and private primary care health sectors [ 7 ]. The primary care level functions as the first point of contact care in a community setting [ 8 ]. A public clinic is usually staffed with doctors, nurses, pharmacists, and some other professions such as dietitians or physiotherapists, while the workforce of private clinics mainly consists of doctors and non-certified nursing aides where approximately 75% of these clinics are solo practices [ 9 ]. Federal revenue and taxation fund healthcare in the public sector while the private sector is funded mainly through out-of-pocket payments from patients, private health insurance and employee health benefits schemes. Private primary healthcare is mainly concentrated in the urban, affluent areas, focusing on acute conditions and curative care. Malaysia has yet to implement dispensing separation in the private sector; therefore, antibiotics can be prescribed and dispensed directly from doctors in the private clinics [ 10 , 11 ]. Antibiotics can only be purchased from retail pharmacies with a valid prescription. Although treatment guidelines for the management of infectious diseases or antibiotic treatment in primary care settings is available to provide recommendations for reasonable antibiotic usage, guideline adoption varies across practices in Malaysia [ 12 ]. In addition, the Ministry of Health (MOH) Malaysia has initiated a local antimicrobial stewardship (AMS) program for implementation at hospitals and primary care to encourage stewardship activities in all healthcare facilities in Malaysia [ 13 ].

There is a need to evaluate the more recent data on overall antibiotic use in primary care facilities in Malaysia to understand the utilisation pattern and for enhancement of AMS initiative. Furthermore, there remains a lack of data particularly with respect to the use of AWaRe classification to assess the antibiotics utilisation in public and private primary care facilities. As such, this study aimed at measuring patterns of antibiotic utilisation in public and private sector at primary care level for the period 2018–2021.

This study was reported in accordance to the STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) checklist (Supplementary Table S1 ).

Study design and setting

This study was a retrospective analysis of aggregated sales data of antibiotics for primary care facilities in Malaysia for the period 2018–2021. This study used the national drug procurement data obtained from the database of the Pharmaceutical Services Programme, Ministry of Health Malaysia. The database includes medicine purchasing records of all government health facilities throughout Malaysia. Detailed information about the database is described elsewhere [ 14 ]. Data on private sector procurement was derived from sales data which represents approximately two-third of the total pharmaceutical market coverage in Malaysia. As antibiotics prescribed in private clinics can also be purchased in retail pharmacies, sales data for retail pharmacies (private sector) were also collected. Detailed description of the data source is described elsewhere [ 15 ]. The public primary care is comprised of over 1000 public health clinics nationwide whereas the private sector includes nearly 8000 private clinics (general practitioners) that provide outpatient care and approximately 3000 retail community pharmacies [ 16 , 17 ]. Data on population size was obtained from the Department of Statistics Malaysia, based on the yearly population estimates of Malaysia [ 18 ].

Antibiotics

Data on antibiotics was retrieved according to the 2020 WHO Anatomical Therapeutic Chemical (ATC) Classification System [ 17 ]. All antibiotics for systemic use (code: J01) were identified and grouped by antibiotic classes. A total of 14 antibiotic classes (aminoglycosides, amphenicols, carbapenems, cephaloporins, fluoroquinolones, glycopeptides, macrolides, nitrofurans, nitroimidazoles, penicillins, steroids, sulfonamides, tetracyclines, and others) and 76 antibiotic molecules were included in this study.

Antibiotics were also classified into the AWaRe categories: Access, Watch, Reserve, and Not Recommended.

Statistical analysis

Data were converted into defined daily doses (DDDs) using the 2020 WHO ATC/DDD index. Antibiotic utilisation rates were calculated from the total DDD divided by the population and reported as DDD per 1000 inhabitants per day (DID) (Eq.  1 ) [ 18 ]. Percentage of antibiotics by antibiotic classes and AWaRe categories were calculated as utilisation per categories divided by total utilisation. Sensitivity analysis was performed by analysing data from private clinics only for antibiotic utilisation in the private sector. R version 4.1.0 was used to conduct data cleaning and analysis.

In 2021, total antibiotics utilisation for primary care in Malaysia was 4.17 DIDs. The antibiotics utilisation rate in private sector was higher at 3.78 DIDs compared to public sector (0.39 DIDs). Between 2018 and 2021, both sectors had declines in the antibiotic utilisation rate. The utilisation rate in the public sector decreased by 61.4% (from 1.01 to 0.39 DIDs) while in private sector it decreased by 26.3% (from 5.13 to 3.78 DIDs). The trend in antibiotic utilisation rates between 2018 and 2021 are shown in Fig.  1 by quarterly periods. The utilisation of antibiotics fell substantially in May-August 2020 as compared with the earlier period of January 2018-April 2020. The rate started to increase again in 2021. The private sector accounted for at least 80% of the total antibiotic utilisation in primary care, with the ratio remaining stable over the four years.

figure 1

Overall trend of antibiotic utilisation in public and private sector during 2018-2021

Distribution of antibiotic classes used in public and private sector are described in the percentage of all antibiotics (Fig.  2 ). Penicillins had the highest usage, accounting for 81% of antibiotics in public and 37% in private. Cephalosporins, macrolides, and tetracyclines took up a fair share of usage in the private sector, ranging between 15 and 41% of all antibiotics. The proportions of the use of these three classes in the public sector was much lesser than that in private. Figure  3 describes the trend in utilisation rates in DIDs for the five antibiotic classes used in both sectors: penicillins, macrolides, cephalosporins, sulfonamides, and tetracyclines. Utilisation of most antibiotics showed a decreasing trend between 2018 and 2021 for both public and private sectors, except for tetracyclines (75% increase in public and 20% increase in private) and cephalosporins (16% increase in public) (Fig.  3 , Supplementary Table S2 ). Four antibiotic molecules constituted 90% of the total antibiotic utilisation (Drug Utilisation 90, DU90%) in the public sector while 8 antibiotic molecules constituted DU90% of antibiotics in the private sector (Supplementary Table S3 ).

figure 2

Antibiotic classes used in public and private sector by share of DDDs during 2018-2021

figure 3

Trends of antibiotic utilisation in public and private sector during 2018–2021 for ( a ) penicillins; ( b ) macrolides; ( c ) cephalosporins; ( d ) sulfonamides; ( e ) tetracyclines

In the public sector, antibiotics from the Access group consistently accounted for at least 90% of the total antibiotics used (Fig.  4 ). The remaining proportion of antibiotics in the public sector was from the Watch category. For the private sector, the Access group antibiotics contributed 63–68% of the total antibiotics used during the period from 2018 to 2021. The Watch group antibiotics contributed one-third and there was minute use of antibiotics from the Reserve group (< 0.01%).

figure 4

Proportions of different AWaRe categories of antibiotics for public and private sectors during 2018-2021

We compared antibiotic utilisation by type of primary care facilities. All primary care facilities in the public sector are clinics while private sector comprised of clinics and community pharmacies. Within the private sector, clinics accounted for approximately 80% of total antibiotic utilisation whereas pharmacies constituted 20% (Supplementary Table S4 ).

Sensitivity analysis showed that proportion of Access category antibiotics used in the private sector decreased slightly when only sales data from private clinics were included (62–65% compared to 63–68%). There were no changes in the antibiotic molecules that constituted DU90. However, there was a small difference in the distribution of classes, with macrolides forming a greater proportion of use compared to tetracyclines (Supplementary Figure S1 ).

This study provides the most recent and comprehensive estimates on systemic antibiotic use at the primary care level in Malaysia for the public and private sectors. While earlier studies may have described antibiotic utilisation in various small-scale settings within the Asian region, to our knowledge, none have used the WHO AWaRe classification to assess and compare antibiotic utilisation between public and private facilities. In this study, we quantified changes in antibiotic utilisation rates over a four-year period from 2018 to 2021 and compared antibiotic use patterns using the DDD metrics and AWaRe classification.

We observed a reduction in overall antibiotic use across the primary care facilities in Malaysia during the study period. The decreasing trend of antibiotic utilisation rates in both sectors is encouraging, but the decline was likely driven by the COVID-19 pandemic. A substantial reduction was seen particularly in 2020 which coincides with the time of the national lockdown and restrictions implemented in Malaysia due to COVID-19 which began in March 2020 [ 20 ]. Movement restrictions and COVID-19 concerns led to fewer patients seeking care at primary care facilities and reduced frequency of infectious disease or influenza-like illnesses, which may have affected the use of antibiotics during this period. The reduction in antibiotic utilisation during the pandemic period was seen in both public and private sectors, reflecting reduced overall stream of patients. Yang et al. also reported a decrease in antibiotic utilisation from an analysis of China’s national procurement data due to the COVID-19 pandemic [ 19 ]. In Japan, there was a 20% decrease in antimicrobial consumption in 2020 compared to the preceding year [ 20 ]. Similar findings were observed in Scotland and Canada by Malcolm et al. and Knight et al. [ 21 , 22 ], while Nandi et al. reported that the global sales of four antibiotic group decreased in April and May 2020 compared to the pre-pandemic period [ 6 ].

The global goal of WHO is to have at least 60% share of antibiotics from the Access group [ 23 ]. Our findings showed that in primary care, both public and private sectors achieved this target. For the public sector in Malaysia, utilisation of antibiotics is restricted by the MOH formulary that determines the type of antibiotic formulations that can be prescribed in the public health facilities [ 24 ]. The formulary not only serves as a reference for medicines used in public MOH facilities but also functions as a policy and administrative approach to regulate and encourage rational and quality use of medicines in all MOH institutions. Drugs are evaluated for functionality and cost effectiveness before being included in the formulary. There is a limited number of antibiotics available to prescribers in public primary care, none of which are on the Reserve list. This was also reflected in our findings in terms of number of antibiotic molecules that constituted DU90% when compared to those in the private sector. A substantial proportion of antibiotics from the Watch category was reported from the private sector which may warrant further monitoring in terms of utilisation rates and the appropriateness. The increase in consumption of Watch antibiotics which was observed in most countries in the recent years might reflect the market share of antibiotics and rates of resistant infections within the country [ 6 , 25 ]. Furthermore, implementation of the National Antibiotic Guidelines is stricter in the public sector while the practitioners in the private sector are at liberty to adopt whichever guidelines they see fit, be it from the local context or not. The national Antimicrobial Stewardship Programme (ASP) conducted by MOH is only currently enforced in government facilities. Private GPs are not subjected to the clinical and structural audits that are a part of the ASP.

The private sector accounted for a larger proportion of overall antibiotic use in primary care than the public sector in Malaysia. This finding echoes a previous cross-sectional study on antibiotic prescribing practice in primary care in Malaysia in 2014 [ 26 ]. The proportion of antibiotic utilisation in the private sector at the beginning of 2018 (six times higher than in public primary care clinics) was slightly lower than the results of a previous study in 2012 (seven times higher than in public primary care clinics) [ 27 ]. However, by the end of 2021, private primary care antibiotic utilisation was almost ten times higher than in public primary care, indicating an increasing trend in the proportion of antibiotic utilisation by the private sector. Higher antibiotic utilisation in the private sector is postulated to be due to a higher percentage of acute cases seen in private clinics [ 7 , 28 ]. Furthermore, patients are more likely to demand antibiotics in the private sector due to greater out-of-pocket payments. Prescribers are then more inclined to give in to patient demands to supply antibiotics unnecessarily [ 29 ]. Sensitivity analyses looking at antibiotic utilisation in private clinics only indicated there was not much change in the results, only seeing a slight decrease in proportion of Access category antibiotics used and macrolides comprising a greater proportion of private sector utilisation of antibiotics. This indicates that the types of antibiotics used in retail pharmacies is fairly similar to that in private clinics.

Antimicrobial surveillance steps in Malaysia begun in 2019 with the implementation of specific terms of references and clinical pathways for antibiotic use in primary care [ 12 ]. Infection control measures for public primary care facilities also included hand hygiene protocols and audits [ 30 ]. Though most of the initiatives were largely conducted in the public health sector, efforts are being made to expand the program coverage for implementation at private facilities. The stewardship program includes the formation of a multidisciplinary team to conduct surveillance and feedback activities on antimicrobial consumption. Given the current structure of private primary care practices in Malaysia, collaborative partnerships between general practitioners and community pharmacists are necessary to promote quality use of not only antibiotics, but medicines in general [ 31 , 32 , 33 ]. Lower antibiotic consumption as well as increased guideline-adherent prescribing have also been documented when pharmacists were involved in the process [ 34 , 35 , 36 , 37 ].

Limitations

Our study has limitations that need to be considered when interpreting the results. Data were only available from 2018, limiting analysis of earlier trends. We used aggregated procurement data for analysis which may not accurately reflect consumption of antibiotics. There may have been drugs procured but not utilised due to expiration or wastage. Data from private retail pharmacies might include antibiotics supplied for prescriptions from hospitals or veterinary purposes which we are not able to differentiate from this database. Finally, as the data are not available at individual patient-level, we are not able to study the appropriateness of antibiotics usage.

Implications for research and/or practice

Our study contributes data on antibiotics utilisation rate at primary health care facilities in Malaysia and provides a better understanding on patterns of antibiotic use between public and private sector. Future work to look into prescription level data will shed more light on the appropriateness of antibiotic utilisation and potential overuse or misuse of antibiotics. This will enable us to better understand and evaluate the trends in antibiotic use, for instance, the increasing use of aminoglycosides, of which two of the antibiotics in the class are on the Watch list. Compared to neighbouring countries such as Singapore and Myanmar, Malaysia’s national research agenda on antimicrobials is still in its infancy [ 30 ]. This includes a budget allocation for research or collaborative work. A national research agenda will identify and highlight focus research areas for the country in order to inform antibiotic guidelines and policy. Targets for reducing total antibiotic utilisation rates and inappropriate prescribing has to be applied to both public and private sector against the setting of antimicrobial resistance goals.

We described antibiotic usage across public and private primary care facilities in Malaysia over the period 2018–2021. We identified a substantial reduction in antibiotic utilisation rates, particularly during the COVID-19 pandemic period across both sectors. The patterns of antibiotic usage indicate greater variations in types of antibiotic molecules used in the private compared to the public sector. The WHO AWaRe classification provides a useful framework to measure antibiotic utilisation patterns and setting targets for antibiotic surveillance systems. Despite higher antibiotic utilisation rates noted in the private sector compared to their public counterparts, both sectors are in line with WHO’s target of at least 60% of antibiotic use consists of Access antibiotics. These findings highlight the need for more rigorous interventions, targeting both prescribers and the public. Improvement strategies should focus on reducing inappropriate and unnecessary prescribing.

Data availability

Data and materials used in this study is not publicly available but can be provided upon reasonable request from the corresponding author (Audrey Huili Lim, [email protected]).

Abbreviations

Defined Daily Doses

Defined Daily Doses per 1000 inhabitants

World Health Organisation

Ministry of Health Malaysia

Antimicrobial Stewardship

Anatomical Therapeutic Chemical

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Acknowledgements

The authors thank the Director General of Health Malaysia for his permission to publish this article.

The study did not receive any funding.

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Audrey Huili Lim, Norazida Ab Rahman & Sheamini Sivasampu

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Study design and conceptualization: AHL, NAR and SS. Data collection and interpretation: SNSN, TV, MCCF, and AHMY. Data cleaning and analyses: AHL. Preparation of first draft: AHL and NAR. Review and editing: SNSN, TV, MCCF, AHMY, and SS. All authors approved the final version of the manuscript.

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Lim, A.H., Ab Rahman, N., Nasarudin, S.N.S. et al. A comparison between antibiotic utilisation in public and private community healthcare in Malaysia. BMC Public Health 24 , 79 (2024). https://doi.org/10.1186/s12889-023-17579-3

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    This packet will also suggest a variety of organizational patterns for literature reviews and address some major revision concerns and methods for citing sources appropriately. Goals. 1. To help you understand the functional purpose and requirements of an effective literature review. 2. To help you critically assess research materials. 3.

  6. Ten Simple Rules for Writing a Literature Review

    Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications .For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively .Given such mountains of papers, scientists cannot be expected to examine in detail every ...

  7. Comparative Literature Review Essays

    A comparative review may, e.g., require you to examine two schools of thought, two issues, or the positions taken by two persons. You may create a hierarchy of issues and sub-issues to compare and contrast, as suggested by the following general plan. This model lists 3 options for structuring the body of the review. In all cases, you are expected to deal with the similarities (compare) and ...

  8. Evaluating Sources & Literature Reviews

    A good literature review evaluates a wide variety of sources (academic articles, scholarly books, government/NGO reports). It also evaluates literature reviews that study similar topics. This page offers you a list of resources and tips on how to evaluate the sources that you may use to write your review.

  9. Literature Review Overview

    A literature review discusses published information in a particular subject area. Often part of the introduction to an essay, research report or thesis, the literature review is literally a "re" view or "look again" at what has already been written about the topic, wherein the author analyzes a segment of a published body of knowledge through summary, classification, and comparison of prior ...

  10. Writing a Literature Review

    A literature review is an integrated analysis of scholarly writings that are related directly to your research question. Put simply, it's a critical evaluation of what's already been written on a particular topic.It represents the literature that provides background information on your topic and shows a connection between those writings and your research question.

  11. Literature Reviews

    "Literature review" done. Right? Wrong! The "literature" of a literature review refers to any collection of materials on a topic, not necessarily the great literary texts of the world. "Literature" could be anything from a set of government pamphlets on British colonial methods in Africa to scholarly articles on the treatment of a torn ACL.

  12. Writing a literature review

    Writing a literature review requires a range of skills to gather, sort, evaluate and summarise peer-reviewed published data into a relevant and informative unbiased narrative. Digital access to research papers, academic texts, review articles, reference databases and public data sets are all sources of information that are available to enrich ...

  13. Comparing and Contrasting in an Essay

    For example, a literature review involves comparing and contrasting different studies on your topic, and an argumentative essay may involve weighing up the pros and cons of different arguments. A faster, more affordable way to improve your paper

  14. How to Write 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.

  15. How do I compare and contrast theories and ideas in my literature

    How do I compare and contrast theories and ideas in my literature review or research paper? Mar 29, 2022 27981 You'll find a number of resources to help you with writing on our Writing Help guide. You may find it helpful to review the section of our Literature Review Tutorial that discusses synthesizing ideas.

  16. Comparing Integrative and Systematic Literature Reviews

    Table 1. Literature Review Articles in HRDR 2002-2021. Open in viewer Table 2 presents a comparison of integrative and systematic literature reviews.

  17. How to Write a Literature Review

    A literature review is much more than an annotated bibliography or a list of separate reviews of articles and books. It is a critical, analytical summary and synthesis of the current knowledge of a topic. ... Types of Literature Reviews. There are different types of literature reviews, and different purposes for writing a review, but the most ...

  18. Systematic and scoping reviews: A comparison and overview

    A systematic review is a formalized method to address a specific clinical question by analyzing the breadth of published literature while minimizing bias. Systematic reviews are designed to answer narrow clinical questions in the PICO (population, intervention, comparison, and outcome) format. Alternatively, scoping reviews use a similar ...

  19. 5. The Literature Review

    Definition 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.

  20. Systematic, Scoping, and Other Literature Reviews: Overview

    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.

  21. Systematic and scoping reviews: A comparison and overview

    Alternatively, scoping reviews use a similar systematic approach to a literature search in order to determine the breadth and depth of knowledge on a topic; to clarify definitions, concepts, and themes; or sometimes as a precursor to a systematic review or hypothesis generator to guide future research.

  22. Literature Review vs Systematic Review

    It's common to confuse systematic and literature reviews because both are used to provide a summary of the existent literature or research on a specific topic. Regardless of this commonality, both types of review vary significantly.

  23. 14 Types Of Literature Review

    4 Major Types Of Literature Review. The four major types include, Narrative Review, Systematic Review, Meta-Analysis, and Scoping Review. These are known as the major ones because they're like the "go-to" methods for researchers in academic and research circles.

  24. A literature review and meta-analysis of the optimal factors study of

    The existing literature indicates that repetitive transcranial magnetic stimulation (rTMS) can potentially enhance the prognosis of poststroke aphasia (PSA). Nevertheless, these investigations did not identify the most effective parameters or settings for achieving optimal treatment outcomes. This study involved a meta-analysis aimed to identify the optimal variables for rTMS in treating post ...

  25. Gun Control Agendas in Networked Digital Environment: An Intermedia

    Literature Review Gun Reform Movement: MFOL. ... The review process was inductive: Each member of the team read through the samples individually and discussed together to reach consensus that the number of distinctive topics should be in the range between 10 and 15. ... Since a simple comparison of correlation coefficients ignores synchronous ...

  26. Complication rates and safety of pulsed dye laser treatment ...

    Pulsed dye laser (PDL) is the most commonly used method for port-wine stain (PWS); however, no studies have reported the safety of PDL. This review aimed to collect and summarize complications reported in relevant literature, assess complication rates in treating PWS with PDL, and explore the relevant influencing factors. A systematic review and meta-analysis were conducted to search for ...

  27. A comparison between antibiotic utilisation in public and private

    There are two parallel systems in Malaysian primary healthcare services: government funded public primary care and privately-owned practices. While there have been several studies evaluating antibiotic utilisation in Malaysian public healthcare, there is a lack of literature on the use of antibiotics in the private sector. There is a dire need to evaluate the more recent performance of public ...

  28. 'Mansfield and Dirksen' Review: Why Can't We All Get Along?

    Reviews. Architecture Review. Art Reviews. Film Reviews. Television Reviews. ... Our 2023 Guide to the Best Gifts The 10 Best Books of 2023 Who Read What in 2023 'The Book at War' Review.

  29. Raging Grace review

    Sun 31 Dec 2023 06.00 EST. J oy (Max Eigenmann), an undocumented Filipina immigrant, is striving to secure a better life for her daughter Grace (an impish Jaeden Paige Boadilla) through a series ...