breath research

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• Published: 09 January 2023

Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials

• Guy William Fincham 1 ,
• Clara Strauss 1 , 2 ,
• Jesus Montero-Marin 3 , 4 , 5 &
• Kate Cavanagh 1 , 2  

Scientific Reports volume  13 , Article number:  432 ( 2023 ) Cite this article

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Deliberate control of the breath (breathwork) has recently received an unprecedented surge in public interest and breathing techniques have therapeutic potential to improve mental health. Our meta-analysis primarily aimed to evaluate the efficacy of breathwork through examining whether, and to what extent, breathwork interventions were associated with lower levels of self-reported/subjective stress compared to non-breathwork controls. We searched PsycInfo, PubMed, ProQuest, Scopus, Web of Science, ClinicalTrials.gov and ISRCTN up to February 2022, initially identifying 1325 results. The primary outcome self-reported/subjective stress included 12 randomised-controlled trials ( k  = 12) with a total of 785 adult participants. Most studies were deemed as being at moderate risk of bias. The random-effects analysis yielded a significant small-to-medium mean effect size, g  = − 0.35 [95% CI − 0.55, − 0.14], z  = 3.32, p  = 0.0009, showing breathwork was associated with lower levels of stress than control conditions. Heterogeneity was intermediate and approaching significance, χ 2 11  = 19, p  = 0.06, I 2  = 42%. Meta-analyses for secondary outcomes of self-reported/subjective anxiety ( k  = 20) and depressive symptoms ( k  = 18) showed similar significant effect sizes: g  = − 0.32, p  < 0.0001, and g  = − 0.40, p  < 0.0001, respectively. Heterogeneity was moderate and significant for both. Overall, results showed that breathwork may be effective for improving stress and mental health. However, we urge caution and advocate for nuanced research approaches with low risk-of-bias study designs to avoid a miscalibration between hype and evidence.

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Introduction

Breathwork comprises various practices which encompass regulating the way that one breathes, particularly in order to promote mental, emotional and physical health (Oxford English Dictionary) 1 . These techniques have emerged worldwide with complex historical roots from various traditions such as yoga (i.e., alternate nostril breathing) and Tibetan Buddhism (i.e., vase breathing) along with psychedelic communities (i.e., conscious connected breathing) and scientific/medical researchers and practitioners (i.e., coherent/resonant frequency breathing). Recently, breathwork has been garnering public attention and popularity in the West due to supposed beneficial effects on health and well-being 2 in addition to the breathing-related pathology of covid-19, however it has only been partly investigated by clinical research and psychiatric medical communities.

Slow-paced breathing practices have gained most research attention thus far. Several psychophysiological mechanisms of action are proposed to underpin such techniques: from polyvagal theory and interoception literature 3 along with enteroception, central nervous system effects, and increasing heart-rate variability (HRV) via modulation of the autonomic nervous system (ANS) and increased parasympathetic activity 4 . ANS activity can be measured using HRV, the oscillations in heart rate connected to breathing (i.e., the fluctuation in the interval between successive heart beats) 5 . Fundamentally, as one inhales and exhales, heart rate increases and decreases, respectively. Higher HRV, arising from respiratory sinus arrhythmia 6 , is typically beneficial as it translates into robust responses to changes in breathing and thus a more resilient stress-response system 7 .

Stress-response dysfunction, associated with impaired ANS activity, and low HRV are common in stress, anxiety, and depression 8 , 9 , 10 , 11 , 12 . This may explain why techniques like HRV biofeedback can be helpful 13 , however, it is possible that simply pacing respiration slowly at approximately 5–6 breaths/minute, requiring no monitoring equipment, can elicit similar effects 14 . Polyvagal Theory 3 , for instance, posits that vagal nerves are major channels for bidirectional communication between body and brain. Bodily feedback has profound effects on mental states as 80% of vagus nerve fibres transmit messages from body to brain 15 . Further, the neurovisceral integration model states that high vagal tone is associated with improved health along with emotional and cognitive functioning 16 , 17 . Vagal nerves form the main pathway of the parasympathetic nervous system, and high HRV indicates greater parasympathetic activity 7 .

Modifying breathing alters communication sent from the respiratory system, rapidly influencing brain regions regulating behaviour, thought and emotion 18 . Likewise, respiration may entrain brain electrical activity 19 , with slow breathing resulting in synchrony of brain waves 20 , thereby enabling diverse brain regions to communicate more effectively 21 . It has been observed that adept long-term Buddhist meditation practitioners can achieve states where brain waves are synchronised continuously 22 .

Breathwork and stress

Stress, anxiety and depression have markedly exceeded pre-covid-19 pandemic population norms 23 . Thus, research is needed to address how this can be mitigated 24 . A recent survey based on more than 150,000 interviews in over 100 countries suggested that 40% of adults had experienced stress the day preceding the survey (Gallup, US) 25 . Prior to the pandemic, mental health difficulties were already a significant issue. For instance, stress has been identified by the World Health Organisation as contributing to several non-communicable diseases 26 and a 2014 survey, led in collaboration with Harvard, of over 115 million adults showed that 72% and 60% frequently experienced financial and occupational stress, respectively (Robert Wood Johnson Foundation, US) 27 .

Chronic stress is associated with, and can significantly contribute to, many physical and mental health conditions, from hypertension and cardiovascular disease to anxiety and depression 28 . For common mental health problems such as anxiety and depression, cognitive behavioural therapy (CBT) is widely recommended in treatment guidelines worldwide 29 , 30 , yet many do not recover and waiting times can be long 31 , 32 , in addition to extensive professional training and ongoing supervision being required for therapists. Moreover, such treatment is typically individualised and offered on a one-to-one basis making it resource intensive. The present state of global mental health coupled with the access barriers to psychological therapies requires interventions that are easily accessible and scalable 7 , and manualised practices such as breathwork may meet this remit.

Breathing exercises can be easily taught to both trainers and practitioners, and learned in group settings, increasingly via synchronous and asynchronous methods remotely/online. Therefore, given the need for effective treatments that can be offered at scale with limited resources, interventions focusing on deliberately changing breathing might have significant potential. Indeed, some government public health platforms already recommend deep breathing for stress, anxiety and panic symptoms (NHS and IAPT, UK) 33 , 34 . However, the evidence underlying this recommendation has not been scrutinised in a comprehensive systematic review and meta-analysis and this is the aim of the current study.

Moreover, it is not only slow-paced breathing which may help reduce stress. Fast-paced breathwork may also offer therapeutic benefit as temporary voluntarily induced stress is also known to be beneficial for health and stress resilience. For example, regular physical exercise can improve stress, anxiety and depression levels 35 , along with HRV 36 . Similarly, fast-paced breathing techniques can induce short-term stress that may improve mental health 37 , and have also been shown to volitionally influence the ANS, promoting sympathetic activity 38 . There are countless breathwork techniques—and such variation in their potential modalities and underlying principles warrants exploration.

Review aims

It is important that hype around breathwork is grounded in evidence for efficacy—and effects are not overstated to the public. Whilst some previous reviews of breathwork have been published, it is not possible to conclude the effectiveness of breathwork for stress (nor mental health in general) based on previous meta-analyses, since they have been restricted by certain factors. These include focusing on populations with impaired breathing (i.e., chronic obstructive pulmonary disease—COPD, and Asthma) 39 , 40 , insufficient focus on the breathwork intervention itself (i.e., including interventions where breathwork is combined with several other intervention components) 41 making it hard to elicit separate effects, along with spanning more literature on self-reported/subjective anxiety and depression compared to stress 14 . On the other hand, systematic reviews with narrative syntheses of quantitative data may have overlooked key studies because of too much focus on a specific technique (i.e., slow breathing or diaphragmatic breathing) 4 , 42 , an absence of randomised-controlled trials (RCTs), scanter literature on self-reported/subjective stress compared to self-reported/subjective symptoms of anxiety and depression, along with limited databases 4 , or exclusion of unpublished studies and grey literature (i.e., theses/dissertations) 43 .

Furthermore, in keeping with the participant, intervention, control, outcome and study design (PICOS) framework 44 , there is an absence of examining dose–response correlates with effects and subgroup analyses evaluating differential effects of different breathwork interventions and how they were delivered, what controls were used, effects on populations with differing health statuses and, finally, the psychological outcome measures used. All of these are crucial for an adequate ethical, precautional and practical implementation of breathwork interventions. Accordingly, subgroup analyses were explored to account for these, for the primary outcome of stress. It could be relevant to investigate potential sources of heterogeneity in terms of effects on stress, and this might be related to how some subgroups (such as mental/physical health populations, along with nonclinical/general populations) receive the intervention. Moreover, other subgroups such as the type of breathwork intervention (i.e., slow/fast) and how it is delivered (i.e., online/in-person or individual/group-based), along with the type of comparator (active/inactive control) and outcome measure (questionnaire) used to self-report on stress, may be sources of heterogeneity and thus warrant investigation.

So far, there is no existing meta-analysis of RCTs on the effect of breathwork on psychological stress. Thus, to fill this research gap, the aim of our meta-analysis was to estimate the effect of breathwork in targeting stress. Because prolonged stress can significantly contribute to anxiety and depressive symptoms and there is considerable overlap between them 45 , 46 , we included these two common mental health issues as secondary outcomes, to provide a bigger picture and greater context around the findings on stress. The primary outcome was pre-registered as stress since it is a transdiagnostic variable, relevant in a variety of disorders, and also in people without a diagnosis but suffering from high levels of psychological distress 47 . This makes stress a very interesting target for breathwork-based interventions.

In brief, our research question was the following: do breathwork interventions lead to lower self-reported/subjective stress (primary outcome), anxiety, and depression (secondary outcomes) in comparison to non-breathwork control conditions? We propose this work as a first comprehensive systematic review and meta-analysis exploring the effects of breathwork on stress and mental health, to help lay a solid foundation for the field to grow and evolve in an evidence-based manner.

We focused solely on RCTs reporting psychological measures, to gauge any potential efficacy or effectiveness of breathwork. We also explored sub-analyses for stress outcomes depending on the health status of the study population, technique, and delivery of breathwork, along with types of control groups and stress outcome measures used. Finally, we examined dose–response effects of breathwork on stress.

Pre-registration and search strategy

Our meta-analysis was pre-registered on the international prospective register of systematic reviews PROSPERO (2022 CRD42022296709). Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards were applied throughout. We searched published, unpublished, and grey literature in the following five databases: PsycInfo, PubMed, ProQuest, Scopus, and Web of Science, along with two clinical trial registers: ClinicalTrials.gov and ISRCTN. The search was run up to February 2022 for all seven electronic repositories, with no date restrictions, in line with the search criteria pre-registered on Prospero, including keywords such as: breath*, respir*, random*, RCT, and stress (see Online Appendix A for the detailed search). For purposes of feasibility in conducting the search, we maintained our focus on the pre-registered primary outcome, following Cochrane Collaboration guidelines to meet the highest criteria for self-reported/subjective stress outcomes by searching trial registers for unpublished studies. There is limited search functionality on trial registers and time involved in contacting researchers for trial data. Moreover, as mentioned above, some previous reviews have not searched unpublished, grey literature before and there are less data available on breathwork and self-reported/subjective stress, in comparison to self-reported/subjective anxiety and depression. In brief, given our focus on stress (paired with time and resource constraints), we conducted the most robust search possible for the primary outcome whilst secondary outcomes only included published data—and we were explicit about this from pre-registration onwards.

Inclusion and exclusion criteria

Inclusion criteria were that studies: (1) were published in the English language, (2) included a breathwork intervention where breathwork formed 50% or more of the intervention (and home practice/self-practice, if any), (3) were RCTs, (4) included an outcome measure of self-reported/subjective stress, anxiety, or depression, (5) included an adult participant sample 18 + years of age. For the five databases, studies with abstracts that did not include either the primary outcome keyword (stress), or a secondary outcome keyword (anxiety or depression), were excluded. For the two registers, if it was clear from the summary information that trials did not comprise the primary outcome of stress, they were excluded. As mentioned above, stress is a transdiagnostic health variable, relevant across various (clinical and nonclinical) populations and conditions, hence it was our primary interest. Additional rationale included the fact that there is far more limited research literature available on self-reported/subjective stress and breathwork (as opposed to anxiety and depression) and, since this was the primary outcome, because fewer (published) data were available, and to make the secondary search (which was only used in the present study to contextualise findings) more feasible, we used the referred search strategy, as this allowed us to find more information on stress from unpublished sources.

For all electronic repositories, studies with control conditions that comprised components of breathwork were excluded, except for studies which had time-points wherein data were collected before controls participated in breathwork (i.e., crossover RCTs). Only non-breathwork controls were used as post-intervention comparisons. Studies with interventions that comprised of equipment (oronasal or otherwise) which physically altered and/or assisted breathing activity were excluded. Breathwork was operationalised as techniques which involved conscious and volitional control or manipulation of one's breath (depth, pattern, speed or otherwise) through deliberate breathing practices. Interventions that affected breathing as a by-product, e.g., mindfulness, singing, and aerobic exercise, were excluded.

Review strategy and study selection

The first author conducted the search and initial screening against eligibility criteria along with full-text screening. Records were then screened, excluding reports based on review of titles and keywords in abstracts or summary information (for trials), or if the inclusion criteria were not met. Remaining reports were sought for retrieval and the full-text reports assessed for eligibility, before final eligibility decisions were made. Further identification of studies comprised forward and backward citation searching via Google Scholar and reference lists, respectively, of the final reports included from the database/registry search. For inter-rater consistency purposes, one of the authors (JMM) checked a random sample (10% of reports) after duplicates had been removed. Furthermore, where GWF was unsure after full-text screening, they consulted authors KC and CS to come to a collective decision on eligibility. Any discrepancies between authors were resolved by discussion and reaching consensus.

Data extraction

Our primary outcome was self-reported/subjective stress. Secondary outcomes were self-reported/subjective anxiety, depression, and global mental health (where two or more of stress, anxiety and depression were combined into a total measure without providing subscale data). We extracted the following data across the studies’ conditions: sample sizes, means, and standard deviations of outcome scores post-intervention (timepoint 1—T1, where T0 is pre-intervention/baseline) along with at latest follow-up where possible (a true follow-up was classed as when participants no longer received any instruction for the breathwork intervention). Where studies involved crossover designs, the midpoints were categorised as post-intervention (before the control group started the breathwork given initially to the intervention group). For studies which required multiple groups’ mean and standard deviation (M ± SD) scores to be combined, or for just SDs to be calculated, these were calculated in accordance with the Cochrane Collaboration handbook 48 . For example, calculating SDs from Ms and 95% confidence intervals (CIs) or combining multiple groups’ M ± SD scores if two or more groups completed an intervention that involved breathwork (but the study still comprised a non-breathwork control).

Risk of bias and quality assessment

The most recent, revised Cochrane Collaboration’s tool for assessing risk of bias in randomised trials (RoB 2) 49 was used for analysing studies on the primary outcome measure of self-reported/subjective stress. The studies were analysed across the following five domains for the stress outcomes: randomisation process, deviations from intended interventions, missing outcome data, measurement of the outcome, and selection of the reported result. Each domain produced an algorithmic judgement of “low risk of bias”, “some concerns”, or “high risk of bias”, resulting in an overall risk of bias judgement. For further inter-rater consistency purposes, both JMM and GWF completed bias scoring using RoB 2 on all included studies for stress, with any discrepancies resolved via discussion.

Data synthesis and analysis

To evaluate whether breathwork can effectively lower stress compared to non-breathwork controls and to quantify the estimation we ran a quantitative synthesis meta-analysis using standardised mean differences and a random-effects model. This used aggregate participant data of M ± SD scores on stress outcome measures for intervention and control conditions of each study at post-intervention (T1), along with the groups’ sample sizes. We also conducted a sensitivity analysis by removing one study at a time, to evaluate the robustness of effects. Separate random-effects meta-analyses were run for the secondary outcomes. The software Review Manager (RevMan) version 5.4 50 was used. For the between-group effect sizes (ESs) we computed Hedges’ g , based on the standardised between-group difference at post-intervention considering sampling variance among groups; an ES of 0.2 is classed as small, 0.5 medium and 0.8 large 51 . For each separate outcome, the ESs were calculated via comparison of post-breathwork intervention scores between the conditions. Intention-to-treat data were chosen over per-protocol data where available, since the former provides a more conservative estimate of between-group differences.

Heterogeneity of ESs variance was assessed using Cochran’s Q 52 based on a chi-square distribution ( χ 2 ) and Higgins’ I 2 53 . If χ 2 is significant and an I 2 index value is around 50%, this implies variance may be explained by variables other than breathwork and such statistical heterogeneity is moderate, respectively. A funnel plot was produced to examine publication bias for the primary outcome, and the software R (version 4) 54 was used to explore asymmetry of the funnel plot via the Egger’s test 55 (i.e., correlations between standard error and ESs). Moreover, Rosenthal’s fail-safe N was calculated (to estimate how many further studies yielding zero effect would be required to make the overall ES non-significant for stress) 56 . Kendall's tau-b (τ B ) correlations were used to detect any potential relationships between ESs of breathwork on stress and: estimated total duration of intervention/home practice, total number of intervention/home practice sessions, and intervention/home practice session frequency. If intervention time was not provided by a study (where participants only had home practice), we used the minimum estimated home practice duration (recommended in the study) to gauge the approximate time taken for participants to ‘learn’ the breathwork technique. Minimum recommended duration was used for most conservative estimates, helping account for common attrition found across behavioural studies.

Lastly, subgroup analyses were run for stress, again using a random-effects model. These subsets included: health status of population (physical, nonclinical, or mental health), technique type (fast or slow-paced breathing) and delivery method of the breathwork intervention (individual, group, or a combination of both, and remote (self-help), in-person, or combination) along with the type of control group (active or inactive; in line with Cochrane Collaboration guidelines 48 ), and outcome measure used (scale).

Search results

As shown in Fig.  1 , the search produced 1325 results: 1175 and 150 records from databases and registers, respectively. After duplicates were removed, the titles and abstracts (or summary information for registers) of 679 records were screened. During screening, the eligibility of 11% of reports were decided collectively among GWF, KC, and CS. All studies included by GWF were checked by KC and CS to ensure none were incorrectly included. One particular study 57 that comprised a global mental health measure only had to be excluded as there were insufficient studies to reliably interpret results ( n  < 5) 58 —the only other available was Goldstein et al. 59 (which also included a measure of self-reported/subjective stress). Accordingly, the global mental health secondary outcome was dropped from the analysis.

PRISMA flow diagram showing the identification of eligible studies via databases, registers, and citation searching. Self-reported/subjective stress was the primary outcome for the quantitative synthesis random-effects meta-analysis. Total number of included studies was 26. Trial registries searched primary outcome only.

Further data were required for eight reports; corresponding authors were contacted, and data from four studies were retrieved, but not the remaining half 60 , 61 , 62 , 63 subsequently excluded from the analysis. Thus, a total of 104 reports were screened and 81 were excluded, leaving 23. As a result of citation searching, a further three studies were included. Of the 26 total reports included in the quantitative synthesis meta-analyses, stress comprised 12 studies 59 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 . Secondary outcomes of self-reported/subjective anxiety and depression comprised of 20 studies 64 , 65 , 66 , 67 , 68 , 69 , 70 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 and 18 studies 64 , 65 , 66 , 67 , 69 , 70 , 71 , 72 , 74 , 78 , 79 , 80 , 81 , 82 , 85 , 86 , 87 , 88 , respectively. Please see Online Appendix B for more information on the secondary outcomes.

Summary of findings for stress

In terms of data extraction, all studies provided raw M ± SD scores apart from two 55 , 56 where estimated marginal M ± SDs were given (raw data was requested from corresponding authors but could not be obtained). One study 65 required SDs from Ms and 95% confidence intervals (CIs) provided, both of which were calculated in accordance with Cochrane Collaboration guidelines 48 . Furthermore, another study 70 required two groups’ M ± SD scores (there was one control group and two intervention groups) to be combined and two further studies 64 , 71 involved crossover designs (hence data were extracted at the midpoints of each study before controls started the breathwork intervention). Analyses of follow-up scores were not possible for self-reported/subjective stress as there were insufficient studies for results to be reliably interpreted 58 .

The 12 studies included in the meta-analysis for the primary outcome of stress were completed from 2012 to 2021 (seven, or 60%, were conducted from 2020 onwards). Half of these studies were conducted in the US 59 , 64 , 65 , 66 , 68 , 74 , two in India 71 , 72 , one globally 73 , and one each in: Israel 70 , Turkey 67 , and Canada 69 . The average age was 41.7 (± 8.47) and 75% identified as female, since the largest study 68 was for women only. Attrition rates (after the breathwork intervention began) ranged from 3 to 40%. Participant sample sizes ranged from 10 to 150, with the total number of participants analysed being 785. The number of participants randomised to a breathwork intervention or control condition was 417 and 368, respectively. The minimum total estimated durations of an intervention/home practice ranged from 80 to 5625 min.

Half of the studies comprised physical health, five nonclinical, and one mental health samples. Ten and two studies comprised interventions with a primary focus on slow-paced breathing and fast-paced breathing, respectively. Seven were individual-based interventions, four taught to groups, and one a combination of both modes. Half were remote/self-help interventions, five in-person, and one combination. Seven and five studies had inactive and active control groups, respectively. Eight studies used the perceived stress scale (PSS) 89 , three used the stress subscale from the depression anxiety stress scale (DASS) 90 , and one used the perceived stress questionnaire (PSQ) 91 .

Risk of bias for stress

Risk of bias scoring for the 12 studies on the primary outcome is reported using RoB 2 in Fig.  2 . Three studies’ overall assessment were algorithmically scored as being at high risk of bias, with domain two (deviations from the intended interventions) contributing to most bias. The remaining nine studies’ overall risk of bias were algorithmically scored as having some concerns. Only one study did not disclose how randomisation was conducted. Most of the domains, from randomisation to selection of the reported result, were scored as having some concerns or low risk of bias. We did not find reported adverse events or lasting bad effects directly attributed to breathwork interventions; four studies (six in total including secondary outcome studies) actively reported on this. Nonetheless, regarding safety and tolerability, a small subgroup of participants in Ravindran et al.’s study 71 focusing on fast-paced breathwork in unipolar and bipolar depression reported side effects such as hot flushes, shortness of breath and/or sweating. However, these participants opted to continue the intervention and no participants dropped out of the breathwork group due to adverse effects.

Risk of bias scoring using Cochrane Collaboration’s RoB 2 tool. Green and red colours correspond to low and high risk of bias, respectively. Yellow represents some concerns. D1 Randomisation process, D2 Deviations from the intended interventions, D3 Missing outcome data, D4 Measurement of the outcome, D5 Selection of the reported result.

As shown in Fig.  3 , the random-effects meta-analysis (k  = 12) displayed a small-medium but significant post-intervention between-group ES, g  = − 0.35 [95% CI − 0.55, − 0.14], z  = 3.32, p  = 0.0009, denoting breathwork was associated with lower levels of self-reported/subjective stress at post-intervention than controls. There were insufficient studies including follow-up measures for a meta-analysis. Heterogeneity was moderate but non-significant, χ 2 11  = 19, p  = 0.06, I 2  = 42%. Via removing one individual study at a time, the ES of breathwork on stress ranged from − 0.27 to − 0.39 and remained significant in all cases. Initial visual inspection of the funnel plot in Online Appendix  C suggested some skew due to studies with small samples; however, the Egger’s test was non-significant, z  = 0.03, p  = 0.947, indicating a low chance of publication bias. Fail-safe N  analysis denoted that a further 69 studies yielding zero effect would need to be added to make the overall ES non-significant for stress. On removal of the one potential outlier 67 the ES remained significant but became smaller: − 0.27. On removal of the two studies using estimated marginal M ± SDs, the ES remained significant and became larger: − 0.40.

Forest plot comparing breathwork interventions to non-breathwork control groups on primary outcome of self-reported/subjective stress at post-intervention. Squares and their size represent individual studies and their weight, respectively. Lines through squares are 95% CIs and diamond is the overall effect size with 95% CIs. More negative values denote larger effect of breathwork on self-reported/subjective stress in comparison to control condition. Effect sizes calculated using Hedges’ g . Figure produced using RevMan v5.4.

Subgroup analyses for stress

As displayed by Table 1 , we conducted five sub-analyses for the primary outcome self-reported/subjective stress. There were no significant differential effects between subgroups.

There was a significant effect of breathwork on stress in nonclinical samples, but not in mental (only one study) or physical health populations. Moreover, significant effects were yielded when breathwork was primarily focused on slow-paced breathing (but not for fast-paced breathing), taught to individuals alone, and when taught to groups (but not in combination, which comprised only one study). There were also significant effects of breathwork on stress when the intervention was taught remotely, in-person, and using a combination of these two delivery methods. Significant effects existed for both active and inactive control groups. There were significant effects for studies which used PSS and DASS measures (but not the PSQ, used by only one study).

Heterogeneity was high for studies with physical health samples, slow-paced breathwork, when breathwork was taught to groups and in-person, plus those studies with inactive controls, and when stress was measured by using the DASS, suggesting potential moderating factors that were not accounted for by the subgroup analyses. There was no significant correlation between estimated total duration of breathwork intervention/home practice and ES ( n  = 12) τ B  = − 0.05, p  = 0.418, number of intervention/home practice sessions and ES for stress ( n  = 12) τ B  = − 0.28, p  = 0.107, nor for intervention/home practice session frequency and ES ( n  = 12) τ B  = − 0.17, p  = 0.224.

Breathwork and secondary outcomes

In terms of data extraction, one study 79 had a measure with positively scored anxiety and depression subscales; accordingly, we subtracted the subscale score from the maximum score to reverse the polarity of the measure without changing the magnitude of difference. Another study 88 required two groups’ M ± SD scores to be combined. Analysis of follow-up scores were not possible for secondary outcomes as there were insufficient studies 58 ( n  < 5). Forest plots for the secondary outcomes are reported in Online Appendix  D . Random-effects analysis for anxiety ( k  = 20) showed a significant small-medium between-group ES in favour of breathwork, g  = − 0.32 [95% CI − 0.48, − 0.16], z  = 3.90, p  < 0.0001, with moderate and significant heterogeneity, χ 2 19  = 38.62, p  = 0.005, I 2  = 51%. Sensitivity analysis showed ESs ranging from − 0.29 to − 0.34, significant in all cases. No individual study was responsible for the significant heterogeneity. Random-effects analysis for depression ( k  = 18) displayed a significant small-medium ES in favour of breathwork, g  = − 0.40 [95% CI − 0.58, − 0.22], z  = 4.27, p  < 0.0001, and heterogeneity was moderate and significant, χ 2 17  = 40.5, p  = 0.001, I 2  = 58%. Sensitivity analysis showed ESs ranging from − 0.35 to − 0.44, significant in all cases. On removal of two potential outliers 85 , 88 , the ES remained the same. No single study was responsible for the significant heterogeneity.

We conducted the first comprehensive systematic review and meta-analysis of RCTs on the effect of breathwork on self-reported/subjective stress, analysing 12 studies which comprised a total of 785 participants. Breathwork yielded a significant post-intervention between-group effect of breathwork on stress compared to non-breathwork controls, denoting breathwork was associated with lower levels of stress than controls.

Statistical heterogeneity was moderate but not significant, meaning variance in ESs was likely explained by breathwork rather than other variables, although this non-significance could also be a consequence of the low number of studies included. This small-medium ES should be interpreted in the light of moderate risk of bias overall for the 12 studies. More than half of the studies included in our meta-analysis for stress were completed from 2020 onwards, suggesting a recent emergence of research into breathwork, which may have been accelerated by the covid-19 pandemic. Research on breathwork could be likened to that of meditation, which received an unprecedented surge in scientific exploration two decades ago 92 . We may be at a similar cusp with breathwork and anticipate considerable growth in the field. Given the close ties of breathwork to psychedelic research 93 , which is growing rapidly, this could accelerate growth further.

Regarding subgroup analyses for self-reported/subjective stress, heterogeneity was significant for studies with physical health samples, slow-paced breathwork interventions, inactive control groups, along with studies when breathwork was group-based and in-person. At present, there are too few studies within the sub-analyses to address this issue of statistical heterogeneity. Overall, point estimates were similar and sample sizes were small, hence where results were non-significant, it is unclear whether there was genuinely no effect, or lack of statistical power. Furthermore, no significant differential effects across subgroups were observed, but this could also be the result of the scarce number of studies.

While nonclinical samples showed a significant effect on self-reported/subjective stress outcomes and physical and mental health samples did not, between-subgroup differences were non-significant and the point estimates for these subgroups were similar (ranging from ES = 0.26–0.38). These findings could mean that breathwork is not effective for physical/mental health populations, however, it is also possible that this analysis was underpowered to detect effects given the relatively small number of studies contributing to the subgroups, as we have already mentioned. There were only two studies primarily focused on fast-paced breathwork and stress, insufficient to make a meaningful comparison with the ten studies primarily focused on slow-paced breathwork. Interestingly, delivery modes and styles did not seem to influence the results, which may suggest breathwork can be learned through several different formats. Half of the studies’ interventions were delivered remotely without instructors (self-help), hence breathwork could potentially be widely disseminated and thus accessible and probably scalable. The results were significant for both active and inactive controls, although it would be expected that breathwork would have less effect compared to active controls. This could be due to poor quality of the active controls. Lastly, results were significant for two of three stress outcome measures, most likely due to them being psychometrically well-validated—only one study used the third measure (PSQ).

Concerning dose–response, although associations were in the expected direction, there were no significant correlations between the minimum estimated durations of breathwork intervention/home practice and ES, for all outcomes. This apparent absence of dose–response effects was surprising as increased practice time might be expected to be associated with greater benefit, however compliance to intervention home practice was not reported for many studies and so true dose–response analysis was not possible. Moreover, intention-to-treat analysis data were used for the most conservative estimates of effect. Dhruva et al.’s study 64 included in our meta-analysis specifically investigated dose–response effects, finding a positive relationship between total amount of breathwork intervention/home practice and improvement in quality of life and chemotherapy-associated symptomology—there was a significant decrease in anxiety for each hour increase in breathwork. Alternatively, this could be indicative of breathwork being possibly able to help quickly, as suggested in very recent literature whereby just one session of slow, deep breathing had beneficial effects on anxiety and vagal tone in adults 94 , with vagal tone being measured, albeit indirectly, through HRV 6 . This may be likened to ‘micro dosing’ breathwork, similar to single session mindfulness meditation practices 95 .

The meta-analysis results are largely consistent with and extend upon previous work. For instance, our findings are somewhat in line with Malviya et al.’s recent review which provides some support for breathwork’s effectiveness in alleviating stress 43 . However, this review only included two studies for stress, one of which comprised of both groups incorporating breathing practices (and was thus excluded from our meta-analysis). Hopper et al.’s systematic review on diaphragmatic breathing found just one RCT for stress, however this used physiological measures 42 . Nonetheless, this study showed that the stress hormone cortisol was lower in people undergoing slow-paced breathwork compared to controls 96 . In a different study 38 , participants administered with bacterial endotoxin ( E. coli ) who performed fast-paced breathwork had higher spikes of cortisol compared to non-breathwork controls, during the intervention, but a quicker recovery and stabilisation of cortisol levels after cessation of breathwork. This could be another mechanism of action warranting further investigation.

Breathwork, anxiety and depression

Furthermore, meta-analyses comprising 20 and18 studies run for secondary outcome measures of self-reported/subjective anxiety and depressive symptoms, showed that breathwork interventions also yielded significant small-medium ESs in comparison to controls, favouring breathwork (see Online Appendix  D for results). However, heterogeneity was significant for both outcomes, meaning the variance in ESs may be due to other variables apart from breathwork. Thus, these ESs should be interpreted with caution and need further research. As per Malviya et al.’s review 43 , greater support was offered for breathwork in alleviating anxiety and depressive symptoms (eight studies for both outcomes). The review deemed findings pertaining to the efficacy of breathwork in decreasing anxiety and depression as promising. This was also consistent with Zaccaro et al.’s review findings on slow breathing (15 studies—no RCTs), that had lower self-reported anxiety and depression, possibly linked to increased HRV measured during interventions 4 . Ubolnuar et al.’s review of breathing exercises for COPD found no significant effect on anxiety and depression from a subgroup meta-analysis of two RCTs, however the interventions used for both were singing classes 39 . Nonetheless, a recent meta-analysis by Leyro et al. of 40 RCTs on interventions for anxiety, which comprised a respiratory component (ranging from diaphragmatic breathing to capnometry assisted respiratory training), showed such treatments were associated with significantly lower symptoms of anxiety compared to control groups 41 . Though non-respiratory controls were used, respiratory components did not have to form a significant part of the intervention, thus it is less possible to tease out the effects of such techniques. While some interventions used physically altering equipment such as training of musculature involved in respiration, this might provide further potential for breathwork-related work in clinical conditions.

Comparison to stress-reduction interventions

Through estimating statistically significant differences and 95% CIs among studies 97 , in comparison to interventions for stress, our findings suggest that breathwork might be associated with similar—and non-significantly different—effects. For instance, Heber et al.’s meta-analysis on computer- and online-based stress interventions, including CBT and third-wave CBT (e.g., inclusion of meditation, mindfulness, or acceptance of emotions) compared to controls in adults, found moderate effects on stress, d  = 0.43 [95% CI 0.31, 0.54], anxiety, d  = 0.32 [95% CI 0.17, 0.47], and depression, d  = 0.34 [95% CI 0.21, 0.48] 98 . Each of these effects overlap more than 25% with the width of either interval in our results for breathwork, denoting no indication of a clinically relevant difference between the interventions. Similar meta-analytic findings concerning effects on stress, anxiety and depression have been found for related and more analogous techniques such as mindfulness-based cognitive therapy and stress reduction (MBCT/MBSR) 99 along with self-help (MBSH) 100 . While Pizzoli et al.’s recent post-intervention HRVB meta-analysis (14 published RCTs) 13 found a significant effect on depression, another meta-analysis did not find a significant effect on stress, with the smallest ES being yielded for self-reported stress out of myriad outcomes 14 . Lastly, a meta-analysis of eight meta-analytic outcomes of RCTs on physical activity 99 showed similar significant effects on depression and anxiety. While we are not proposing breathwork as a substitute for other treatments, it could complement other therapeutic interventions, potentially leading to additive effects of such health behaviours.

People with stress and anxiety disorders tend to chronically breathe faster and more erratically, yet with increased meditation practice, respiration rate can become gradually slower, potentially translating into better health and mood, along with less autonomic activity 92 . Positive impacts on HRV may partially explain some of the mechanisms behind mindfulness meditation 101 , 102 . However, the above approaches like MBCT/MBSR and HRVB may be less accessible. MBCT/MBSR teacher training takes at least one year while HRVB is routinely taught by a qualified healthcare professional; this is usually a prerequisite and most certified biofeedback therapists are habitually licensed medical providers, including general practitioners, psychiatrists, dentists, nurses, and psychologists 103 . MBCT/MBSR and HRVB therapist training includes theoretical/practical curricula, while breathwork teacher training can be more quickly and easily taught (i.e., over days and weeks) online and remotely to both healthcare professionals and the general population, thus potentially proving cost-effective.

Two of our studies used the only Food and Drug Administration-approved portable electronic biofeedback device, which encourages deep, slow breathing 103 . However, HRV can be improved in the same way (tenfold) by simply breathing at a rate around 5–6 breaths/min 104 and some Zen Buddhist monks have been found to naturally respire around this rate during deep meditation 105 . It may be possible that breathing rate forms a key component of meditation’s known positive effects. Indeed, it has been shown that HRV can be modulated during the practice of meditation 106 . However, a recent meta-analysis on this exact matter found insufficient evidence suggesting mindfulness/meditation led to improvements in vagally mediated HRV, and more well-designed RCTs without high risk of bias are needed to clarify any such contemplative practices’ impact on this physiological metric 107 , along with potential mechanisms related to cortisol.

Traditional mindfulness-based programmes frequently involve meditation requiring observation of the breath, using it as an object of awareness, not voluntary regulation of respiration like in breathwork. Such breath-focus may be a key active ingredient and potential mechanism of action of the former contemplative practices, since highly experienced meditators have been found to breathe at over 1.5 times slower than nonmeditators, during meditation and at rest 108 . This translates into approximately 2000 less daily breaths for the former group of adept meditation practitioners (i.e., around 700,000 less breaths in a year), placing less demand on the ANS 92 . Meditation could also be complementary; voluntary upregulation of HRV through biofeedback may be improved by mental contemplative training 109 . While there is a possibility that it could simply be the cognitive-attentional components of both meditation and breathing practices that explain their effects, observation of the breath (i.e., most practices within mindfulness curricula) versus control of the breath (i.e., breathwork) warrants nuanced investigation.

Strengths, limitations and future directions

Our systematic review searched published, unpublished and grey literature across numerous electronic databases and the meta-analysis comprised several very recent RCTs with well-validated measures of self-reported/subjective stress. However, like most systematic reviews in this field, given the small sample size (likely due to the recent phenomena of breathwork in the West) and moderate risk of bias across the studies included in our meta-analysis, our results should be interpreted cautiously. Future studies exploring breathwork’s effectiveness should aim for research designs with low risk of bias. While this review attempted to bridge the gap and unify both old and new research, future low risk-of-bias studies are now needed in order to draw definitive conclusions of breathwork’s impact on mental health. There were also not enough studies for valuable subgroup comparisons, and therefore we did not identify any potential sources of heterogeneity. Furthermore, secondary outcomes were not scrutinised with the same level of detail as the primary outcome, as they were only used to provide complementary context and a bigger picture around stress and mental health in general.

Our meta-analysis is the first review of breathwork’s impact on self-reported/subjective stress and its therapeutic potential, and combining this quantitative synthesis of psychological effects of breathwork with other syntheses, i.e., of physiological effects 4 , could help build a stronger psychophysiological model of breathwork’s efficacy along with more robust mechanisms of action. Studies could use stress subscales in DASS as standard in addition to the anxiety/depression scales, as this could be important for nonclinical and subclinical populations experiencing stress and allow for direct comparison of effects across clinical/nonclinical populations. Additionally, psychophysiological RCTs combining both subjective and objective measures in line with proposed mechanisms of action (i.e., self-reported stress and ECG HRV/respiration rate measurements) should be conducted, along with further imaging (MRI, EEG, NIRS, etc.) studies on various breathwork techniques (only one fMRI study was available in Zaccaro et al.’s review 4 ). This could help better determine modalities and underlying principles of different breathwork techniques. Though validated scales were used for stress in the meta-analysis, our review lacks objective outcomes, which increases risk of bias further.

Comparison groups promoting observation versus control of the breath could yield interesting findings when exploring any differences between the effects of meditation and breathwork. However, robust scientific methods that align well with current methodological demands on meditation and contemplative psychological science 110 should be implemented. There was also limited scope to report on follow-up effects, hence more studies could include true follow-up timepoints and longitudinal designs, now more common in meditation and contemplative science research. On top of this, there could be cross-cultural differences in response to breathwork (i.e., between Eastern and Western modalities) which could be explored by future research, along with searching non-English language literature. There could also be differences between age categories (including children); this meta-analysis focused solely on adults across a broad age-range. Lastly, more studies should report on adverse events and lasting bad effects, with further research needed to gauge the safety profile of fast-paced breathwork in particular, so it not administered blindly to potentially vulnerable populations.

Clinical implications

For stress, though not many studies monitored home practice/self-practice, engagement with interventions appeared good, none reporting adverse effects directly attributed to breathwork. This suggests breathwork has a high safety profile and slow-paced breathing techniques can be recommended to subclinical populations or those experiencing high stress. However, regarding clinical populations, the findings from our meta-analysis show non-significant effects for mental and physical health populations, hence it could be premature to recommend breathwork in these contexts. If breathwork can indeed provide therapeutic benefit to specific populations, conducting research with strong, low risk-of-bias design is essential to understanding if breathwork is genuinely effective or not. Ethicality should always take centre stage, with first doing no harm being the priority. Nonetheless, in nonclinical settings (excluding those predisposed to mental and physical health conditions), the low cost and risk profiles make breathwork (primarily focused on slow-paced breathing), scalable, with evidence from this meta-analysis that some techniques can potentially be self-learned, not requiring an instructor in real-time. Providing future robust research shows positive effects of breathwork, only then can an evidence-based canon be borne out of breathwork, using standardised and manualised materials for both training and practicing various secular, accessible techniques. However, there is a possibility rigorous research demonstrates that breathwork is not effective. Moreover, precaution must be exercised at all times; clinicians should consider for the individual whether breathwork may exacerbate the symptoms of certain mental and/or physical health conditions (cf. Muskin et al. 111 ).

Conclusions

More accessible therapeutic approaches are needed to reduce, or build resilience to, stress worldwide. While breathwork has become increasingly popular owing to its possible therapeutic potential, there also remains potential for a miscalibration, or mismatch, between hype and evidence. This meta-analysis found significant small-medium effects of breathwork on self-reported/subjective stress, anxiety and depression compared to non-breathwork control conditions. Breathwork could be part of the solution to meeting the need for more accessible approaches, but more research studies with low risk-of-bias designs are now needed to ensure such recommendations are grounded in research evidence. Robust research will enable a better understanding of breathwork’s therapeutic potential, if any. The scientific research community can build on the preliminary evidence provided here and thus, potentially pave the way for effective integration of breathwork into public health.

Data availability

The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.

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Acknowledgements

G.W.F. has a doctoral scholarship from—and is a Fellow of—The Ryoichi Sasakawa Young Leaders Fellowship Fund, Sylff Association, Tokyo. J.M.M. has a “Miguel Servet” research contract from the ISCIII (CP21/00080). J.M.M. is grateful to the CIBER of Epidemiology and Public Health (CIBERESP CB22/02/00052; ISCIII) for its support. Authors thank Dr. Patricia L. Gerbarg, M.D., and Dr. Frances Meeten for reading the manuscript and providing feedback prior to submission for publication. Thank you Dr. Daron A. Fincham for proofreading a final copy of the manuscript.

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G.W.F. was responsible for securing funding for the programme of work to which this contributes, conceived the initial idea, and was responsible for leading the meta-analysis. G.W.F. and J.M.M. conducted the literature search. C.S. and K.C. supervised the entire process. G.W.F. conducted the analysis with support from C.S., K.C., and J.M.M. All authors discussed the data and clinical implications of the study. G.W.F. and J.M.M. conducted the risk-of-bias evaluations. G.W.F. drafted the manuscript, with input from C.S., K.C., and J.M.M. All authors read and revised drafts and approved the final manuscript. Each section of the manuscript was discussed among all authors.

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Fincham, G.W., Strauss, C., Montero-Marin, J. et al. Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials. Sci Rep 13 , 432 (2023). https://doi.org/10.1038/s41598-022-27247-y

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Research: Why Breathing Is So Effective at Reducing Stress

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Studies found it outperformed other techniques over both the short and long term.

Anxiety in the workplace is a serious problem. What can you do to stay calm, rational, and productive when dealing with a stressful situation? In several recently published studies, the authors explored the effectiveness of different techniques and found that one method — SKY Breath Meditation — offered the best results for both immediate and long-term stress reduction. This comprehensive series of breathing and meditation exercises engages the parasympathetic nervous system, which is responsible for the body’s “rest and digest” activities, helping you to calm down and think rationally in the face of stress. These simple techniques can help you sustain greater emotional wellbeing and lower your stress levels at work and beyond.

When U.S. Marine Corp Officer Jake D.’s vehicle drove over an explosive device in Afghanistan, he looked down to see his legs almost completely severed below the knee. At that moment, he remembered a breathing exercise he had learned in a book for young officers. Thanks to that exercise, he was able to stay calm enough to check on his men, give orders to call for help, tourniquet his own legs, and remember to prop them up before falling unconscious. Later, he was told that had he not done so, he would have bled to death.

• Emma Seppälä , PhD, is a faculty member at the Yale School of Management, faculty director of the Yale School of Management’s Women’s Leadership Program and bestselling author of SOVEREIGN (2024) and The Happiness Track (2017). She is also science director of Stanford University’s Center for Compassion and Altruism Research and Education . Follow her work at emmaseppala.com , http://www.iamsov.com or on Instagram . emmaseppala
• Christina Bradley is a doctoral student in the Management & Organizations department at the University of Michigan’s Ross School of Business. Her research focuses on how to talk about emotions at work.
• Michael R. Goldstein , Ph.D., is a Postdoctoral Research Fellow at Beth Israel Deaconess Medical Center and Harvard Medical School. He is a Licensed Clinical Psychologist and his research examines the physiological mechanisms of mind-body interventions for insomnia.

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In contrast to blood and urine samples, breath is invisible and ubiquitous in the environment. Different precautions are now necessary beyond the usual 'Universal Precautions'. In the era of COVID-19, breath (especially the aerosol fraction) can no longer be considered as harmless in the clinic or laboratory. As Journal of Breath Research is a primary resource for breath-related research, we (the editors) are presently developing safety guidance applicable to all breath research , not just for those projects that involve known COVID-19 infected subjects. We are starting this process by implementing requirements on reporting safety precautions in research papers and notes. This editorial announces that authors of all new submissions to JBR henceforth must state clearly the procedures undertaken for assuring laboratory and clinical safety, much like the existing requirements for disclosing Ethics Committee or Institutional Review Board protocols for studies on human subjects. In the following, we additionally make some recommendations based on best practices drawn from our experience and input from the JBR Editorial Board.

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January 15, 2019

11 min read

Proper Breathing Brings Better Health

Stress reduction, insomnia prevention, emotion control, improved attention—certain breathing techniques can make life better. But where do you start?

By Christophe André

Breathing is like solar energy for powering relaxation: it’s a way to regulate emotions that is free, always accessible, inexhaustible and easy to use.

Ruslan Ivanov Getty Images

As newborns, we enter the world by inhaling. In leaving, we exhale. (In fact, in many languages the word “exhale” is synonymous with “dying.”) Breathing is so central to life that it is no wonder humankind long ago noted its value not only to survival but to the functioning of the body and mind and began controlling it to improve well-being.

As early as the first millennium B.C., both the Tao religion of China and Hinduism placed importance on a “vital principle” that flows through the body, a kind of energy or internal breath, and viewed respiration as one of its manifestations. The Chinese call this energy qi, and Hindus call it prana (one of the key concepts of yoga).

A little later, in the West, the Greek term pneuma and the Hebrew term rûah referred both to the breath and to the divine presence. In Latin languages, spiritus is at the root of both “spirit” and “respiration.”

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Recommendations for how to modulate breathing and influence health and mind appeared centuries ago as well. Pranayama (“breath retention”) yoga was the first doctrine to build a theory around respiratory control, holding that controlled breathing was a way to increase longevity.

In more modern times, German psychiatrist Johannes Heinrich Schultz developed “autogenic training” in the 1920s as a method of relaxation. The approach is based partly on slow and deep breathing and is probably still the best-known breathing technique for relaxation in the West today. The contemporary forms of mindfulness meditation also emphasize breathing-based exercises.

In fact, every relaxation, calming or meditation technique relies on breathing, which may be the lowest common denominator in all the approaches to calming the body and mind. Research into basic physiology and into the effects of applying breath-control methods lends credence to the value of monitoring and regulating our inhalations and exhalations.

Yoga and meditation have inspired many of the breathing exercises used today. The benefits of controlled respiration were first theoretically posited centuries ago by the practitioners of pranayama yoga. Credit: Getty Images

Mind under the Influence

Even a rudimentary understanding of physiology helps to explain why controlled breathing can induce relaxation. Everyone knows that emotions affect the body. When you are happy, for instance, the corners of your mouth turn up automatically, and the edges of your eyes crinkle in a characteristic expression. Similarly, when you are feeling calm and safe, at rest, or engaged in a pleasant social exchange, your breathing slows and deepens. You are under the influence of the parasympathetic nervous system, which produces a relaxing effect. Conversely, when you are feeling frightened, in pain, or tense and uncomfortable, your breathing speeds up and becomes shallower. The sympathetic nervous system, which is responsible for the body’s various reactions to stress, is now activated. Less well known is that the effects also occur in the opposite direction: the state of the body affects emotions. Studies show that when your face smiles, your brain reacts in kind—you experience more pleasant emotions. Breathing, in particular, has a special power over the mind.

This power is evident in patients who have breathing difficulties. When these difficulties are sporadic and acute, they can trigger panic attacks; when they are chronic, they often induce a more muted anxiety. It is estimated that more than 60 percent of people with chronic obstructive pulmonary disease (COPD) have anxiety or depressive disorders. These disorders probably stem in part from concerns about the consequences of the disease (what could be more distressing than struggling to breathe?), but purely mechanical factors may contribute as well: the difficulty these patients experience often leads to faster breathing, which does not necessarily improve the quality of their oxygen supply but can aggravate their physical discomfort and anxiety.

Rapid breathing can contribute to and exacerbates panic attacks through a vicious circle: fear triggers faster breathing, which increases fear. In 2005 Georg Alpers, now at the University of Mannheim in Germany, and his colleagues observed significant and unconscious hyperventilation when people who had a driving phobia took their vehicles on the highway (where they might not be able to pull over if they become agitated).

Whether anxiety derives from breathing problems or other causes, it can be eased by a number of breathing techniques derived from traditional Eastern approaches (see “Six Techniques for Relieving Stress”). For example, “follow your breath,” an exercise that focuses attention on breathing, is one of the first steps in mindfulness meditation, whereas alternate nostril breathing comes from yoga. Combining reassuring thoughts with breathing is an approach incorporated into sophrology, a technique that emphasizes harmony of body and mind and that borrows exercises from many approaches, including yoga and mindfulness.

Overall, research shows that these techniques reduce anxiety, although the anxiety does not disappear completely. Breathing better is a tool, not a panacea. Some methods have been validated by clinical studies; others have not. But all of those I describe in this article apply principles that have been proved effective. They aim to slow, deepen or facilitate breathing, and they use breathing as a focal point or a metronome to distract attention from negative thoughts.

Spotlight on Cardiac Coherence

A close look at one popular technique—cardiac coherence—offers more detail about the ways that breathing exercises promote relaxation. With the help of biofeedback, the approach attempts to coordinate breathing with heart rate, slowing and steadying breathing to slow and stabilize the heartbeat.

The method was developed based on the understanding that slow, deep breathing increases the activity of the vagus nerve, a part of parasympathetic nervous system; the vagus nerve controls and also measures the activity of many internal organs. When the vagus nerve is stimulated, calmness pervades the body: the heart rate slows and becomes regular; blood pressure decreases; muscles relax. When the vagus nerve informs the brain of these changes, it, too, relaxes, increasing feelings of peacefulness. Thus, the technique works through both neurobiological and psychological mechanisms.

Cardiac coherence’s stabilization of the heartbeat can dampen anxiety powerfully. Conversely, patients with overactive heartbeats are sometimes misdiagnosed as victims of panic attacks because their racing heartbeat affects their mind.

A typical cardiac coherence exercise involves inhaling for five seconds, then exhaling for the same amount of time (for a 10-second respiratory cycle). Biofeedback devices make it possible to observe on a screen how this deep, regular breathing slows and stabilizes the beats. (The space between two heartbeats on the display is never exactly the same, but it becomes increasingly more consistent with this technique.) Several studies have confirmed the anxiety-diminishing effect of these devices, although the equipment probably has more influence on the motivation to do the exercises (“It makes it seem serious, real”) than on the physiological mechanisms themselves. Simply applying slow breathing with the same conviction and rigor could well give the same result.

Some versions of cardiac coherence recommend spending more time on exhaling than on inhaling (for example, six and four seconds). Indeed, your heart rate increases slightly when you inhale and decreases when you exhale: drawing out the second phase probably exerts a quieting effect on the heart and, by extension, on the brain. This possibility remains to be confirmed by clinical studies, however.

Other work suggests that the emotional impact of the breathing done in cardiac coherence and various other kinds of exercises stems not only from effects on the periphery—on the parasympathetic nervous system—but also from effects on the central nervous system. Breathing may well act directly on the brain itself.

In 2017, for instance, Mark Krasnow of Stanford University and his colleagues showed in mice that a group of neurons that regulates respiratory rhythms (the pre-Bötzinger complex in the brain stem) controls some of the activity of the locus coeruleus, a region involved in attention, wakefulness and anxiety. Breathing techniques may influence this seat of emotions by modulating the activity of the pre-Bötzinger complex.

Beyond any direct effects produced by slowed breathing, the attention given to inhaling and exhaling may play a role in the brain’s response. In 2016 Anselm Doll and his colleagues, all then at the Technical University of Munich, showed that this attentional focus eases stress and negative emotions, in particular by activating the dorsomedial prefrontal cortex, a regulatory area of the brain, and by reducing activity in the amygdala, which is involved in these emotions.

In addition, paying attention to breathing causes most people to slow it down and to deepen it, which as I have mentioned, is soothing. Cognitive resources are limited, and so when individuals concentrate on breathing, they are not thinking about their worries. Those who practice mindfulness learn to notice when their attention drifts away from breathing and goes back to their concerns, and they train themselves to return periodically to their breathing. This refocusing has a relaxing effect on anyone and helps to combat ruminative thinking in people who have anxiety or depression, especially those who are particularly prone to negative thoughts that run in a loop.

When to Use Breathing Techniques

What is the best time to apply slow-breathing techniques? One is during occasional episodes of stress—for example, before taking an exam, competing in a sporting event or even attending a routine meeting at work. In 2017 Ashwin Kamath of Manipal University in India and his colleagues studied stage fright before a public speaking engagement. The participants, all medical students, spent 15 minutes doing alternate nostril breathing—that is, slowly inhaling through one nostril and exhaling through the other by applying finger pressure to the side of the nose not being used. Compared with members of the control group, participants experienced somewhat less stress when speaking publicly.

These exercises may also help when insomnia strikes. In 2012 Suzanne M. Bertisch of Harvard Medical School and her colleagues reported, based on survey data, that more than 20 percent of American insomniacs do these breathing exercises to sleep better. They may be on to something. In 2015 Cheryl Yang and her team at National Yang-Ming University in Taiwan showed that 20 minutes of slow breathing exercises (six respiration cycles per minute) before going to bed significantly improves sleep. Insomniac participants went to sleep faster, woke up less frequently in the night and went back to sleep faster when they did wake up. On average, it took them only 10 minutes to fall asleep, almost three times faster than normal. The investigators attributed the results both to the calming mediated by the parasympathetic system and to the relaxing effect of focused breathing.

But respiratory techniques do not work only for acute stresses or sleep problems; they can also relieve chronic anxiety. They are particularly effective in people with psychiatric disorders such as phobias, depression and post-traumatic stress disorder. In 2015 Stefania Doria and her colleagues at Fatebenefratelli e Oftalmico Hospital in Milan, Italy, offered 10 training sessions of two hours each, spread out over two weeks, to 69 patients with anxiety or depressive disorders. The training included a varied set of breathing techniques (such as abdominal breathing, acceleration and deceleration of rhythm, and alternate nostril breathing.), combined with some yoga stretches. The researchers observed a significant decrease in symptoms at the end of the protocol. Even better, improvement was maintained two and six months later, with follow-up sessions just once a week and some home practice during this period.

Breathing exercises also help to counter the accumulation of minor physical tension associated with stress. Therapists recommend doing them regularly during the day, during breaks or at moments of transition between two activities: you simply stop to adjust your posture and allow yourself a few minutes of quiet breathing. Therapists often suggest the “365 method”: at least three times a day, breathe at a rhythm of six cycles per minute (five seconds inhaling, five seconds exhaling) for five minutes. And do it every day, 365 days a year. Some studies even suggest that, in addition to providing immediate relief, regular breathing exercises can make people less vulnerable to stress, by permanently modifying brain circuits. In a practice that may seem counterintuitive, however, counselors may encourage some anxious patients to breathe rapidly instead of slowly, as part of an effort to train them to cope with their anxieties (see box “Inhale for Panic!”).

But why confine breathing techniques to negative emotions? It is also worth applying them during pleasurable moments, to take the time to appreciate and remember them. In short, one can pause and breathe for enjoyment as well as to calm down.

Open Questions

Tradition and experience encourage the use of respiratory-control techniques, and scientific studies increasingly suggest that it is a good idea. Nevertheless, further research is still needed, particularly given that some studies lack control groups. One exception stands out: focusing on breathing often is not a good idea for people having a panic attack that stems from anxiety over their physical state (also known as interoceptive anxiety). In this case, focusing on physiology, such as muscle tension or breathing, may actually amplify panic (“Now that I’m paying attention to it, my breathing doesn’t seem regular. Am I choking? What will happen if I suddenly stop breathing?”) For these people, breathing techniques should be tested and practiced under the supervision of a therapist.

Otherwise, considering how often everyone experiences emotional discomfort in their everyday life and its negative consequences on health, we would all do well to regularly pay attention to the way we breathe. Start with brief periods of conscious, quiet breathing several times a day. Breathing is like solar energy for powering relaxation: it’s a way to regulate emotions that is free, always accessible, inexhaustible and easy to use.

In fact, I am mystified that controlled breathing is not recommended and practiced more widely. Perhaps it is perceived as too simple, commonplace and obvious to be a remedy. Faced with the complexity of negotiating the ups and downs of human life, many people may assume that simple solutions cannot be effective.

Or maybe we are intimidated by the sacred aspect of breathing, by its connection to life and, especially, to death. In the 1869 novel The Man Who Laughs, Victor Hugo wrote: “Generations are puffs of breath, that pass away. Man respires, aspires, and expires.” Ultimately, we don’t like to think that we are nothing more than “puffs of breath.”

Six Techniques for Relieving Stress

Here are some commonly used breathing techniques. Five to 10 minutes of exercise can relieve sporadic stress and even fend off panic attacks. More regular practice can lower the daily levels of anxiety.

Stand Up Straight

Posture is important for breathing: hold yourself straight, without stiffness, shoulders back, sitting or standing. This body posture facilitates the free play of the respiratory muscles (of the diaphragm and between the ribs). Good posture enables your body to breathe properly on its own.

Follow Your Breath*

Simply observe your respiratory movements: be aware of each inhalation and exhalation. Focus on the sensations you feel as air passes through your nose and throat or on the movements of your chest and belly. When you feel your thoughts drift (which is natural), redirect your attention to your breath.

Abdominal Breathing

Breathe “through your stomach” as much as possible: start by inflating your belly by inhaling, as if to fill it with air, then swell your chest; as you exhale, first “empty” your stomach, then your chest. This type of breathing is easier to observe and test while lying down, with one hand on your stomach.

Rhythmic Breathing

Near the end of each inhalation, pause briefly while mentally counting “1, 2, 3” and holding the air before exhaling. This counting while not breathing can also be done after exhaling or between each inhalation or exhalation. It is often recommended for anxious patients to calm anxiety attacks because it induces a beneficial slowing of the breathing rate.

Alternate Nostrils*

Breathe in and out slowly through one nostril, holding the other one closed using your finger; then reverse and continue by alternating regularly. There are many variations of this exercise—for example, inhaling through one nostril and exhaling through the other. Research suggests that what is most important, aside from slowing the breathing rhythm, is breathing through the nose, which is somewhat more soothing than breathing through your mouth.

Think Reassuring Thoughts While Breathing

With each breath, think soothing thoughts (“I am inhaling calm”). With each exhalation, imagine that you are expelling your fears and worries (“I am exhaling stress”).

*Technique validated by clinical studies.

Inhale for Panic!

Whereas slow breathing soothes, overly rapid breathing can induce feelings of stress and anxiety. This phenomenon is used in behavioral therapy sessions to train anxious patients to confront their emotions directly. By deliberately hyperventilating, patients artificially trigger an unpleasant anxiety, which they get accustomed to feeling and learn to put in perspective. This technique also enables them to see that poor breathing habits amplify their fear.

Christophe André is a psychiatrist at the Sainte-Anne Hospital Center in Paris and a pioneer in the therapeutic use of meditation in France. He has contributed significantly to the practice’s dissemination, especially through his writings, which include the international best seller Mindfulness: 25 Ways to Live in the Moment through Art (Rider, 2014).

Journal of Breath Research

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About Journal of Breath Research

Journal of Breath Research ™ is dedicated to all aspects of scientific research on breath. The traditional focus is on the analysis of volatile organic compounds (VOCs) and aerosols in exhaled breath for the investigation of health status and the diagnosis of disease, exogenous exposures, metabolism and toxicology. The journal also treats the topic of breath odour/malodour (halitosis), as well as welcoming other breath-related topics.

Key areas of interest include (but are not limited to) the following:

• Volatile and non-volatile compounds in exhaled breath gas  (and in other biofluids, e.g., urine, blood, sweat, in correlation with breath)
• Breath biomarkers and the exposome
• Standardization in breath sampling and analysis
• Safety measures in breath collection and handling
• Statistical and chemometric treatment of breath data
• Breath analysis for infectious diseases
• New and emerging technologies in the field
• Methodological aspects of breath research, covering interlaboratory comparisons, validation, and measurement uncertainty
• Physiological modelling of exhaled compounds
• Application in clinical practice
• Exhaled breath condensate and aerosols
• Oral microbiome and malodour production

Why should you publish in Journal of Breath Research?

• High standards: impartial, constructive and rigorous peer review.
• Fast publication: we are committed to providing you with a fast, professional service to ensure rapid first decision, acceptance and publication. Once accepted, your article will be accessible to readers within 24 hours and will include a citable DOI.
• Full compliance with National Institutes of Health (NIH) Public Access Policy—we upload NIH-funded papers to PubMed Central on behalf of authors.
• Open access: open access option—for more details see the IOP Publishing open access policy page .
• Transfer opportunities: as well as accepting direct submissions, the journal also offers you a quick and easy solution to transfer your manuscript from another IOP Publishing journal if it does not fit that journal’s scope or significance criteria. Articles are transferred along with peer review reports to save time and avoid duplication of work for reviewers.
• Society owned: IOP Publishing is a leading society publisher of advanced physics research. Any profits generated by IOP Publishing are invested in the Institute of Physics, helping to support research, education and outreach around the world.

Article types

Journal of Breath Research  welcomes submissions of the following article types:

• Papers:  descriptions of original scientific research, techniques and applications; not normally more than 12 000 words (14 journal pages). All research papers should show strong evidence validating the scientific hypothesis, or the novelty, performance or comparative advantage of the technique or application.
• Notes:  shorter versions of Papers and not normally more than 4000 words (four journal pages).
• Perspectives:  personal view on a particular research topic or discipline.
• Topical reviews:  intended to summarize accepted practice and report on recent progress in selected areas; generally commissioned by the Editorial Board, from experts in various fields.
• Tutorials:  background knowledge of a particular subject area and/or pragmatic explanations of specific procedures used in the field of breath research for an audience unfamiliar with the subject. Tutorials are normally commissioned by the Editorial Board but we also welcome unsolicited submissions to the journal.
• Comments:  comments on, or criticisms of, previously published work; not normally more than 1800 words (two journal pages).

Special requirements

Authors of all articles are required upon submission to disclose any potential conflict of interest (e.g. employment, consulting fees, industrial research contracts, stock ownership, equity interests, patent-licensing arrangements, honoraria, etc.) in their cover letter. If the article is subsequently accepted for publication, this information should be included in an acknowledgments section. Authors should also note that the journal fully endorses the principles embodied in the Declaration of Helsinki in relation to ethical practices in clinical research. All investigations involving humans must be conducted in accordance with these principles and in accordance with local statutory requirements. Articles relying on clinical trials should specify the trial registration number at the end of the abstract. We also encourage the registration of such studies in a public trials registry prior to publication of the results in the journal. All investigations involving animal experimentation must be conducted in conformity with the ‘Guiding Principles for Research Involving Animals and Human Beings’ as adopted by The American Physiological Society.

Safety procedures

On submission, authors are required to describe all the safety procedures adopted in terms of personnel protective measures, safety of breath sampling equipment, safety procedures for the analysis of the collected samples, and finally disposal of collected samples and all potentially contaminated sampling devices.

Contextualizing work for a Journal of Breath Research audience

All articles should emphasize how research will be of interest and of relevance to the breath research community. Authors must emphasize how they have considered breath research as part of their study and refer directly to the impacts the results will have on the field of breath research.

Peer review

The following summary describes the peer review process for Journal of Breath Research , using the ANSI/NISO Standard Terminology for Peer Review :

• Identity transparency: single-anonymous, double-anonymous (author choice)
• Reviewer interacts with: Editor

Our Publishing Support website provides more information on our reviewing process as well as checklists in both English and Chinese language to help authors prepare their manuscripts for submission .

If an article is not accepted for publication, we may offer the author the opportunity to transfer their submission to other suitable journals we publish.

Inclusivity and diversity

IOP Publishing recognises that there are inequalities within the scientific publishing and research ecosystems. We are committed to a progressive approach to inclusivity and diversity, and are working hard to eliminate discrimination to foster an equitable and welcoming publishing environment for all.

IOP Publishing follows  Guidelines on Inclusive Language and Images in Scholarly Communication to ensure that journal articles use bias-free and culturally sensitive communication. We ask authors to please follow these guidelines in their manuscript submissions.

More information about our work on inclusivity is available on our  Open Physics hub .

Research data

Please note that this policy requires authors to include a data availability statement in their article.

For any questions about the policy please contact the journal .

Many research funders now require authors to make all data related to their research available in an online repository. Please refer to the  policy  for further information about research data, data repositories and data citation.

Open access

Alternatively authors who do not select the gold open access option can choose a  green open access  route to publication.

For more information on IOP Publishing’s open access policies please see our  Open access  page. For our author rights policies please see our  Author rights  page.

Publication charges

Publication on a subscription-access basis is free of charge.

Authors have the option to pay the following article publication charge (APC) to publish their article on an  open access  basis under a Creative Commons Attribution  (CC BY) licence .

*excluding VAT where applicable

**eligibility criteria can be found here

APCs only apply to articles accepted for publication; there are no submission charges.

There are no other charges for publishing in Journal of Breath Research .

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Find out if you’re covered by an agreement

If you are covered by an agreement, use our author guide to help you submit your paper.

Countries where we have transformative agreements include: Austria, Canada, Croatia, Finland, Hungary, Ireland, Israel, Germany, Poland, The Netherlands, United Kingdom, Saudi Arabia, Slovenia, Sweden and Switzerland.

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Various discounts, waivers and funding arrangements are available to support our authors. Visit our  Paying for open access page for further details.

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We work with our authors to help make their work as easy to discover as possible.  Journal of Breath Research  is currently included in the following abstracting and discovery services:

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Mind & Body Articles & More

What focusing on the breath does to your brain, different breathing patterns activate our brain networks related to mood, attention, and body awareness, a new study suggests..

Slow down, and pay attention to your breath . It’s not merely commonsense advice. It also reflects what meditation, yoga, and other stress-reducing therapies teach: that focusing on the timing and pace of our breath can have positive effects on our body and mind. A recent study in the Journal of Neurophysiology may support this, revealing that several brain regions linked to emotion, attention, and body awareness are activated when we pay attention to our breath.

Paced breathing involves consciously inhaling and exhaling according to a set rhythm. For example, you might inhale for four counts, exhale for six, and repeat. Prior research shows that paced breathing exercises can both focus attention and regulate the nervous system . To date, however, we have known little about how this affects brain function in humans.

These findings represent a breakthrough because, for years, we’ve considered the brain stem to be responsible for the process of breathing. This study found that paced breathing also uses neural networks beyond the brain stem that are tied to emotion, attention, and body awareness. By tapping into these networks using the breath, we gain access to a powerful tool for regulating our responses to stress.

Your brain on paced breathing

In this study, researchers at the Feinstein Institute for Medical Research wanted to better understand how the brain responds to different breathing exercises. They recruited six adults already undergoing intracranial EEG monitoring for epilepsy. (EEG monitoring involves placing electrodes directly onto the brain to record electrical activity and see where seizures originate.) These adults were asked to take part in three breathing exercises while their brains were being monitored.

In the first exercise, participants rested with their eyes open for about eight minutes while breathing normally. They then sped up their breath to a rapid rate for just over two minutes, while breathing through the nose, then slowed back down to regular breathing. They repeated this cycle eight times.

In the next exercise, participants counted how many times they inhaled and exhaled for two-minute intervals, and reported how many breaths they’d taken. Researchers monitored how many breaths participants took during each interval, noting when responses were correct and incorrect.

Lastly, participants completed an attention task while wearing a device that monitored their breathing cycle. In it, they viewed a video screen containing black circles in different fixed locations. They were asked to press one of four keyboard keys as quickly as possible when they saw one of the circles change from black to white.

At the end of the study, researchers looked to see how participants’ breathing rates varied across different tasks and noted whether their brain activity changed depending on which task they were doing. They found that breathing affects brain regions including the cortex and midbrain more widely than previously thought.

Managing stress: Is it all in the breath?

What they found was increased activity across a network of brain structures, including the amygdala, when participants breathed rapidly. Activity in the amygdala suggests that quick breathing rates may trigger feelings like anxiety, anger, or fear. Other studies have shown that we tend to be more attuned to fear when we’re breathing quickly. Conversely, it may be possible to reduce fear and anxiety by slowing down our breath.

The present study also identified a strong connection between participants’ intentional (that is, paced) breathing and activation in the insula. The insula regulates the autonomic nervous system and is linked to body awareness. Prior studies have linked intentional breathing to posterior insular activation, suggesting that paying particular attention to the breath may increase awareness of one’s bodily states—a key skill learned in practices like yoga and meditation.

Finally, researchers noted that when participants accurately tracked their breath, both the insula and the anterior cingulate cortex, a region of the brain involved in moment-to-moment awareness, were active.

All told, the results of this study support a link between types of breathing (rapid, intentional, and attentional) and activation in brain structures involved in thinking, feeling, and behavior. This raises the possibility that particular breathing strategies may be used as a tool to help people to manage their thoughts, moods, and experiences.

This article was originally published on Mindful.org, a nonprofit dedicated to inspiring, guiding, and connecting anyone who wants to explore mindfulness. View the original article .

About the Author

B Grace Bullock

B Grace Bullock, Ph.D. , is a psychologist, organizational consultant, research scientist, educator, author, and motivational speaker. She has spent the past two decades teaching and studying physiological and psychological interventions that foster resilience and support healthy relationships and systems, and is the author of the acclaimed book, Mindful Relationships: Seven Skills for Success—Integrating the Science of Mind, Body and Brain .

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Breath Research

Exhaled breath is dynamic and its molecular profile changes during exhalation. The first part of exhaled breath is composed of the molecules that were present in the inhaled gas contained in the anatomic dead space. As the process of exhalation continues, the breath profile is defined by molecules derived from the oral cavity and the airways. Monitoring the concentration of carbon dioxide in the breath can be used to follow the progress of exhalation. When the concentration of carbon dioxide plateaus this portion of exhaled breath is known as end-tidal breath.

The molecular profile of end-tidal breath is defined by the concentrations and identities of the volatiles present in blood. The sources of the volatiles in blood are: molecules and/or their metabolites that have been inhaled (exposome), or have entered the bloodstream  via  the skin (exposome), have entered the bloodstream from ingested foods or beverages (metabolome); and molecules produced by foreign cells (viruses, bacteria, fungi, and yeasts) (microbiome) or by tissues in the body including the mouth, nose, sinuses, airway and the gastrointestinal tract (human metabolome). The majority of mixed-expired breath (99.995%) consists of nitrogen (78%), oxygen (13%), carbon dioxide (5%), water vapor (4%), and the inert gases, and the remainder (<50 ppmv) is a mixture of as many as 1000 different compounds. The rates of excretion of molecules in breath are directly related to rates of ventilation and cardiac output. The physical and chemical properties of molecules also affect their rates of excretion. If a molecule is lipid soluble, it could be stored in tissues not well perfused by blood, such as adipose tissue, and be released into breath more slowly than a different molecule with hydrophilic properties that is not lipid stored.

In general, the concentrations of endogenously produced molecules in breath are lower than the concentrations of molecules from exogenous sources. Unique molecules in breath can only originate from the ingestion, inhalation, or dermal absorption of exogenous substances or be metabolically produced by foreign cells (bacteria, viruses, or eukaryotic organisms). Normal cellular biochemistry can only be induced or suppressed by abnormal physiology and although disease states may appear to be producing unique molecules these results are only a reflection of the detection limit of the analytical method.

Collection of representative breath samples under controlled conditions is an  a priori  requirement for successful breath research. Ideally, breath should be sampled when the concentration of carbon dioxide reaches a plateau (end-tidal phase) and it is important that the person providing the sample (e.g., the patient) does not hyperventilate. Normally, the depth and frequency of breathing are under autonomic control. However, when the patient is asked to provide a breath sample this action invariably results in a change from autonomic breathing to conscious breathing. Standardized breath sampling methods or guidelines on best practices do not exist, but endeavors are currently underway to establish a common consensus, as will be disseminated via this website in due course.

Many of the modern analytical methods based upon spectroscopy, mass spectrometry, electrochemistry and chromatography have sufficient speed, sensitivity and selectivity to allow real-time breath analyses to be performed on a single breath. Standardized breathing protocols or guidelines on best practices do not exist, but endeavors are currently underway to establish a common consensus, as will be disseminated via this website in due course.

If comparisons of the results of breath analysis are to be used to study therapeutic intervention or to compare different study subjects, it is important to normalize concentrations of breath molecules to oxygen consumption or carbon dioxide production.

The use of breath for diagnosing disease will first require that the concentration profiles of breath molecules for normal healthy human subjects be established and these studies should include such variables as age, gender, ethnicity and body mass index. In order to recognize potential confounders, well-described cohorts of participants identified as “healthy” or “diseased” will need to provide breath samples that are evaluated for validity and reproducibility. Ideally, control subjects will be matched to the disease group for better comparability. A recent direction has been to use partners of patients, who are typically of similar age and, critically, generally share domestic exposure history with the patient, thereby reducing the likelihood of exogenous confounders being falsely attributed to disease.

• Breath Analysis in Clinical Use
• Challenges in Breath Research

IABR Membership

Become a member of the International Association of Breath Research and help to support the association. Members in good-standing will be eligible for a reduced registration fee for the official IABR Breath Summit conferences.

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https://www.nist.gov/news-events/news/2023/04/jilas-frequency-comb-breathalyzer-detects-covid-19-excellent-accuracy

JILA’s Frequency Comb Breathalyzer Detects COVID-19 With Excellent Accuracy

JILA researchers have upgraded a breathalyzer based on Nobel Prize-winning frequency-comb technology and combined it with machine learning to detect SARS-CoV-2 infection in 170 volunteer subjects with excellent accuracy. Their achievement represents the first real-world test of the technology’s capability to diagnose disease in exhaled human breath.

Frequency comb technology has the potential to non-invasively diagnose more health conditions than other breath analysis techniques while also being faster and potentially more accurate than some other medical tests. Frequency combs act as rulers for precisely measuring different colors of light, including the infrared light absorbed by molecules.

Human breath contains more than 1,000 different trace molecules, many of which are correlated with specific health conditions. JILA’s frequency comb breathalyzer identifies chemical signatures of molecules based on exact colors and amounts of infrared light absorbed by a sample of exhaled breath.

Back in 2008 , Jun Ye and colleagues at JILA demonstrated the world’s first frequency comb breathalyzer, which measured the absorption of light in the near-infrared part of the optical spectrum. In 2021 they achieved a thousandfold improvement in detection sensitivity by extending the technique to the mid-infrared spectral region, where molecules absorb light much more strongly. This enables some breath molecules to be identified at the parts-per-trillion level where those with the lowest concentrations tend to be present.

The added benefit to this study was the use of machine learning. Machine learning — a form of artificial intelligence (AI) — processes and analyzes a massive, complex mélange of data from all the breath samples as measured by 14,836 comb “teeth,” each representing a different color or frequency to create a predictive model to diagnose disease.

“Molecules increase or decrease in their concentrations when associated with specific health conditions. Machine learning analyzes this information, identifies patterns and develops reliable criteria we can use to predict a diagnosis,” said Qizhong Liang, a graduate student in the Jun Ye group, who is lead author of a new paper presenting the findings.

JILA is jointly operated by the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder (CU Boulder). The research was conducted on breath samples collected from 170 CU Boulder students and staff from May 2021 to January 2022. Approximately half of the volunteers tested positive for COVID-19 with standard PCR tests. The other half of the subjects tested negative. The young study group had a median age of 23 years old, and all were above 18 years old. The general campus population was more than 90% vaccinated.

“I do think that this comb technique is superior to anything out there,” NIST/JILA Fellow Jun Ye said. “The basic point is not just the detection sensitivity, but the fact that we can generate a far greater amount of data, or breath markers, really establishing a whole new field of ‘comb breathomics’ with the help of AI. With a database, we can then use it to search and study many other physiological conditions for human beings and to help advance the future of healthcare.”

The JILA comb breathalyzer method demonstrated excellent accuracy for detecting COVID by using machine learning algorithms on absorption patterns to predict SARS-CoV-2 infection. H 2 O (water), HDO (semi-heavy water), H 2 CO (formaldehyde), NH 3 (ammonia), CH 3 OH (methanol), and NO 2 (nitrogen dioxide) were identified as discriminating molecules for detection of SARS-CoV-2 infection.

The team measured the accuracy of their results by creating a data graph comparing their predictions of COVID-19 against the PCR test results (which, it should be noted, have high but not perfect accuracy). On the graph, they computed a quantity known as the “area under the curve” (AUC). An AUC of 1, for example, would be expected for perfectly discriminating between ambient air and exhaled breath. An AUC of 0.5 would be expected for making random guesses on whether the individuals were born on odd or even months. The researchers measured an AUC of 0.849 for their COVID-19 predictions. An AUC of 0.8 or greater for medical diagnostic data is considered “ excellent ” accuracy.

In the future, the researchers could further increase the accuracy by expanding the spectral coverage, analyzing the patterns with more powerful AI techniques, and measuring and analyzing additional molecules, which could include the SARS-CoV-2 virus itself. Researchers would need to build a database of the specific IR colors absorbed by the virus (its spectral “fingerprint”) to potentially measure viral concentrations in the breath.

The researchers also identified significant differences in breath samples based on tobacco use and a variety of gastrointestinal symptoms such as lactose intolerance. This suggests broader capability of the technique for diagnosing different sets of diseases.

The research was published in the Journal of Breath Research , the official Journal of the International Association for Breath Research.

The researchers plan further studies to try to diagnose other conditions such as chronic obstructive pulmonary disease, the third leading cause of death worldwide according to the World Health Organization. The researchers have also recently boosted the comb breathalyzer’s diagnostic power by expanding the spectral coverage to detect additional molecules. They plan to employ additional AI approaches such as deep learning to improve its disease-detection abilities. Efforts are already under way to miniaturize and simplify the technology to make it portable and easy to use in hospitals and other care settings.

Ye said there is interest from the medical community in seeing the comb breathalyzer developed further and commercialized. Approval by the U.S. Food and Drug Administration (FDA) would be needed before the technology could be used in medical settings.

The most prevalent analytical technique in breath research now is gas chromatography combined with mass spectrometry, which can detect hundreds of exhaled molecules but works slowly, typically requiring tens of minutes. Its use of chemical process also unavoidably alters breath components and presents analytical challenges to identify breath profiles accurately. Frequency comb technology measures breath molecules in a non-destructive and real time manner and can promote a more accurate and repeatable determination of exhaled breath contents.

The research is supported by the Air Force Office of Scientific Research, the Department of Energy, the National Science Foundation, and NIST.

Paper: Q. Liang, Y-C. Chan, J. Toscano, K.K. Bjorkman, L.A. Leinwand, R. Parker, E.S. Nozik, D.J. Nesbitt and J. Ye. Breath analysis by ultra-sensitive broadband laser spectroscopy detects SARS-CoV-2 infection. Journal of Breath Research. Published 5 April 2023. DOI: 10.1088/1752-7163/acc6e4

Health and Wellness

Infographic text – commonly reported long covid symptoms.

• Post Exertional Malaise
• Chronic Pain

Mental Health

• Mood Changes

Respiratory

• Shortness of Breath
• Difficulty Breathing

Musculoskeletal

• Muscle Aches

Nervous System

• Cognitive Issues
• Memory Loss
• Loss of Taste or Smell
• Difficulty Sleeping
• Excessive Thirst

Cardiovascular

• Heart Palpitations
• Irregular Heartbeat
• Blood Clots

Gastrointestinal

• Constipation
• Abdominal Pain
• Loss of Appetite
• Changes in Color

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Mouthrinse (Mouthwash)

• There are two main types of mouthrinse: cosmetic and therapeutic.
• Therapeutic mouthrinses are available both over-the-counter and by prescription, depending on the formulation.
• There are therapeutic mouthrinses that help reduce or control plaque, gingivitis, bad breath, and tooth decay.
• Children younger than the age of 6 should not use mouthrinse, unless directed by a dentist, because they may swallow large amounts of the liquid inadvertently.
• A company earns the ADA Seal of Acceptance  by providing scientific evidence that demonstrates the safety and efficacy of its product, which the ADA Council on Scientific Affairs carefully evaluates according to objective requirements.

While not a replacement for daily brushing and flossing, use of mouthrinse (also called mouthwash) may be a helpful addition to the daily oral hygiene routine for some people. Like interdental cleaners, mouthrinse offers the benefit of reaching areas not easily accessed by a toothbrush. The question of whether to rinse before or after brushing may depend on personal preference; however, to maximize benefit from the oral care products used, manufacturers may recommend a specific order for their use, depending on ingredients.  For example, some dentifrice ingredients (like calcium hydroxide or aluminum hydroxide) can form a complex with fluoride ions and reduce a mouthrinse’s effectiveness. Therefore, vigorous rinsing with water may be recommended after brushing and before rinsing if these ingredients are present. 1

Mouthrinse is not recommended for children younger than 6 years of age unless directed by a dentist.  Swallowing reflexes may not be well developed in children this young, and they may swallow large amounts of the mouthrinse, which can trigger adverse events—like nausea, vomiting, and intoxication (due to the alcohol content in some rinses). 1, 2 Check the product label for specific precautions and age recommendations.

Broadly speaking, there are two types of mouthrinse: cosmetic and therapeutic.  Cosmetic mouthrinses may temporarily control bad breath and leave behind a pleasant taste, but have no chemical or biological application beyond their temporary benefit. For example, if a product doesn’t kill bacteria associated with bad breath, then its benefit is considered to be solely cosmetic. Therapeutic mouthrinses, by contrast, have active ingredients intended to help control or reduce conditions like bad breath, gingivitis, plaque, and tooth decay.

Active ingredients that may be used in therapeutic mouthrinse include:

• cetylpyridinium chloride;
• chlorhexidine;
• essential oils;

Cetylpyridinium chloride may be added to reduce bad breath. 3   Both chlorhexidine and essential oils can be used to help control plaque and gingivitis. 4, 5 Fluoride is a proven agent in helping to prevent decay. 6 Peroxide is present in several whitening mouthrinses. 1 Therapeutic mouthrinse is available both over-the-counter and by prescription, depending on the formulation.  For example, mouthrinses containing essential oils are available in stores, while those containing chlorhexidine are available only by prescription.

Some of the conditions mouthrinses are designed to address are discussed in the following sections.

Alveolar Osteitis (Dry Socket)

Alveolar osteitis (AO), also known as dry socket, is a common postoperative condition following dental extraction procedures, particularly those of the third molar. 7 AO occurs when the fibrin clot that forms following extraction is dislodged. AO usually results in intense pain in and around the extraction site 2 to 3 days after the procedure. A recent systematic review and meta-analysis of 18 trials 7 has shown chlorhexidine, without the use of antibiotics, to be effective for lowering the risk of AO following third molar extractions.  A moderate, but statistically not significant, increase in efficacy was seen in the gel formulation compared with the rinse formulation; however, the review could not recommend a specific dosing regimen. Studies included in the review reported minor, nonclinical reactions to chlorhexidine, including staining of teeth, dentures, and tongue, and altered taste.

Oral Malodor (Bad Breath)

Volatile sulfur compounds (VSCs) are the major contributing factor to oral malodor or bad breath. They arise from a variety of sources (e.g., breakdown of food, dental plaque and bacteria associated with oral disease). 3 Cosmetic mouthrinses can temporarily mask bad breath and provide a pleasing flavor, but do not have an effect on bacteria or VSCs. Mouthrinses with therapeutic agents like antimicrobials, however, may be effective for more long-term control of bad breath. Antimicrobials in mouthrinse formulations include chlorhexidine, chlorine dioxide, cetylpyridinium chloride, and essential oils (e.g., eucalyptol, menthol, thymol, and methyl salicylate). Other agents used in mouthrinses to inhibit odor-causing compounds include zinc salts, ketone, terpene, and ionone. 1 Although the combination of chlorhexidine and cetylpyridinium chloride plus zinc lactate has been shown to significantly reduce bad breath, it also may significantly contribute to tooth staining. 3, 8

Plaque and Gingivitis

When used in mouthrinses, antimicrobial ingredients like cetylpyridinium chloride, chlorhexidine, and essential oils have been shown to help reduce plaque and gingivitis when combined with daily brushing and flossing. 5, 9  While some studies have found that chlorhexidine achieved better plaque control than essential oils, no difference was observed with respect to gingivitis control. Cetylpyridinium chloride and chlorhexidine may cause brown staining of teeth, tongue, and/or restorations. 4

Preprocedural Mouthrinse

Some dental equipment and procedures, including ultrasonic scalers, air polishing, air-water syringe and tooth polishing with air turbine handpieces or air abrasion, generate aerosols, a mix of liquid and solid particles. 10, 11 Aerosols can remain airborne for up to four hours before settling on surrounding surfaces. 12 In addition to settling on environmental surfaces, aerosols containing microorganisms can be inhaled by dental care providers, posing a risk for disease transmission. 11 Respiratory diseases associated with aerosols include influenza, and tuberculosis, as well as COVID-19 SARS-CoV-2.1 10, 11

Research suggests that having a patient use a mouthrinse prior to treatment may reduce the amount of aerosolized microorganisms. However, there is no evidence that preprocedural mouthrinse protects against clinical disease among dental staff. 11

Bacteriocidal effect of preprocedural mouthrinses . The evidence suggests that preprocedural mouthrinse is effective at reducing bacterial contamination in dental aerosols. 12 Certain antimicrobial rinse solutions used from 30 seconds to 2 minutes versus water or no rinse effectively reduced aerosol contamination produced during periodontal prophylaxis. 12  For example. chlorhexidine (either 0.12 or 0.2%) is an effective antimicrobial solution for this purpose. 12  One drawback, however, is that chlorhexidine can cause tooth staining, supragingival calculus formation, and a change in taste sensation. 13 Researchers also, though, have found comparable performance between chlorhexidine and cetylpyridinium chloride as a preprocedural rinse in reducing bacterial load in aerosols. 11

Virucidal effect of preprocedural mouthrinses . Although little clinical data have been collected , 12 one small study found that preprocedural rinses, including normal saline, reduced SARS-CoV-2 viral load in saliva. 14

One review of four in vitro studies, however, found that a preprocedural rinse with chlorhexidine was effective at reducing viral load. 13 Essential oils also were shown to have antiviral properties against enveloped viruses. 13

Overall, there is a need for additional research concerning the role of preprocedural mouthrinses in preventing viral infections. 12

Tooth Decay

Fluoride ions, which promote remineralization, may be provided by certain mouthrinses. A Cochrane systematic review found that regular use of fluoride mouthrinse reduced tooth decay in children, regardless of exposure to other sources of fluoride (i.e., fluoridated water or toothpaste containing fluoride). 15

Topical Pain Relief

Mouthrinses that offer pain relief most commonly contain topical local anesthetics such as lidocaine, benzocaine/butamin/tetracaine hydrochloride, dyclonine hydrochloride, or phenol. 1 In addition, sodium hyaluronate, polyvinylpyrrolidine and glycyrrhetinic acid may act as a barrier to relieve pain secondary to oral lesions, like aphthous ulcers. 1

Mouthrinse may contribute to extrinsic stain reduction when either carbamide peroxide or hydrogen peroxide are among the active ingredients. Products that rely on carbamide peroxide typically contain 10 percent carbamide peroxide and may be dispensed by dentists to their patients for use at home. 16 Mouthrinses that claim to whiten teeth also may contain 1.5 to 2 percent hydrogen peroxide. 1  One study found that 12 weeks' use of mouthrinse containing hydrogen peroxide in this concentration range achieved similar color alteration as that achieved by 2 weeks' use of 10 percent carbamide peroxide whitening gel. 17

Xerostomia is a reduction in the amount of saliva bathing the oral mucous membranes. Since the lack of saliva increases the risk of caries, a fluoride-containing mouthrinse may be helpful to those managing this problem. However, since alcohol can be drying, it may be prudent to recommend an alcohol-free mouthrinse. 18 Mouthrinses containing enzymes, cellulose derivatives and/or animal mucins can mimic the composition and feel of saliva and may provide additional relief from symptoms associated with xerostomia. 1

Oral Cancer Concern

Alcohol consumption as well as alcohol and tobacco use are known risk factors for head and neck cancers. 19 Resulting from this has been the question of whether use of alcohol-containing mouthrinse increases risk of these cancers. 20 A recent systematic review and meta-analysis failed to find an association between mouthrinse use and oral cancer, use of alcohol-containing mouthrinse and oral cancer, or mouthrinse dose response and oral cancer. 21

• Use prescription mouthrinses as directed (i.e., dose, frequency, time in mouth). If a dose is missed, use the rinse as soon as possible; doubling the dose will have no therapeutic effect. 1
• With over-the-counter products, look for mouthrinses that have the ADA Seal of Acceptance . The Seal shows that a company has provided data demonstrating that a product is safe and effective for the purpose claimed.
• Using a mouthrinse does not take the place of optimal brushing and flossing.  Mouthrinses may offer additional benefit in terms of reducing the risk of bad breath, cavities, or gum disease; or for relief of dry mouth or pain from oral sores.

Look for the ADA Seal—your assurance that the product has been objectively evaluated for safety and efficacy by an independent body of scientific experts, the ADA Council on Scientific Affairs. A company earns the ADA Seal for mouthrinse by producing scientific evidence demonstrating the safety and efficacy of its product, which is evaluated according to the objective requirements related to their claims.

Manufacturers of all types of mouthrinse who apply for the Seal must demonstrate that their products adhere to FDA regulations and meet the ANSI/ADA or ISO Standards for Oral Care products (wherever applicable). To qualify for the Seal of Acceptance, the company must demonstrate that their product meets applicable ADA Seal requirements, and must provide safety and efficacy data, to support the claims associated with their product. For example:

• Manufacturers of mouthrinses that contain fluoride for reducing decay must demonstrate the total concentration of fluoride, and other parameters as per the standards. For additional active agents, or inactive agents that might be expected to interfere with fluoride, clinical anticaries studies may be required.
• Manufacturers that claim control of gingivitis must substantiate this assertion by demonstrating statistically significant reduction in gingival inflammation and plaque formation or pathogenicity.
• Manufacturers that claim their mouthrinse controls bad breath must provide data demonstrating that it reduces oral malodor when compared to a control over a meaningful period of time.
• Manufacturers of mouthrinses designed to alleviate dry mouth must provide data showing that the product is safe and effective in temporarily relieving dry mouth symptoms, when used as directed.
• Mariotti AJ, Burrell, K.H. Mouthrinses and dentifrices. 5th ed. Chicago: American Dental Association and Physician's Desk Reference, Inc.; 2009.
• Weyant RJ, Tracy SL, Anselmo TT, et al. Topical fluoride for caries prevention: executive summary of the updated clinical recommendations and supporting systematic review. J Am Dent Assoc 2013;144(11):1279-91.
• Blom T, Slot DE, Quirynen M, Van der Weijden GA. The effect of mouthrinses on oral malodor: a systematic review. Int J Dent Hyg 2012;10(3):209-22.
• Van der Weijden FA, Van der Sluijs E, Ciancio SG, Slot DE. Can chemical mouthwash agents achieve plaque/gingivitis control? Dent Clin North Am 2015;59(4):799-829.
• Araujo MW, Charles CA, Weinstein RB, et al. Meta-analysis of the effect of an essential oil-containing mouthrinse on gingivitis and plaque. J Am Dent Assoc 2015;146(8):610-22.
• Fejerskov O, Thylstrup A, Larsen MJ. Rational use of fluorides in caries prevention. A concept based on possible cariostatic mechanisms. Acta Odontol Scand 1981;39(4):241-9.
• Rodriguez Sanchez F, Rodriguez Andres C, Arteagoitia Calvo I. Does chlorhexidine prevent alveolar osteitis after third molar extractions? Systematic review and meta-analysis. J Oral Maxillofac Surg 2017.
• Fedorowicz Z, Aljufairi H, Nasser M, Outhouse TL, Pedrazzi V. Mouthrinses for the treatment of halitosis. Cochrane Database Syst Rev 2008(4):CD006701.
• Sharma N, Charles CH, Lynch MC, et al. Adjunctive benefit of an essential oil-containing mouthrinse in reducing plaque and gingivitis in patients who brush and floss regularly: a six-month study. J Am Dent Assoc 2004;135(4):496-504.
• Harrel SK, Molinari J. Aerosols and splatter in dentistry: a brief review of the literature and infection control implications. J Am Dent Assoc 2004;135(4):429-37.
• Marui VC, Souto MLS, Rovai ES, et al. Efficacy of preprocedural mouthrinses in the reduction of microorganisms in aerosol: A systematic review. J Am Dent Assoc 2019;150(12):1015-26.e1.
• Mohd-Said S, Mohd-Dom TN, Suhaimi N, Rani H, McGrath C. Effectiveness of Pre-procedural Mouth Rinses in Reducing Aerosol Contamination During Periodontal Prophylaxis: A Systematic Review. Front Med (Lausanne) 2021;8:600769.
• Moosavi MS, Aminishakib P, Ansari M. Antiviral mouthwashes: possible benefit for COVID-19 with evidence-based approach. J Oral Microbiol 2020;12(1):1794363.
• Chaudhary P, Melkonyan A, Meethil A, et al. Estimating salivary carriage of severe acute respiratory syndrome coronavirus 2 in nonsymptomatic people and efficacy of mouthrinse in reducing viral load: A randomized controlled trial. J Am Dent Assoc 2021;152(11):903-08.
• Marinho VC, Higgins JP, Logan S, Sheiham A. Topical fluoride (toothpastes, mouthrinses, gels or varnishes) for preventing dental caries in children and adolescents. Cochrane Database Syst Rev 2003(4):CD002782.
• Hasson H, Ismail AI, Neiva G. Home-based chemically-induced whitening of teeth in adults. Cochrane Database Syst Rev 2006(4):CD006202.
• Torres CR, Perote LC, Gutierrez NC, Pucci CR, Borges AB. Efficacy of mouth rinses and toothpaste on tooth whitening. Oper Dent 2013;38(1):57-62.
• Kerr AR, Corby PM, Kalliontzi K, McGuire JA, Charles CA. Comparison of two mouthrinses in relation to salivary flow and perceived dryness. Oral Surg Oral Med Oral Pathol Oral Radiol 2015;119(1):59-64.
• Chi AC, Day TA, Neville BW. Oral cavity and oropharyngeal squamous cell carcinoma - an update. CA Cancer J Clin 2015;65(5):401-21.
• Weaver A, Fleming SM, Smith DB. Mouthwash and oral cancer: carcinogen or coincidence? J Oral Surg 1979;37(4):250-3.
• Gandini S, Negri E, Boffetta P, La Vecchia C, Boyle P. Mouthwash and oral cancer risk quantitative meta-analysis of epidemiologic studies. Ann Agric Environ Med 2012;19(2):173-80.

What products have earned the ADA Seal of Acceptance?

Get a Complete List of ADA Accepted Mouthrinses

Additional Resources

• ADA Center for Evidence-based Dentistry Treatment Guidelines: Professionally-applied and Prescription-strength, Home-use Topical Fluoride Agents for Caries Prevention Clinical Practice Guideline (2013)
• ADA MouthHealthy: Mouthwash
• JADA “For the Patient” pages: Targeting bad breath , Managing dry mouth , Sealing the Deal: Buying Products That Have the ADA Seal of Acceptance
• Information Sheet on pH of Home Oral Care Products

Last Updated: December 1, 2021

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• Cell Rep Med
• v.4(1); 2023 Jan 17

Brief structured respiration practices enhance mood and reduce physiological arousal

Melis yilmaz balban.

1 Department of Neurobiology, School of Medicine, Stanford University, Stanford, CA 94305, USA

2 Department of Psychiatry & Behavioral Sciences, School of Medicine, Stanford University, Stanford, CA 94305, USA

Manuela M. Kogon

3 Stanford Center for Integrative Medicine, Stanford Health Care, Palo Alto, CA 94304, USA

4 Department of Bioengineering, School of Engineering and School of Medicine, Stanford University, Stanford, CA 94305, USA

Bita Nouriani

Jamie m. zeitzer.

5 Mental Illness Research Education and Clinical Center, VA Palo Alto Health Care Service, Palo Alto, CA 94304, USA

David Spiegel

6 Center for Stress and Health, School of Medicine, Stanford University, Stanford, CA 94305, USA

Andrew D. Huberman

7 Department of Ophthalmology, School of Medicine, Stanford University, Stanford, CA 94305, USA

8 BioX, School of Medicine, Stanford University, Stanford, CA 94305, USA

Associated Data

• De-identified raw human physiology and survey data have been deposited at Dryad repository ( https://datadryad.org/ ) and are publicly available as of the date of publication. Accession numbers are listed in the key resources table .
• All original code has been deposited at Zenodo and is publicly available as of the date of publication. DOIs are listed in the key resources table .
• Any additional information required to reanalyze the data reported in this paper is available from the lead contact upon request.

Controlled breathwork practices have emerged as potential tools for stress management and well-being. Here, we report a remote, randomized, controlled study ( {"type":"clinical-trial","attrs":{"text":"NCT05304000","term_id":"NCT05304000"}} NCT05304000 ) of three different daily 5-min breathwork exercises compared with an equivalent period of mindfulness meditation over 1 month. The breathing conditions are (1) cyclic sighing, which emphasizes prolonged exhalations; (2) box breathing, which is equal duration of inhalations, breath retentions, and exhalations; and (3) cyclic hyperventilation with retention, with longer inhalations and shorter exhalations. The primary endpoints are improvement in mood and anxiety as well as reduced physiological arousal (respiratory rate, heart rate, and heart rate variability). Using a mixed-effects model, we show that breathwork, especially the exhale-focused cyclic sighing, produces greater improvement in mood (p < 0.05) and reduction in respiratory rate (p < 0.05) compared with mindfulness meditation. Daily 5-min cyclic sighing has promise as an effective stress management exercise.

Graphical abstract

• • Daily 5-minute breathwork and mindfulness meditation improve mood and reduce anxiety
• • Breathwork improves mood and physiological arousal more than mindfulness meditation
• • Cyclic sighing is most effective at improving mood and reducing respiratory rate

In a remotely conducted randomized controlled trial, Yilmaz Balban et al. study the psychophysiological effects of controlled breathwork compared with mindfulness meditation. Breathwork produces greater improvement in mood and reduction in respiratory rate, while both result in reduction in negative emotion including state anxiety.

Introduction

Breathing is a life-sustaining bodily function, facilitating oxygenation and carbon dioxide disposal, but scientific studies on its significance for the mind-body connection have been limited. Embedded in ancient practices for centuries, breathwork has emerged as an intervention due to its reported health benefits. The COVID-19 pandemic highlighted the importance of simple, fast-acting, and cost-effective techniques to address widespread physical and mental health challenges and limited access to health care. While the neurobiology of breath has been studied both in animals and humans, 1 little comparative data exist on the effects of different breathing techniques or the amount of breathing exercise that must be performed to produce those effects.

The pattern and depth of breathing have direct physiological impact on oxygenation level, heart rate, ventilation, and blood pressure. 2 Slow breathing at a rate of six breaths per minute reduces chemoreceptor reflex response to hypercapnia and hypoxia compared with spontaneous respiration at 15 breaths per minute. 3 Impairment of baroreceptor reflex sensitivity plays a role in the etiology of hypertension, and how we breathe has numerous other major health implications. Heart rate and blood pressure decrease with slow breath in patients with essential hypertension compared with higher-frequency breathing. 4 Breathing training has also been shown to improve quality of life for asthmatics and to decrease use of bronchodilators. 5 Furthermore, there is evidence that nasal breathing affects the CNS differently than mouth breathing. While nasal breathing synchronizes electrical activity in the olfactory cortex as well as amygdala and hippocampus, mouth breathing does not, 6 which has implications for stress management and treatment of anxiety. Moreover, the mere act of inhaling has been shown to increase alertness levels and learning in humans. 7

It is also clear that different emotional and cognitive states alter the depth and frequency of breathing, 8 , 9 , 10 , 11 , 12 which likewise impacts emotional state, in part by regulation of carbon dioxide levels. 13 , 14 , 15 , 16 , 17 There is growing evidence that brain-body states, ranging from sleep to stress to physical activity to meditation, can help people buffer and better manage stressors. A review of Yogic breathing practices reported increased feelings of peacefulness, improved reaction time and problem solving, decreased anxiety, and reduction of mind wandering and intrusive thoughts. 18 , 19

A central theme of many Yogic and meditative practices is the inclusion of deliberate patterns of breathing. Despite the mounting evidence in favor of the benefits of these practices for overall health and wellbeing, 20 it is not well understood how different types of breathing per se impact mood and physiology, and how those effects compare with the brief practice of mindfulness meditation. This common practice with proven mental health benefits 21 , 22 , 23 , 24 involves passive observation of breath and is typically practiced daily for 20-min (or more) sessions. 22

There are several ways in which voluntary controlled breathing exercises differ from the practice of mindfulness meditation. Controlled breathing directly influences respiratory rate, which can cause more immediate physiological and psychological calming effects by increasing vagal tone during slow expiration. While mindfulness meditation might decrease sympathetic tone in the long run, 25 that is not its primary purpose or an expected acute effect. Mindfulness meditation involves bringing attention to the breath for the purpose of increasing awareness of the present moment. Thus, we hypothesized that direct modulation of the physiological state provided by controlled breathing could produce more potent and acute mental and physical relaxation. Additionally, interventions that act faster acutely encourage adherence because people feel better during the intervention. Thus, we hypothesized that breathwork might provide longer lasting benefits than mindfulness meditation due to improvements in daily mood and better adherence. Finally, breathwork exercises provide a sense of direct control over one’s physiology as opposed to passively attending to the presence of one’s breath during mindfulness meditation. This enhanced sense of control could reduce anxiety quickly as perceived loss of control is a hallmark of anxiety. 26 , 27 Thus, our primary hypothesis for this study was that voluntarily controlled breathing exercises would have differential effects on mood and physiology compared with mindfulness meditation, which involves passive observation of the breath. Accordingly, we hypothesized that all three breathing interventions would be more effective in reducing anxiety and regulating physiology than mindfulness meditation.

One of the main differentiators of common breathing techniques is the emphasis on relative duration and intensity of inhales versus exhales. “Sighing,” characterized by deep breaths followed by extended, relatively longer exhales, has been associated with psychological relief, shifts in autonomic states, and resetting of respiratory rate. 8 , 28 , 29 , 30 “Box breathing” or “tactical breathing,” on the other hand, is characterized by equal inhale and hold and exhale ratios and has been used by members of the military for stress regulation and performance improvement. 30 , 31 , 32 “Hyperventilation with retention” is characterized by an emphasis on inhalations of longer duration and relatively greater intensity than exhales. 33 The type of breathing associated with hyperventilation has been linked with chronic anxiety and even panic when it emerges reflexively but has also been shown to have therapeutic effects when done deliberately in a controlled way. 34 There is still limited understanding of how specific breathing mechanics (i.e., inhale-exhale ratios) influence autonomic activity and wellness. 8 , 35

Inhales increase heart rate and exhales decrease heart rate via respiratory sinus arrhythmia 36 —a normal phenomenon that relates to the effects of breathing on intrathoracic pressure, diaphragmatic movement, heart volume/blood flow rates, and compensatory shifts in vagal activation. 37 We sought to explore how inhale-emphasized (longer inhales) versus exhale-emphasized (longer exhales) versus balanced inhale-exhale breathing impact physiology and subjective measures of anxiety. We also sought to compare these with mindfulness meditation, which emphasizes passive observation of natural breathing with no active control. Finally, we sought to determine if as little as 5 min per day of deliberate breathing practice can cause significant shifts in autonomic tone and well-being.

Secondarily, we wanted to investigate if breathing practices with different inhale-exhale ratios have differential effects on physiology and psychological measures. We hypothesized that breathing practices that place emphasis on the exhale versus the inhale portion of each breath would be more effective in reducing anxiety and improving well-being. Accordingly, we hypothesized that cyclic sighing would have more beneficial psychological and physiological effects than cyclic hyperventilation or box breathing.

In this study, we tested these two hypotheses by comparing mindfulness meditation with the breathwork groups, first combining all breathwork participants and then separately by subgroup if there was a main effect, on measures of mood, anxiety, resting heart rate, heart rate variability, respiration rate, and sleep ( Figures 1 A and 1B). Our understanding of the effects of breathing on the brain and body ought to allow specific science-supported breath practices to be designed in order to improve stress tolerance and sleep, enhance energy, focus, and creativity, and regulate emotional and cognitive states.

Study design

(A) Chart describing study design and the mindfulness meditation and three breathing exercises tested. n = number of participants enrolled in each group. Upward arrows indicate the inhales, downward arrows indicate the exhales, and horizontal arrows indicate breath holds. The corresponding numbers indicate the approximate ratios in time of the inhales, holds, and exhales. See also Figure S1 and Tables S1 and S2 .

(B) Timeline describing the study. Baseline measurements were collected between day −2 and 0. Baseline measurements were STAI trait anxiety and PROMIS sleep-related daytime disturbance scores. The same measures were collected at the end of the study between days 29 and 31 (post-study measures). Daily measures included ones collected before and after the exercises, including measures of state anxiety, positive affect (PANAS) and negative affect (PANAS), as well as daily average data from the WHOOP strap including resting heart rate (RHR), respiration rate, heart rate variability (HRV; root mean square of successive differences between normal heartbeats [RMSSD]), sleep efficiency, hours of sleep, and sleep score.

Subject participation

Of 140 potential participants who consented, 114 were invited to participate in the study. The primary reasons for attrition at this stage were due to pandemic-related reasons or loss of contact with the participants. See Figure S1 for a detailed participant flow diagram. The general ease of following instructions and performing the interventions and subjective experience of the interventions were assessed by an optional debriefing questionnaire at the end of the study. We found that 90% of the participants reported positive experiences during the exercises ( Table S2 ), while 10% reported negative experiences related to the exercises. In addition, 96% of the participants found video instructions “very easy” or “somewhat easy” and 74% found the interventions “very easy” or “somewhat easy.” More details of the results of the debriefing survey are presented in Table S2 . Participants in the mindfulness meditation group spent on average 6.16 ± 6.62 (mean over 28 days ± SD) minutes while breathwork groups spent on average 5.76 ± 5.32 (mean over 28 days ± SD) minutes on the intervention. On average, mindfulness meditation participants completed 17.71 ± 9.25 of the 28 days, and breathwork participants completed 19.61 ± 7.73 of the 28 days. There were no differences between the groups on the daily time spent or number of days spent on the interventions.

Both mindfulness meditation and breathwork groups showed significant reductions in state anxiety and negative affect and increases in positive affect.

We compared positive affect (positive and negative affect schedule [PANAS], range 10–50), negative affect (PANAS, range 10–50), and state anxiety (State-Trait Anxiety Inventory [STAI], range 20–80) scores on each participant before and after each breathwork protocol daily. Mindfulness meditation and breathwork groups both experienced an increase in daily positive affect ( Figures 2 A and S2 A–S2D). The average daily change per person in positive affect was 1.22 ± 2.34 for mindfulness meditation (p = 0.06) and 1.91 ± 3.38 for breathwork groups combined (p < 0.0001, 1.89 ± 3.76 for cyclic sighing [p = 0.025], 1.84 ± 3.24 for box breathing [p = 0.026], and 1.97 ± 3.21 for cyclic hyperventilation with retention [p = 0.003], where p values are based on a paired Wilcoxon test for before and after comparisons).

Effects of breathing exercises on daily pre- to post-change in subjective measures of anxiety and mood

(A–C) Line plot showing the average daily change in PANAS positive affect (A), PANAS negative affect (B), and STAI state anxiety (C) on days 1–28 in the mindfulness meditation and breathwork groups (average rate of attrition = 2.5 participants/day for breathwork, 0.7 participants/day for mindfulness meditation, error bars = SEM).

(D) Linear mixed-effects model to compare the daily psychological measures between the two types of protocols and estimate the effect of adherence to the protocol. Significant values are indicated in bold. (∗ = p < 0.05).

See also Figures S2 and S4 and Table S2 .

Both mindfulness meditation and breathwork groups had significant reductions in negative affect after the protocol compared with before ( Figures 2 B and S2 E–S2H). The average daily change per person in negative affect was −1.62 ± 1.91 for mindfulness meditation and −0.98 ± 1.39 for breathwork groups combined (−1.48 ± 1.69 for cyclic sighing, −0.83 ± 1.09 for box breathing, and −0.62 ± 1.14 for cyclic hyperventilation with retention [p < 0.0001 for all groups based on a paired Wilcoxon test]).

Similar to positive and negative affect, participants in both mindfulness meditation and breathwork groups had a significant reduction in state anxiety after the exercise compared with before the exercise when averaged across the 28 days ( Figures 2 C and S2 I–S2L). The average daily change per person in state anxiety was −3.95 ± 4.16 for mindfulness meditation and −3.03 ± 3.83 for all breathwork groups combined (−3.85 ± 4.88 for cyclic sighing, −3.75 ± 2.83 for box breathing, and −1.81 ± 2.97 for cyclic hyperventilation with retention [p < 0.0001 for all groups based on a paired Wilcoxon test]). As expected, there were no significant changes in trait anxiety in any of the groups, nor were there differences in trait anxiety change between the groups ( Figure S4 ).

Breathwork, specifically cyclic sighing, is more effective in increasing positive affect than is mindfulness meditation

We then examined if breathwork was more effective than mindfulness meditation in reducing anxiety and improving mood. To address this, we constructed a linear mixed-effects model with protocol type and “number of days on protocol” as the fixed effect and participants as the random effect predictors ( Figure 2 D). This model was used to assess the effect of protocol and effect of adherence on the daily changes in positive affect, negative affect, or state anxiety. The “day on protocol” term reflected for each day the number of days the subject had followed the protocol up to that day (see STAR Methods for more details). This term was added to account for the within-participant variance in the daily changes in mood and anxiety over time. There were no differences between the two groups in state anxiety and negative affect changes ( Figures 2 B–2D). However, the breathwork group had a notably higher increase in daily positive affect ( Figures 2 A and 2D). The breathwork group also had a significant interaction with the number of days on protocol, such that the daily positive affect increase was larger the more days subjects had been on the protocol ( Figures 2 A and 2D), suggesting an effect of adherence over time on the daily positive affect benefits.

On the basis of the increase in daily positive affect associated with breathwork, we then asked whether one or more of the specific breathwork groups accounted for the improvement compared with mindfulness meditation throughout the study. To address this, we compared each specific breathwork group with the mindfulness meditation group using the same mixed-effects modeling method. We found that the cyclic sighing group had a significantly higher increase in positive affect than those in the mindfulness meditation group ( Figures 3 , S2 A, and S2B). The other two breathwork groups were also higher than mindfulness meditation; however, this difference was not significant ( Figures 3 , S2 A, S2C, and S2D). Cyclic sighing also had a significant interaction with cumulative days on protocol compared with mindfulness meditation, suggesting that subjects benefited more from the exercise the more days they did it, an effect not observed in the other groups ( Figure 3 B).

Effects of breathing exercises on daily positive affect

(A) Line plot showing the average change in PANAS positive affect on days 1–28 in the mindfulness meditation and three individual breathwork groups (average rate of attrition = 0.7 participants/day for mindfulness meditation, 0.9 participants/day for cyclic sighing, 0.6 participants/day for box breathing, and 1.1 participants/day for cyclic hyperventilation, error bars = SEM).

(B) Linear mixed-effects model to predict the positive affect change and with four different groups and adherence (number of days on protocol) as fixed effects. Significant values are indicated in bold. (∗ = p < 0.05, ∗∗ = p < 0.01).

See also Figure S2 .

Overall, breathwork was more effective than mindfulness meditation in improving positive affect, an effect that got larger with more adherence to the protocol. Participants in the exhale-emphasized cylic sighing group had the highest increase in positive affect throughout the course of the 1-month study.

Breathwork produces a significantly greater reduction in respiratory rate compared with mindfulness meditation

To evaluate the change in physiological metrics, slopes of daily heart rate variability, resting heart rate, and respiratory rate over the period of the study were calculated for each participant and compared between mindfulness meditation and breathwork groups. The breathwork group had a significantly higher reduction in respiratory rate than the mindfulness meditation group ( Figure 4 A; p < 0.05). We then compared individual breathwork groups with mindfulness meditation and found that the reduction in respiratory rate in cyclic sighing was significantly different from mindfulness meditation ( Figure 4 B; p < 0.05). Interestingly, change in respiratory rate was negatively correlated with change in daily positive affect ( Figure S5 ; r = - 0.24, p < 0.05), suggesting that participants who showed the highest reduction in respiratory rate also showed the highest daily increase in positive affect over the course of the study ( Figure S5 ). No significant changes were found in heart rate variability or resting heart rate over the course of the study in either of the groups ( Figures 4 C and 4D). As a secondary analysis, we compared each breathwork group with mindfulness meditation and found no differences in changes in resting heart rate or heart rate variability between any of the breathwork groups and mindfulness meditation (data not shown).

Changes in physiological measures over time

Slope of respiratory rate (A), HRV (C), and RHR (D) over the course of the study in mindfulness meditation (n = 22) and all breathwork (n = 78) groups. Slope of respiratory rate in individual breathwork groups (cyclic sighing: n = 27, box breathing: n = 19, cyclic hyperventilation: n = 32) compared with mindfulness meditation (B). Each dot represents a participant (Mann-Whitney U test for comparison between two groups, Kruskal-Wallis test with Bonferroni-Holm correction for multi-group comparison, B). Upper and lower box edges represent 75th and 25th percentiles, respectively. The whiskers represent the largest and smallest data point that is less than 1.5 times the box length.

See also Figures S3 and S5 .

No changes in sleep were observed in any of the groups

We compared the changes in the sleep measures we received from WHOOP. Specifically, we looked at “hours of sleep”, “sleep efficiency,” and “sleep score.” There were no significant changes in these measures in either of the groups as well as between the groups ( Figures S3 A–S3C). To investigate daytime sleepiness, we compared the 8-item PROMIS sleep-related daytime disturbance score (T-score) at baseline and after the 28 days of exercise. There were no differences in the PROMIS sleep score in either of the groups, and there was no significant difference between the groups ( Figure S3 D).

We conducted a randomized controlled study to compare the psychophysiological effects of 5-min daily practice of three different breathing exercises and mindfulness meditation over 1 month. We assessed group differences in acute effects by using a linear mixed-effects modeling approach that took into account multiple measurements from each participant and the effect of adherence. We also looked at baseline and post-study measurements of sleep-related daytime disturbances, trait anxiety, and slopes of physiological measures throughout the study. We found differential effects of these exercises on both daily acute measures and physiological measures over the course of the study.

While all four groups showed significant daily improvement in positive affect and reduction in state anxiety and negative affect, there were significant differences between mindfulness meditation and breathwork in positive affect ( Figures 2 and ​ and3). 3 ). Our daily monitoring and mixed-effects modeling approach allowed us to measure impacts throughout the study and revealed that the positive affect benefits of the breathwork exercises increased with more practice over time ( Figure 2 ). Specifically, the cyclic sighing group showed more increase in positive affect toward the end of the study in a way that was significantly different than that for those randomized to mindfulness meditation, who had the least increase in positive affect ( Figure 3 ). Overall, breathwork practices, particularly cyclic sighing, were more effective than mindful meditation in increasing positive affect, supporting our hypothesis that intentional control over breath with specific breathing patterns produces more benefit to mood than passive attention to one’s breath, as in mindfulness meditation practice.

The breathwork group also showed significant physiological changes over time such that change in respiratory rate was significantly lower for the cyclic sighing group than mindfulness meditation group ( Figure 4 ). These physiological changes were associated with changes in positive affect over the course of the study. This result also supports our hypothesis that intentional control of breath is more effective in lowering sympathetic tone compared with mindfulness meditation practice.

Contemplative practices including meditation and other mind-body techniques have been shown to yield a wide range of benefits on cardiopulmonary health, immune and physical functions, and mental health. 38 While both meditative practice and controlled breathwork practices show similar benefits, our data reveal they seem to be largest in cyclic sighing, which differed from the other groups in two main ways: (1) extended exhalation and (2) the double inhale, which increases the depth of inhalation. Cyclic sighing produced the highest daily improvement in positive affect as well as the highest reduction of respiratory rate, both significantly different from mindfulness meditation. The physiological and psychological effects of cyclic sighing appear to last over time.

What are possible mechanisms through which voluntary breathing can influence physiology and mood differently than mindfulness meditation? One way is through modulating vagal function. The impact of different breathing techniques on heart physiology has been well established, and there is evidence that heart rate variability is a reflection of vagal function. 39 While we did not observe significant differences in heart rate variability across conditions in this study, it is reasonable to assume that the effect of deliberate breathing practices on brain function are, at least in part, mediated by vagus nerve pathways. Since heart and lung function are closely synchronized 40 and cardiac vagal control has been conceptualized as a marker of emotional control, 41 breath can directly influence the central autonomic network (CAN) and thus can explain the impact of breath on mood and sleep. In future studies, we plan to explore the specific brain regions activated by particular patterns of breathing and correlate those with vagal recordings and heart rate variability (HRV).

Furthermore, breath can also enhance interoceptive processes. Interoception, the sensing and processing of visceral stimuli through the ascending branch of the brain-body axis resulting in the conscious perception of bodily processes, plays a role in emotional experience, self-regulation, decision-making, and consciousness. The perception of our internal physical processes has the potential to amplify or modulate stress. 42 Early recognition of one’s own stress response, including increased heart rate, muscle tension, gastrointestinal discomfort, and sweating, can have the effect of transducing environmental discomfort into a physiological language that intensifies it. In other words, the more aware people are of their internal state, the more prone they can be to negatively interpreting subtle shifts in their physiology toward promoting sympathetic (higher-arousal) states. However, the same increase in interoceptive awareness can also provide a perceptual window into one’s ability to reduce physiological signs of stress, thereby providing a heightened sense of control and ability to regulate stress. 43 The literature on how mind-body practices influence interoception is complex. Mindfulness meditation interventions have been shown to be effective in improving interoceptive awareness in clinical populations that involve somatic symptoms such as post-traumatic stress disorder (PTSD) and substance use disorders (SUDs). 44 , 45 , 46 , 47 A meta-analysis of the effects of mindfulness training on body awareness has found a small, but significant, positive relationship between mindfulness and body awareness. 48 However, several studies have not found that interoception is improved in long-term meditators. 49 , 50 How voluntary breathwork practices influence interoceptive processes and how that compares with mindfulness meditation is not well studied, and we aim to explore this in future studies.

Controlled breathing can also directly influence the cortical structures regulating emotion and mood and arousal. Breathlessness and anticipation of breathlessness are both perceived as threatening and activate the limbic structures involved in emotion generation while inactivating cortical structures involved in emotional regulation such as the prefrontal cortex. 51 , 52 , 53 People with high anxiety and panic disorder have less tolerance for breathlessness and have heightened activity in the anterior insula, a region central to interoception of visceral signals and central to the salience network. 42 , 54 Thus, controlled breathing can potentially act in the opposite way and reduce anxiety by decreasing anterior insula activity. Breathing rhythms have been shown to directly modulate behavioral and physiological arousal in mice through the activity of the locus coeruleus, where experimentally induced slow breathing patterns have been associated with calm behaviors. 14 Thus, slowing down the breathing rhythm with sighs can signal higher-order brain structures associated with behavioral arousal and promote a sense of calm. Nasal breathing, such as in the cyclic sighing intervention, has also been shown to entrain high-frequency oscillations in the amygdala and hippocampus, two nodes involved in emotional processing. 6 More research into how breathing influences brain networks involved in emotional regulation and influence mood is needed in humans.

Finally, voluntary breathing exercises can also enhance the general sense of control over one’s internal state, contributing to the increase in positive affect observed. 55 This is different from mindfulness meditation, where the practitioner does not exert control over the breath rhythm. Diminished perceived sense of control has been linked to high anxiety and high anterior insula activity. 27 , 56 Respiration is at the cusp of this control mechanism because it is a necessary physiological system that functions without conscious thought but can be easily controlled with a modicum of attention. Indeed, breathing itself is a mechanism by which changes in heart rate occur and may be controlled to adjust the state of mind (Cicero et al., 37 our data in the present study). Thus, managed breathing is a tool to enhance the domain of psychophysiological regulation.

Since interoceptive awareness, however, is ambiguous and plays a role in some mental disorders with a physical component such as panic disorders, somatoform disorders, eating disorders, and PTSD, 57 being able to take conscious control over mechanics of breathing might be beneficial in such populations. Selecting patient populations with interoceptive psychopathology to help modify the interface between autonomic systems and the CNS through breath has beneficial potential in such populations. Including interoceptive measures in future studies can furthermore help discern what populations can most benefit from different breathing techniques. 48

Our study monitored subjects daily and collected daily physiological data remotely, a capability that was forced by the COVID restrictions but was enabled by the wearable technology that the WHOOP strap offered. The use of wearables enabled us to assess the changes longitudinally as opposed to just in two time points before and after the study and revealed differences in groups over time that would not be otherwise possible. 58 It also allowed us to include a geographically diverse participant pool. A limitation of this remote study was having less control over some variables that may influence the results such as knowing how exactly the subjects practiced the exercises or controlling exactly how long they practiced. We advise future remote studies to take such variables into consideration. Overall, the study showed that remote administration of interventions is effective and that physiological monitoring is possible. Our results also support the importance of the discipline of daily practice to see substantial effects. Altogether, our study paves the way for deeper in-lab and remote mechanistic explorations to understand the differential impacts that distinct breathing techniques can have on mood and respiratory function.

Limitations of the study

This study was originally intended as an exploratory study in preparation for a larger clinical trial and thus was not pre-registered as a clinical trial. We wanted to test out the feasibility of delivering interventions and conducting data collection 100% remotely during the COVID pandemic. We also were unsure about whether or not we would obtain adequate adherence to the protocol as the pandemic unfolded. At the same time, given the widespread stress the pandemic was causing, we felt it important to proceed with what could be characterized as a phase 1/2 toxicity/initial efficacy trial were the intervention a drug or device. As it turned out, we obtained interesting preliminary results demonstrating positive effects of breathwork, and adherence itself influenced the outcome. We registered the trial retrospectively (ClinicalTrials.gov: {"type":"clinical-trial","attrs":{"text":"NCT05304000","term_id":"NCT05304000"}} NCT05304000 ) and are now planning a larger confirmatory trial that will be pre-registered.

The remote nature of the study limited the monitoring of how closely participants followed the instructions on a daily basis. In addition, we had to rely on the completion of daily surveys to assess adherence. Adherence can be better monitored and enforced in future studies by implementing automatic time stamping when participants start and end their exercise. In addition, the findings of this study are limited to 4 weeks with no additional follow up. Future studies should investigate how long lasting the effects are and what the minimum effective daily dose and minimum amount of adherence are, particularly with respect to the physiological outcomes. Finally, sample size in each group was relatively small, limiting the statistical power to compare individual breathwork groups with each other. However, the study was sufficiently powered to compare the combined effects of breathwork practice to the mindfulness meditation practice.

STAR★Methods

Key resources table, resource availability, lead contact.

Further information and requests for resources and reagents should be directed to and will be fulfilled by the lead contact, Andrew D. Huberman ( [email protected] ).

Materials availability

This study did not generate new unique reagents.

Experimental model and subject details

Participants.

The 108 participants included females and males 18 and older (refer to Table S1 for details on demographics) who could read and understand English well enough to consent, complete measures and follow instructions. For health and safety reasons, we excluded those with self-reported moderate to severe psychiatric or medical conditions that could be exacerbated by study participation, such as heart disease, glaucoma, history of seizures, pregnancy, psychosis, suicidality, bipolar disorder, or substance use disorders. Excluded also were those with vision or hearing impairment severe enough to interfere with study participation, such as reading study material and watching and listening to the instruction videos for the interventions.

Participant recruitment began on June 2, 2020, during the COVID-19 pandemic, and data collection ended on September 17, 2020. All recruitment and study participation were conducted remotely. Most of the participants were recruited from an undergraduate psychology class at Stanford University, and a few by word of mouth. See Figure S1 for a detailed consort diagram. This study was approved by the Stanford Institutional Review Board and conformed to HIPAA regulations.All procedures have been approved under the Stanford IRB protocol #41398. The trial was retrospectively registered to clinicaltrials.gov .

Method details

This study employed a repeated-measures, randomized controlled design. All phases of the study were conducted online (screening, consenting/enrollment, interventions, and assessments). Data were collected using the secure Stanford REDCap platform ( http://redcap.stanford.edu ), developed and operated by the Stanford Medicine Research IT team. Members of the research team were available through e-mail and telephone.

A WHOOP strap (WHOOP Inc., Boston, MA) was mailed to eligible study participants after e-signing of the study consent form. This device uses a wrist-worn LED photoplethysmograph to monitor HR, and from which HRV can be calculated, and a tri-axial accelerometer to monitor movement, data from which can be used to impute sleep vs. wake. Participants had sufficient time between receiving the device and the start of data collection to learn how to operate the strap. In addition to the continuous acquisition of WHOOP data, we also assessed participants’ anxiety and mood daily prior to and immediately after the exercises via Redcap surveys. Participants had access to their own WHOOP data through the commercial app; the study team had access to daily data and raw data for all participants, downloaded directly from WHOOP. Participants logged in to the WHOOP mobile application using de-identified e-mail addresses provided by the study team. The identities of the participants were thus masked from WHOOP unless participants voluntarily used their personal emails.

From the 108 subjects enrolled, 24 were randomized into the Mindfulness Meditation control condition and 84 were randomized to the treatment conditions (30 Cyclic Sighing, 21 Box Breathing, 33 Cyclic Hyperventilation with Retention). The initial randomization consisted of a permuted block randomization design with a block size of eight. Therefore, group sizes should have been balanced for every eight participants. During the course of mailing the WHOOP straps to the participants, it became evident that there were some participants who were from the same household. To assure fidelity to treatment type, eight households were randomized to the same condition, seven households with two participants and one household with three. This accounts for the imbalanced group sizes.

Both prior to and after the 28-day intervention, participants completed two brief questionnaires to assess the impact of the intervention on the daytime sequelae of sleep and anxiety: PROMIS Sleep Related Impairment – Short Form 8a 59 and the State-Trait Anxiety Questionnaire. 60 Participants also completed a debriefing questionnaire at the end of the study. In lieu of direct remuneration, participants who completed study participation were gifted the WHOOP Strap (approximately $350 in value) and a waived 6-month (included study participation time) subscription fee ($180 in value).

During the 28-day intervention period, participants did their assigned 5-min exercise and completed two questionnaires before and after, the State Anxiety Inventory 60 and the Positive and Negative Affect Schedule (PANAS). 61 Participants received invitations to instructional videos (pre-recorded by Andrew D. Huberman) on the breathing exercises 3–5 days prior to the start of the study as well as daily text messages that reminded them to complete their exercises and pre-and-post-practice assessments. They were asked to complete the exercises only once a day. See Supplementary text for detailed instructions for each protocol.

Description of breathing protocols

• A) Mindful Meditation

Participants were informed they should sit down in a chair or, if they preferred, to lie down, and then to set a timer for 5 min. Then they were told to close their eyes and to start breathing while focusing their mental attention on their forehead region between their two eyes. They were told that if their focus drifted from that location to re-recenter their attention by focusing back first on their breath and then on the forehead region between their eyes. They were told that as thoughts arise, to recognize that as normal, refocus their attention back to their forehead region and to continue the practice until time has elapsed.

• B) Cyclic Sighing

Participants were informed they should sit down in a chair or, if they prefer, to lie down, and to set a timer for 5 min. Then they were told to inhale slowly, and that once their lungs were expanded, to inhale again once more to maximally fill their lungs -- even if the second inhale was shorter in duration and smaller in volume than the first, and then to slowly and fully exhale all their breath. They were told to repeat this pattern of breathing for 5 min. They were also informed that ideally, both inhales would be performed via their nose and the exhale would be performed via their mouth, but that if they preferred, they were welcome to do the breathing entirely through their nose. They were also informed that it is normal for the second inhale to be briefer than the first.

Then they were told to return to breathing normally.

• C) Box Breathing

Participants were informed they should sit down in a chair or, if they prefer, to lie down, and to get a timer with a seconds counter that they could watch.

Then they were told to take the “CO2 tolerance test” as follows.

• 1) Take 4 breaths. An inhale followed an exhale = 1 breath. Ideally these are all done via the nose.
• 2) Then take a maximally deep breath and once your lungs are full, exhale as slowly as possible through your nose or mouth.
• 3) Time how long it takes (in sec) to empty your lungs; this will be your C0 2 discard duration.
• 4) Do not hold your breath with lungs empty. Once your lungs are empty simply record your ‘discard duration.
• 5) Use your discard duration to determine how long your inhales, exhales, and breath holds should be for the box breathing protocol using this table:

· 0–20 s C0 2 discard time = your inhales, exhales, and breath holds should be 3 - 4s.

· 25–45 s C0 2 discard time = your inhales, exhales, and breath holds should be 5 - 6s.

50 - 75 + sec C0 2 discard time = your inhales, exhales, and breath holds should be 8–10 s.

Participants were informed they should sit down in a chair or, if they prefer, to lie down, and to set a timer for 5 min. They were told to then inhale (for the duration determined by the C0 2 discard rate lookup table), then to hold their breath for the equivalent duration, then to exhale for the same duration and then to hold their breath for again, the same duration (e.g. inhale 4 s, hold 4 s, exhale 4 s, hold 4 s) and to repeat this pattern for the entire 5 min. They were told that if at any point they had to strain to reach these times, they should simply reduce the duration of inhales, exhales, and breath holds. We asked participants to perform all breathing through their nose, if possible, but that if they felt the need to switch to breathing through their mouth, to do so.

• D) Cyclic Hyperventilation with Retention

Participants were informed they should sit down in a chair or, if they prefer, to lie down, and to set a timer for 5 min. Then they were told to inhale deeply (ideally through their nose but if that is not possible, to inhale through their mouth) and then exhale by passively letting the air "fall out from the mouth". We informed them that for sake of this protocol, that pattern of a deep inhale through the nose and passively letting the air "fall out from the mouth” = 1 breath.

Then they were instructed to perform 30 breaths (in and out) in this manner, and after those 30 breaths, to exhale all their air via their mouth and to calmly wait with lungs empty for 15 s.

We called this cycle of 30 breaths in and out, followed by a lung-emptying exhale and 15 s breath retention (hold) with lungs empty, “Round 1”.

Then they were instructed to perform this for a “Round 2” as well:

30 breaths in-and-out = 1 breath (deep inhale through nose, then “passively exhale” - let air fall out from the mouth".

Then after 30 breaths, to exhale all their air and hold to calmly wait with lungs empty for 15 s before repeating.

Then they were instructed to perform this for a “Round 3”:

30 breaths in and out = 1 breath (deep inhale through nose, let air "fall out from the mouth").

Then after 30 breaths, to exhale all their air and hold to calmly wait with lungs empty for 15 s.

Psychological measures

PROMIS Short Form v1.0 – Sleep-Related Impairment 8a form: This measure contains eight items asking about the raters' self-reported perceptions on sleep-related daytime impairments during the past seven days, with a Likert-type scale (1–5 = Not at all to Very much, 59 ). Data were scored using a T-score transformation according to standard instructions ( https://www.healthmeasures.net/promis-scoring-manuals ).

Positive and Negative Affect Schedule (PANAS): This is an adjective list of emotions with a Likert-type scale (1–5 = slightly to extremely) and instructions to rate feelings in the moment. 61 The positive and negative affect measures have been shown to be highly internally consistent, largely uncorrelated, and stable at appropriate levels over a two-month time period. 62 Normative data and factorial and external evidence of convergent and discriminant validity for the scales are robust. Sums of the positive and negative items were used as scores for current ‘positive’ and ‘negative’ affect.

State Trait Anxiety Inventory (STAI): The STAI is composed of two parts, each with 20 items, that measure state and trait anxiety. The state anxiety form contains questions about how the rater feels at the moment, such as “I feel calm”, “I feel upset”, with a Likert-type scale (1–5 = Not at all to Very much so). The trait anxiety form contains questions about how the rater generally feels, such as “I feel secure”, “I feel inadequate”, with a Likert-type scale (1–5 = Almost never to Almost always). 60 The sums of these two parts were used as scores for ‘state’ and ‘trait’ anxiety.

Debrief Survey: The de novo survey is composed of 11 items regarding participants' perspectives on the quality of the interventions and their experience with the interventions. For four of the items, participants rate their response on a Likert scale and seven of the items are open-ended measures.

Physiological measures

Daily resting heart rate (RHR), respiratory rate (RR), and Heart Rate Variability (HRV, root-mean-square of successive differences between normal heartbeats, RMSSD) summaries were obtained from WHOOP. WHOOP calculates resting heart rate and heart rate variability during deep sleep through their proprietary algorithms ( https://support.whoop.com/hc/en-us/articles/360019622593-What-is-Heart-Rate-Variability-HRV- ). These values were used to calculate the physiological effects of the exercises over the course of 28 days. Changes in these metrics were calculated as the slope of the linear regression line fit to the daily values obtained throughout the study. Differences between groups were calculated with non-parametric Mann-Whitney U test (for two group comparison) and Kruskal-Wallis test with Bonfferini-Holm correction (for multi-group comparisons).

Nighttime sleep

Daily “Hours of Sleep”, “Sleep Efficiency” and “Sleep Score” measures were obtained from WHOOP and were analyzed the same way as the daily HRV, RHR and RR measures.

Quantification and statistical analysis

Daily subjective measures (stai and panas).

Changes in STAI state anxiety and PANAS positive and negative affect scores were calculated by subtracting the pre-condition score from the post-condition score daily for each participant. Participants were assumed to have completed the breathing protocol if they had filled out the pre- and post-measures for a particular day. Average daily change scores were calculated by averaging the daily changes in state anxiety and PANAS scores of each participant over the number of days they followed the protocol, then averaging this across all subjects within a group. For each group, average daily post-scores per person were compared to average daily pre-scores with a paired Wilcoxon test to assess if there was a significant change between pre- and post-conditions. A mixed-effects modeling approach was used to compare changes across groups ( Figure 2 ). Daily change between pre and post protocol for each subject was used as the main unit for modeling. All variables were centered by subtracting the mean before feeding into the model. The cumulative day variable was centered at day 28. Data processing was performed in R and linear mixed-effects modeling was conducted using the “fitlme” function in MATLAB.

Baseline and follow-up measures (STAI trait anxiety, PROMIS sleep-related daytime disturbance)

Changes in both trait anxiety and sleep-related daytime disturbance were calculated by subtracting the pre-score from the post-score and compared across groups with unpaired Wilcoxon test. Pre-scores were also compared to post-scores within each group with a paired Wilcoxon test.

Additional resources

This trial was retrospectively registered ( {"type":"clinical-trial","attrs":{"text":"NCT05304000","term_id":"NCT05304000"}} NCT05304000 ).

Acknowledgments

This work was supported by generous support from Victor and Winnie Koo and Tianren Culture and a Stanford School of Medicine Discovery Innovation Award (A.D.H.). We also thank WHOOP for generously donating the wrist straps used in the study. WHOOP was not involved in the design or analysis of this study.

Author contributions

M.Y.B., J.M.Z., D.S., and A.D.H. designed research; M.Y.B., E.N., B.N., and G.H. performed research; M.Y.B., L.W., E.N., B.N., B.J., and M.M.K. analyzed data; and M.Y.B., M.M.K., L.W., J.M.Z., D.S., and A.D.H. wrote the paper.

Declaration of interests

A.D.H. became an advisor to WHOOP in June of 2022.

Inclusion and diversity

We support inclusive, diverse, and equitable conduct of research.

Published: January 10, 2023

Supplemental information can be found online at https://doi.org/10.1016/j.xcrm.2022.100895 .

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One Thing Most Countries Have in Common: Unsafe Air

New research found that fewer than 10 percent of countries and territories met World Health Organization guidelines for particulate matter pollution last year.

By Delger Erdenesanaa

Only 10 countries and territories out of 134 achieved the World Health Organization’s standards for a pervasive form of air pollution last year, according to air quality data compiled by IQAir , a Swiss company.

The pollution studied is called fine particulate matter, or PM2.5, because it refers to solid particles less than 2.5 micrometers in size: small enough to enter the bloodstream. PM2.5 is the deadliest form of air pollution, leading to millions of premature deaths each year .

“Air pollution and climate change both have the same culprit, which is fossil fuels,” said Glory Dolphin Hammes, the CEO of IQAir’s North American division.

The World Health Organization sets a guideline that people shouldn’t breathe more than 5 micrograms of fine particulate matter per cubic meter of air, on average, throughout a year. The U.S. Environmental Protection Agency recently proposed tightening its standard from 12 to 9 micrograms per cubic meter.

The few oases of clean air that meet World Health Organization guidelines are mostly islands, as well as Australia and the northern European countries of Finland and Estonia. Of the non-achievers, where the vast majority of the human population lives, the countries with the worst air quality were mostly in Asia and Africa.

Where some of the dirtiest air is found

The four most polluted countries in IQAir’s ranking for 2023 — Bangladesh, Pakistan, India and Tajikistan — are in South and Central Asia.

Air quality sensors in almost a third of the region’s cities reported concentrations of fine particulate matter that were more than 10 times the WHO guideline. This was a proportion “vastly exceeding any other region,” the report’s authors wrote.

The researchers pointed to vehicle traffic, coal and industrial emissions, particularly from brick kilns, as major sources of the region’s pollution. Farmers seasonally burning their crop waste contribute to the problem, as do households burning wood and dung for heat and cooking.

China reversed recent gains

One notable change in 2023 was a 6.3 percent increase in China’s air pollution compared with 2022, after at least five years of improvement. Beijing experienced a 14 percent increase in PM2.5 pollution last year.

The national government announced a “war against pollution” in 2014 and had been making progress ever since. But the sharpest decline in China’s PM2.5 pollution happened in 2020, when the coronavirus pandemic forced much of the country’s economic activity to slow or shut down. Ms. Dolphin Hammes attributed last year’s uptick to a reopening economy.

And challenges remain: Eleven cities in China reported air pollution levels last year that exceeded the WHO guidelines by 10 times or more. The worst was Hotan, Xinjiang.

Significant gaps in the data

IQAir researchers analyze data from more than 30,000 air quality monitoring stations and sensors across 134 countries, territories and disputed regions. Some of these monitoring stations are run by government agencies, while others are overseen by nonprofit organizations, schools, private companies and citizen scientists.

There are large gaps in ground-level air quality monitoring in Africa and the Middle East, including in regions where satellite data show some of the highest levels of air pollution on Earth.

As IQAir works to add data from more cities and countries in future years, “the worst might be yet to come in terms of what we’re measuring,” Ms. Dolphin Hammes said.

Wildfire smoke: a growing problem

Although North America is one of the cleaner regions in the world, in 2023 wildfires burned 4 percent of Canada’s forests, an area about half the size of Germany, and significantly impaired air quality.

Usually, North America’s list of most polluted cities is dominated by the United States. But last year, the top 13 spots all went to Canadian cities, many of them in Alberta.

In the United States, cities in the Upper Midwest and the Mid-Atlantic states also got significant amounts of PM2.5 pollution from wildfire smoke that drifted across the border.

Risks of short-term exposure

It’s not just chronic exposure to air pollution that harms people’s health.

For vulnerable people like the very young and old, or those with underlying illnesses, breathing in large amounts of fine particulate pollution for just a few hours or days can sometimes be deadly. About 1 million premature deaths per year can be attributed to short-term PM2.5 exposure, according to a recent global study published in The Lancet Planetary Health.

The problem is worst in East and South Asia, as well as in West Africa.

Without accounting for short-term exposures, “we might be underestimating the mortality burden from air pollution,” said Yuming Guo, a professor at Monash University in Melbourne, Australia, and one of the study’s authors.

U.S. disparities widen

Within individual countries, air pollution and its health effects aren’t evenly distributed.

Air quality in the United States has generally been improving since the Clean Air Act of the 1970s. Last decade, premature deaths from PM2.5 exposure declined to about 49,400 in 2019, down from about 69,000 in 2010.

But progress has happened faster in some communities than in others. Racial and ethnic disparities in air pollution deaths have grown in recent years, according to a national study published this month .

The census tracts in the United States with the fewest white residents have about 32 percent higher rates of PM2.5-related deaths, compared with those with the most white residents. This disparity in deaths per capita has increased by 16 percent between 2010 and 2019.

The study examined race and ethnicity separately, and found the disparity between the census tracts with the most and least Hispanic residents grew even more, by 40 percent.

In IQAir’s rankings, the United States is doing much better than most other countries. But studies that dig deeper show air quality is still an issue, said Gaige Kerr, a research scientist at George Washington University and the lead author of the disparities paper published in the journal Environmental Health Perspectives. “There’s still a lot of work to do,” he said.

Dr. Kerr’s research showed that mortality rates were highest on the Gulf Coast and in the Ohio River Valley, in areas dominated by petrochemical and manufacturing industries. He also noted that researchers have seen a slight uptick in rates of PM2.5-related deaths starting around 2016, particularly in the Western states, likely because of increasing wildfires.

Delger Erdenesanaa is a reporter covering climate and the environment and a member of the 2023-24 Times Fellowship class, a program for journalists early in their careers. More about Delger Erdenesanaa

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EPA Research at NACCHO Preparedness Summit | 2024

Come visit us at the EPA Booth (#1205) to meet EPA researchers and see live demonstrations of EPA tools!

Tag us @EPAResearch and #Prep24

EPA is participating in the 2024 National Association of County and City Health Officials (NACCHO) Preparedness Summit from March 25-28 in Cleveland, Ohio. EPA's latest research in aerosol research, artificial intelligence, and community engagement to support disaster preparedness will be featured at a demonstration session, town hall, and EPA's booth.

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Equitable Resilience Builder: An Inclusive Approach to Addressing Disasters and Climate Change

Live session demonstration,  room 5 , march 25 at 3:30 - 5:00 pm et.

Presenters: Ian Reilly, Raven Nee, and Maureen Shacklette, EPA Office of Research and Development

The urgent need to build resilience in low-income and underrepresented communities with hazardous and polluting sites stems from the threat of cascading and compounding disasters. The Equitable Resilience Builder (ERB) is a new tool designed for situations with limited capacity and resources. ERB builds and strengthens partnerships as it guides users through resilience planning. ERB is a downloadable application that was developed using human-centered design. Using collaborative workshops, users assess hazards, vulnerability, and resilience, and identify actions to strengthen community resilience. Activities include diagramming community connections, storytelling, participatory mapping, and indicator card sorting. This session will introduce the tool using two activities: indicator card sorting to assess resilience, and storytelling to build community connections, trust, and shared local knowledge. Participants will become familiar with ERB and how it advances environmental and health equity and social justice.

From filters to algorithms: The breath and bytes of Environmental Protection Agency (EPA) research

Live town hall event, march 27 at 1:30-3:00 pm et.

Presenters: Katherine Ratliff and Timothy Boe, EPA Office of Research and Development

Join EPA researchers as they discuss public health preparedness, from simple tools to advanced systems. This session will discuss how an easy-to-make low cost air cleaner can be used to effectively reduce infectious aerosols and particulate matter in classrooms and other indoor spaces. Participants will have an opportunity to build an air cleaner while researchers showcase how the simple design is already being used in schools. The discussion will then turn to applications of artificial intelligence in public health and how it can forge new paths in preparedness for practitioners. The town hall encourages participation from attendees.  

Timothy Boe  is a Geographer with EPA's Homeland Security Research Program. Mr. Boe's work primarily focuses on response and waste management issues following CBRN incidents. He has also been developing computer-based decision support tools to aid decision makers in responding to wide-area contamination incidents. Before joining EPA, Timothy worked as an Oak Ridge Institute for Science and Education (ORISE) fellow where he conducted research on wide area CBRN remediation. Timothy has an M.S. and a B.S. in applied science from Arkansas Tech University (Russellville).

Raven Nee  is an ORISE Community Resilience and Equity Social Science fellow in US EPA's Office of Research and Development, Center for Public Health and Environmental Assessment. Her background is in environmental studies and sustainable urban planning and she is especially interested in intersectional equity and climate resilience.

Dr. Katherine Ratliff   is a physical scientist and principal investigator in the Center for Environmental Solutions and Emergency Response at the U.S. Environmental Protection Agency's Office of Research and Development. She uses numerical models, labs, and field-scale studies to develop and evaluate tools for remediating environmental contaminants, including leading EPA's research to evaluate the effectiveness of different air cleaning and treatment technologies against airborne pathogens. Dr. Ratliff received her B.A. in Earth and Environmental Sciences from Vanderbilt University and a Ph.D. in Earth and Ocean Sciences from Duke University.

Ian Reilly  is an Oak Ridge Institute for Science and Education (ORISE) Fellow with the U.S. Environmental Protection Agency in the Office of Research and Development, where his research involves studying and responding to issues at the intersection of natural resource planning, climate change, and equitable community resilience. He is a contributor on multiple noteworthy projects in the Integrated Climate Sciences Division, including the Equitable Resilience Builder (ERB) and the Adaptation Organon.

Ian earned his Master of Public Health in 2022 from Yale School of Public Health, studying health policy and the impacts of climate change on public health. During this time Ian contributed as the lead author of  Centering Equity in Climate Change Resilience Planning: Guidance for Connecticut Municipalities , an equity-focused guideline for community-level assessment of climate change vulnerability and solutions development published by the Yale Center for Environmental Justice in collaboration with Yale Center for Climate Change and Health.

Ian is a motivated public health professional interested in researching integration and implementation of social science methodologies in natural resource management and community planning, particularly in the context of underserved communities most vulnerable to climate change threats.

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