THE CENTER WITHIN · EVIDENCE LIBRARY

Slow, structured breathing and HRV biofeedback

Breathwork

B – Moderate10 verified peer-reviewed articles

WHAT THE RESEARCH SHOWS

Breathing is the one part of the autonomic nervous system we can steer on purpose. Slowing the breath to roughly six breaths per minute, lengthening the exhale, or training with heart rate variability (HRV) biofeedback are the most-studied ways to shift toward parasympathetic ("rest-and-digest") activity. The strongest evidence is physiological. A 2022 meta-analysis of 223 studies found that voluntary slow breathing increases vagally mediated HRV during practice, right after a session, and after multi-week programs. For psychological outcomes, a 2023 meta-analysis of randomized trials found breathwork was associated with lower stress, anxiety and depressive symptoms than control conditions. HRV biofeedback meta-analyses report moderate-to-large reductions in stress and anxiety. Blood pressure, heart rate and cardiovascular responses to stress are promising longevity-related surrogate markers, but those trials are still small.

the studies,

READ THE EVIDENCE

10 of 10 studies

A – StrongSlow breathing increases vagal HRV (meta-analysis of 223 studies)Systematic review & meta-analysis · Parasympathetic

IN PLAIN LANGUAGE

Across more than 200 studies, slowing the breath consistently raised heart rate variability, a measurable sign of parasympathetic (calming) nervous system activity. The authors describe slow breathing as a low-tech, low-cost practice with few expected side effects.

Study type: Systematic review & meta-analysis
Who was studied: 223 studies (172 during-session, 16 immediately after, 49 multi-session)
Outcome area: Parasympathetic
Key finding: Voluntary slow breathing increased vagally mediated HRV during practice, immediately after a single session, and after multi-session interventions.
Evidence grade: A – Strong
Limitations: Many included studies were small; breathing protocols varied widely.
Citation: Laborde S, Allen MS, Borges U, et al. Effects of voluntary slow breathing on heart rate and heart rate variability: A systematic review and a meta-analysis. Neurosci Biobehav Rev. 2022;138:104711.

PubMed 35623448 DOI 10.1016/j.neubiorev.2022.104711

B – ModerateBreathwork lowers stress, anxiety and depressive symptoms (meta-analysis of RCTs)Meta-analysis of RCTs · Tension / stress

IN PLAIN LANGUAGE

Pooling randomized trials, people who practiced breathwork reported less stress, anxiety and low mood than people in comparison groups. The effects were small to moderate, and the authors call for more high-quality trials.

Study type: Meta-analysis of RCTs
Who was studied: 12 RCTs, 785 adults (primary outcome); 20 RCTs for anxiety, 18 for depression
Outcome area: Tension / stress
Key finding: Breathwork was associated with lower self-reported stress (g = −0.35), anxiety (g = −0.32) and depressive symptoms (g = −0.40) than non-breathwork controls.
Evidence grade: B – Moderate
Limitations: Most trials at moderate risk of bias; moderate heterogeneity. The authors caution against hype.
Citation: Fincham GW, Strauss C, Montero-Marin J, Cavanagh K. Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials. Sci Rep. 2023;13(1):432.

PubMed 36624160 DOI 10.1038/s41598-022-27247-y

B – ModerateFive minutes of daily cyclic sighing improved mood (Stanford RCT)Randomized controlled trial (remote, 1 month) · Tension / parasympathetic

IN PLAIN LANGUAGE

In a one-month randomized study, a 5-minute daily "cyclic sighing" practice (two inhales, then a long, slow exhale) improved mood and lowered breathing rate more than the same time spent in mindfulness meditation.

Study type: Randomized controlled trial (remote, 1 month)
Who was studied: Healthy adults; 3 breathwork arms vs mindfulness meditation
Outcome area: Tension / parasympathetic
Key finding: Breathwork, especially exhale-focused cyclic sighing, produced greater mood improvement and larger reductions in resting respiratory rate than mindfulness meditation (p < 0.05).
Evidence grade: B – Moderate
Limitations: Remote, self-guided design; one-month duration; healthy volunteers.
Citation: Balban MY, Neri E, Kogon MM, et al. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Rep Med. 2023;4(1):100895.

PubMed 36630953 DOI 10.1016/j.xcrm.2022.100895

B – ModerateHRV biofeedback reduces stress and anxiety (meta-analysis)Meta-analysis · Tension / stress

IN PLAIN LANGUAGE

HRV biofeedback teaches you to breathe at a pace that maximizes heart rate variability, often using a wearable. Across 24 studies, this training was linked to large reductions in stress and anxiety.

Study type: Meta-analysis
Who was studied: 24 studies, 484 participants
Outcome area: Tension / stress
Key finding: HRV biofeedback was associated with a large reduction in self-reported stress and anxiety (between-group Hedges g = 0.83).
Evidence grade: B – Moderate
Limitations: Small total sample; authors call for more well-controlled studies.
Citation: Goessl VC, Curtiss JE, Hofmann SG. The effect of heart rate variability biofeedback training on stress and anxiety: a meta-analysis. Psychol Med. 2017;47(15):2578-2586.

PubMed 28478782 DOI 10.1017/S0033291717001003

B – ModerateHRV biofeedback improves emotional and physical health (meta-analysis of 58 RCTs)Systematic review & meta-analysis · Tension / stress

IN PLAIN LANGUAGE

Across 58 randomized studies, HRV biofeedback improved a range of emotional and physical outcomes, with the clearest benefits for anxiety, depression and anger. The authors see it as a useful complementary approach.

Study type: Systematic review & meta-analysis
Who was studied: 58 randomized controlled studies
Outcome area: Tension / stress
Key finding: Small-to-moderate overall effect favoring HRV biofeedback; largest effects for anxiety, depression and anger; smallest for PTSD, sleep and quality of life.
Evidence grade: B – Moderate
Limitations: Few studies per condition. An erratum was published (PMID 34623527); findings unchanged.
Citation: Lehrer P, Kaur K, Sharma A, et al. Heart Rate Variability Biofeedback Improves Emotional and Physical Health and Performance: A Systematic Review and Meta Analysis. Appl Psychophysiol Biofeedback. 2020;45(3):109-129.

PubMed 32385728 DOI 10.1007/s10484-020-09466-z

C – EmergingDiaphragmatic breathing lowers physiological and psychological stress (systematic review)Systematic review · Tension / parasympathetic

IN PLAIN LANGUAGE

Belly (diaphragmatic) breathing was linked to lower stress on both questionnaires and body measures such as cortisol and blood pressure, although only three studies were available.

Study type: Systematic review
Who was studied: 3 studies (1 RCT, 2 quasi-experimental)
Outcome area: Tension / parasympathetic
Key finding: All three studies found diaphragmatic breathing reduced stress, including improvements in salivary cortisol, respiratory rate and blood pressure in individual studies.
Evidence grade: C – Emerging
Limitations: Only 3 studies; pooling not possible; small samples.
Citation: Hopper SI, Murray SL, Ferrara LR, Singleton JK. Effectiveness of diaphragmatic breathing for reducing physiological and psychological stress in adults: a quantitative systematic review. JBI Database System Rev Implement Rep. 2019;17(9):1855-1876.

PubMed 31436595 DOI 10.11124/JBISRIR-2017-003848

B – ModerateDiaphragmatic breathing: 48 RCTs reviewedSystematic review of RCTs · Tension / stress

IN PLAIN LANGUAGE

The most up-to-date review of belly-breathing trials found consistent benefits for anxiety and several physical conditions, and no serious side effects. The authors note that many studies were not well designed.

Study type: Systematic review of RCTs
Who was studied: 48 RCTs in adults
Outcome area: Tension / stress
Key finding: Consistent benefits were found for anxiety, GERD, post-COVID-19 syndrome and gestational diabetes, with acute cardiovascular benefits in healthy adults. No serious adverse events were noted.
Evidence grade: B – Moderate
Limitations: Very few outcomes at low risk of bias; protocols highly heterogeneous.
Citation: Kwon CY, Won J, Lee B. The health effects of diaphragmatic breathing: A systematic review. Complement Ther Med. 2026;96:103317.

PubMed 41482169 DOI 10.1016/j.ctim.2025.103317

B – Moderate12 weeks of slow breathing reduced anxiety; exhale ratio did not matterRandomized, single-blinded trial (12 weeks) · Tension / stress

IN PLAIN LANGUAGE

Twelve weeks of slow breathing lowered anxiety. Whether the exhale was longer than the inhale made no significant difference. This is a helpful reminder that consistency may matter more than the exact technique.

Study type: Randomized, single-blinded trial (12 weeks)
Who was studied: 100 healthy adults
Outcome area: Tension / stress
Key finding: Regular slow breathing significantly reduced PROMIS anxiety, but not HRV. Extending the exhale did not produce a statistically significant extra benefit.
Evidence grade: B – Moderate
Limitations: Healthy volunteers; physiological change not significant. Included here as a balancing finding.
Citation: Birdee G, Nelson K, Wallston K, et al. Slow breathing for reducing stress: The effect of extending exhale. Complement Ther Med. 2023;73:102937.

PubMed 36871835 DOI 10.1016/j.ctim.2023.102937

C – EmergingSlow breathing + muscle relaxation lowered blood pressure in hypertensionRandomized controlled trial (4 arms, 4 weeks) · Longevity marker (blood pressure)

IN PLAIN LANGUAGE

In people with high blood pressure, four weeks of slow breathing paired with progressive muscle relaxation lowered blood pressure, heart rate and perceived stress.

Study type: Randomized controlled trial (4 arms, 4 weeks)
Who was studied: 64 adults with essential hypertension
Outcome area: Longevity marker (blood pressure)
Key finding: Combined slow breathing and progressive muscle relaxation reduced heart rate, respiratory rate, blood pressure and perceived stress compared with either technique alone or no treatment.
Evidence grade: C – Emerging
Limitations: Small groups (16 each); short duration; unblinded.
Citation: Pathan FKM, Pandian JS, Shaikh AI, et al. Effect of slow breathing exercise and progressive muscle relaxation technique in the individual with essential hypertension: A randomized controlled trial. Medicine (Baltimore). 2023;102(47):e35792.

PubMed 38013368 DOI 10.1097/MD.0000000000035792

C – EmergingHRV biofeedback improved heart blood flow during mental stress (JAMA Netw Open pilot)Pilot randomized clinical trial · Longevity marker (cardiovascular)

IN PLAIN LANGUAGE

In a small pilot study of people with heart disease, six weeks of guided breathing biofeedback improved blood flow to the heart during a mental stress test, suggesting a possible heart- protective effect worth studying further.

Study type: Pilot randomized clinical trial
Who was studied: 21 adults with coronary artery disease
Outcome area: Longevity marker (cardiovascular)
Key finding: Six weeks of HRV biofeedback increased myocardial flow reserve during mental stress compared with usual care (between-group difference 0.10, P = .03).
Evidence grade: C – Emerging
Limitations: Very small pilot; single center; needs larger trials.
Citation: Shah AJ, Raggi P, She H, et al. Heart Rate Variability Biofeedback and Mental Stress Myocardial Flow Reserve: A Randomized Clinical Trial. JAMA Netw Open. 2025;8(10):e2538416.

PubMed 41118163 DOI 10.1001/jamanetworkopen.2025.38416

EDUCATIONAL DISCLAIMER

This library is for educational purposes and is not medical advice. Individual results vary. Consult a qualified provider before starting any new therapy. Citations were verified against PubMed on September 25, 2026.

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