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Slow-paced breathing

Deliberately slowing the breath to a steady fixed pace, usually guided by a pacer, timer or count instead of breathing as usual.

At a glance

  • Evidence: Three independent syntheses of randomized trials agree that regular slow breathing lowers blood pressure modestly.Blood pressure (systolic and diastolic) · Moderate certainty · Randomized intervention
  • What’s uncertain: Trials are small and heterogeneous, and attention or expectations may contribute; long-term clinical benefits are not established.
  • First step: Sit comfortably and breathe slowly without straining; about six breaths per minute is an editorial starting point, not a proven optimum.
  • Before you try it: Do not replace prescribed blood-pressure medication with slow breathing. All precautions
Read the full takeaway

Blood pressure and symptoms

Meta-analyses of randomized trials support a modest reduction in blood pressure from regular slow breathing, of roughly five to eight mmHg systolic and three to four mmHg diastolic in people with hypertension or prehypertension, and small reductions in self-reported stress and anxiety are reported by a meta-analysis of breathwork trials and by one 12-week randomized trial.

Limits of the treatment claim

The evidence stops well short of a treatment claim: the blood-pressure trials are small, short and heterogeneous, one of the three syntheses was null under a random-effects model with 90% heterogeneity, the stress meta-analysis covers breathwork as a class rather than slow paced breathing alone, and the 12-week randomized trial of slow breathing for anxiety had no non-breathing control arm.

Markers and breathing rate

Heart-rate variability is a physiological marker rather than a felt outcome and is reported separately here; increases are most consistent while the breathing is being practised, and one 12-week randomized trial found no significant change in heart-rate variability. Six breaths per minute is a rate that appears in trial protocols, but no retrieved synthesis identifies an optimal rate, dose or duration, and no trial shows fewer cardiovascular events or less medication use.

People practicing pranayama breathing exercises
EnergyFocusStress & wellbeing10–20 min · Easy · Free
Reviewed Sep 23, 2026
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Scientific evidence

What the research shows

Outcome assessments based on research, including its uncertainties and limitations.

Blood pressure (systolic and diastolic)

Finding: Benefit supportedCertainty: Moderatestudies found a benefit from doing this

Evidence basis: randomised trials

Three independent syntheses of randomized trials agree that regular slow breathing lowers blood pressure modestly.

Population: Adults with hypertension or prehypertension, or taking antihypertensive medication, in randomized trials of slow breathing or yogic breathing: 17 studies in Chaddha 2019 (including device-guided and pranayama-style protocols), 13 studies in 1,097 participants in Cheng 2026, and 7 randomized trials with 683 participants in Chidambaram 2026, which pooled pranayama (yogic breathing) practices.

Research details

Summary

Three independent syntheses of randomized trials agree that regular slow breathing lowers blood pressure modestly. A meta-analysis of 17 randomized studies of device-guided and non-device-guided slow breathing (at 10 or fewer breaths per minute, at least 5 minutes on at least 3 days per week, for at least 4 weeks) found systolic blood pressure reduced by -5.62 mmHg (95% CI -7.86 to -3.38) and diastolic by -2.97 mmHg (95% CI -4.28 to -1.66), with high heterogeneity in all analyses, and its authors concluded that slow breathing may be a reasonable first treatment for low-risk hypertensive and prehypertensive patients reluctant to start medication. A 2026 meta-analysis of 13 studies reported systolic mean difference -7.68 mmHg (95% CI -9.87 to -5.49), diastolic -4.02 mmHg (95% CI -5.44 to -2.60) and heart rate -1.15 bpm (95% CI -1.73 to -0.56). A separate 2026 meta-analysis of 7 randomized trials in 683 patients with hypertension found systolic blood pressure reduced with a standardized mean difference of -0.72 (95% CI -0.89 to -0.55) under a fixed-effects model, but the random-effects estimate was -0.75 (95% CI -1.55 to 0.06) and not statistically significant, with I2 = 90% and a prediction interval from -3.15 to 1.65; one included trial favoured the control group, and the heart-rate estimate comes from five of the seven trials (439 participants). Cheng 2026 pooled 13 studies in 1,097 participants with I2 = 82% for systolic and 73% for diastolic pressure, and its included arms were not all slow-paced breathing, since it also pooled relaxation plus meditation, mindfulness meditation and 90 minutes a week of yoga breathing.

Why this certainty

Rated Moderate: three syntheses of randomized trials, two of them restricted to slow breathing, agree on the direction and on a modest magnitude, and blood pressure is measured objectively rather than by self-report, which limits detection bias. It is not rated Strong because the underlying trials are small and short, the largest synthesis reports high heterogeneity across all analyses, heterogeneity is high (I2 = 82% for Cheng's systolic estimate and 90% for Chidambaram's random-effects systolic estimate), one synthesis's random-effects estimate was null, one synthesis uses a fixed-effects model for its headline systolic result, its included arms were not all slow-paced breathing, retrieved trials lowered office but not 24-hour ambulatory pressure, and no evidence links the reduction to clinical events.

Limitations

The 2019 meta-analysis states that heterogeneity was high for all analyses, and its included trials were small and of at least four weeks only, with participant blinding impossible for a breathing intervention and with device-guided protocols carrying unavoidable attention and expectancy effects. Cheng 2026 pooled 13 studies in 1,097 patients with I2 = 82% (systolic) and 73% (diastolic) and its included arms were not all slow breathing. Chidambaram 2026 reports I2 = 90% and a prediction interval from -3.15 to 1.65, with one included trial favouring control. The pranayama review pooled a family of yogic breathing practices rather than one standardized slow-breathing protocol, and it reports the systolic effect only under a fixed-effects model, which is not the more conservative choice. No retrieved trial tested whether blood-pressure reduction translated into fewer cardiovascular events or less medication use. Retrieved trials that measured both settings found office blood pressure falling while 24-hour ambulatory pressure did not: in 10 untreated hypertensive men, eight weeks of device-guided slow breathing lowered office systolic and diastolic pressure and heart rate but not 24-hour pressure (Hering 2013); in 40 adults with prehypertension or stage 1 hypertension, four weeks of device-guided breathing lowered clinic resting pressure and mid-day ambulatory systolic pressure in women only, with no change in 24-hour pressure (Anderson 2010); and a third trial in 30 hypertensive patients found no difference from an active control at all (Altena 2009).

Effect estimate

Systolic blood pressure -5.62 mmHg (95% CI -7.86 to -3.38) and diastolic -2.97 mmHg (95% CI -4.28 to -1.66) across 17 randomized studies (Chaddha 2019). Systolic mean difference -7.68 mmHg (95% CI -9.87 to -5.49), diastolic -4.02 mmHg (95% CI -5.44 to -2.60) and heart rate -1.15 bpm (95% CI -1.73 to -0.56) across 13 studies (Cheng 2026). Systolic SMD -0.72 (95% CI -0.89 to -0.55) under a fixed-effects model, but -0.75 (95% CI -1.55 to 0.06) and non-significant under a random-effects model with I2 = 90%, across 7 randomised trials in patients with hypertension; heart-rate SMD -0.43 (95% CI -0.52 to -0.34, I2 = 0%) from 5 of those trials (439 participants) (Chidambaram 2026).

Sources for this outcome:

Perceived stress and anxiety (self-reported)

Finding: Benefit supportedCertainty: Limitedstudies found a benefit from doing this

Evidence basis: randomised trials

Self-reported stress and anxiety are lower after breathwork and slow-breathing practice, with small pooled effects.

Population: Adults in randomized and controlled studies of breathwork and slow breathing: 785 adult participants in 12 randomized trials for self-reported stress, 20 trials for anxiety and 18 for depressive symptoms (Fincham 2023, general adult populations); 15 studies of slow breathing below 10 breaths per minute in healthy subjects (Zaccaro 2018); and 100 adults with PROMIS Anxiety of 45 or above in a 12-week randomized single-blinded trial of yoga-based slow breathing who reached an average of slightly less than 3 breaths per minute (Birdee 2023).

Research details

Summary

Self-reported stress and anxiety are lower after breathwork and slow-breathing practice, with small pooled effects. A meta-analysis of randomized controlled trials whose primary outcome was self-reported stress pooled 12 trials with 785 adult participants and found a small-to-medium effect, Hedges g = -0.35 (95% CI -0.55 to -0.14, p = 0.0009), with intermediate heterogeneity (I2 = 42%), and most included studies were judged at moderate risk of bias; the same review found anxiety g = -0.32 (p < 0.0001, 20 trials) and depressive symptoms g = -0.40 (p < 0.0001, 18 trials). A systematic review restricted to slow breathing below 10 breaths per minute, covering 15 studies in healthy subjects, reports reduced symptoms of arousal, anxiety, depression, anger and confusion together with increased comfort, relaxation, pleasantness, vigour and alertness, but reports no pooled estimate. In a 12-week randomized single-blinded trial of 100 adults with PROMIS Anxiety of 45 or above, slow breathing reduced psychological stress on the PROMIS Anxiety scale by -4.85 points overall (by arm -5.37, 95% CI -7.24 to -3.49 and -4.30, 95% CI -5.60 to -3.00), while the comparison between a longer exhale and an equal exhale produced only a small, non-significant difference (d = 0.2). The same meta-analysis found a significant effect of breathwork on stress in nonclinical samples but not in mental health or physical health populations, and its risk-of-bias profile was starker than a 'mostly moderate' summary suggests: three of its twelve trials were at high risk of bias overall and the remaining nine raised some concerns.

Why this certainty

Rated Limited: the direction is consistent across a meta-analysis of randomized trials with a statistically precise small effect, a systematic review restricted to slow breathing, and a 12-week randomized trial, and the effect size is small and plausible rather than implausibly large. It is not rated higher because the meta-analytic estimate is for breathwork generally rather than slow paced breathing specifically, the slow-breathing-specific review offers no pooled estimate, the randomized trial of slow breathing lacked a non-breathing control, and all outcomes are self-reported. This is a felt outcome and is deliberately reported separately from the heart-rate variability outcome.

Limitations

The pooled meta-analytic estimate covers breathwork as a class, including techniques other than slow paced breathing, so it is indirect for this habit, and the authors themselves urge caution and call for low risk-of-bias designs to avoid a miscalibration between hype and evidence. The slow-breathing-specific synthesis reports a narrative summary with no pooled effect size and only 15 studies, all in healthy subjects. The 12-week randomized trial randomized participants to two slow-breathing ratios and had no non-breathing control arm, so the fall in anxiety cannot be separated from time, attention, expectancy or natural fluctuation, and its between-group difference for the breathing ratio was small and not statistically significant. Neither trial-based nor pooled evidence could be blinded, since participants know whether they are breathing slowly. Participants in that trial averaged slightly less than 3 breaths per minute by week 12, so it does not support the six-breaths-per-minute rate quoted elsewhere in this entry.

Effect estimate

Self-reported stress g = -0.35 (95% CI -0.55 to -0.14, z = 3.32, p = 0.0009, I2 = 42%, 12 randomized trials, 785 participants); self-reported anxiety g = -0.32 (p < 0.0001, 20 trials); depressive symptoms g = -0.40 (p < 0.0001, 18 trials) (Fincham 2023). PROMIS Anxiety fell over 12 weeks of slow breathing by -4.85 points overall (n = 100; by arm -5.37, 95% CI -7.24 to -3.49 and -4.30, 95% CI -5.60 to -3.00), with a non-significant between-group difference for exhale longer than inhale versus equal (d = 0.2) (Birdee 2023).

Sources for this outcome:

Heart-rate variability and autonomic markers (physiological marker, not a felt outcome)

Finding: Mixed evidenceCertainty: Limitedstudies disagree, or the effect depends on who is studied

Evidence basis: randomised trials

Slow breathing is consistently associated with higher vagally-mediated heart-rate variability while it is being practised, but the evidence is inconsistent once the breathing stops.

Population: Mixed populations across 223 studies in the largest meta-analysis, which does not report participant totals in its abstract; healthy subjects in the 15-study systematic review of breathing below 10 breaths per minute; patients with hypertension in the 13-study and 7-trial meta-analyses; 100 healthy adults over 12 weeks of slow breathing; and 40 physically active university students (25 male, 15 female, mean age 20.95 years) in a post-exercise randomized crossover trial.

Research details

Summary

Slow breathing is consistently associated with higher vagally-mediated heart-rate variability while it is being practised, but the evidence is inconsistent once the breathing stops. A systematic review and meta-analysis of 223 studies (172 measuring during the session, 16 immediately after a single session, and 49 after a multi-session intervention) reported increases in vagally-mediated heart-rate variability in all three windows, and concluded that voluntary slow breathing could be advised as a low-tech, low-cost technique for prevention and adjunct treatment with few adverse effects expected; its abstract reports no numerical effect sizes. A systematic review of 15 studies of slow breathing below 10 breaths per minute in healthy subjects likewise reports increased heart-rate variability and respiratory sinus arrhythmia alongside increased EEG alpha and decreased theta power. In patients with hypertension, a meta-analysis found the low-frequency to high-frequency power ratio reduced by -1.09 (95% CI -1.94 to -0.23, p = 0.01) across three studies, a result the authors' own leave-one-out analysis found unstable, and a separate meta-analysis of 7 randomized trials described heart-rate variability improvements as modest. Against this, a 12-week randomized trial of slow breathing in 100 healthy adults found no significant change in heart-rate variability despite a fall in self-reported anxiety, and in a randomized crossover trial of 40 physically active university students, six-breaths-per-minute breathing after high-intensity interval training left heart rate lower than box breathing (154.77 +/- 12.18 versus 164.65 +/- 9.40 bpm) without a significant difference in time to recovery.

Why this certainty

Rated Limited and recorded as Mixed/uncertain. A very large meta-analysis reports increased vagally-mediated heart-rate variability across all three measurement windows, and two further syntheses report directionally consistent autonomic findings, but the largest review provides no pooled numerical estimate, the most robust effects are the ones measured during slow breathing itself, which the breathing pattern mechanically influences, and the longer-term picture is genuinely inconsistent because a 12-week randomized trial found no change in heart-rate variability. Because this is a physiological marker rather than a felt outcome, it was graded on its own and kept separate from the self-reported stress and anxiety outcome.

Limitations

The largest synthesis reports increases without numerical effect sizes, so the magnitude of the autonomic change could not be verified, and its multi-session intervention evidence rests on 49 studies of heterogeneous duration and protocol. The most consistent increases are those measured while the participant is breathing slowly, and the review deliberately separates during-breathing, immediately-after and after-intervention windows, so a substantial part of the during-breathing increase is expected to reflect the mechanics of slower, deeper breathing rather than a durable shift in autonomic tone; the retrieved abstract does not quantify how much of the effect persists. Evidence after practice ends is inconsistent: one 12-week randomized trial found no change in heart-rate variability and a meta-analysis of pranayama trials called heart-rate variability improvements modest. Populations differ substantially (healthy adults, hypertensive patients, athletes after exercise), and the post-exercise heart-rate finding comes from a single small crossover trial with no clinical endpoints. Heart-rate variability is a physiological marker rather than something a person feels, so it is reported separately from the stress and anxiety outcome, and one retrieved narrative review notes that direct evidence for several proposed mechanisms in humans is still lacking.

Effect estimate

Low-frequency to high-frequency power ratio mean difference -1.09 (95% CI -1.94 to -0.23, p = 0.01) across 3 studies, a result the authors' own leave-one-out analysis found unstable (Cheng 2026). Post-exercise heart rate after high-intensity interval training 154.77 +/- 12.18 bpm with six breaths per minute (5 seconds in, 5 seconds out) versus 164.65 +/- 9.40 bpm with box breathing (p < 0.001, Cohen's d = 0.907), with no significant difference in recovery time (p = 0.128), in 40 physically active university students (Kasap 2025). The Laborde 2022 meta-analysis of 223 studies reports no numerical effect sizes in its abstract.

Sources for this outcome:

What people say

Who discusses this?

Public statements, with positions specific to each source and topic. These views do not determine the scientific evidence assessment.

What the research shows ↑

No sourced public statements added for this habit yet. This does not mean no one discusses it.

Practical steps and precautions

How to try it

  1. Sit comfortably and breathe through the nose at a slow, steady pace you can hold without straining; six breaths per minute, about five seconds in and five seconds out, is a commonly cited resonance rate and the rate tested in acute protocols such as Kasap 2025 and in the protocol table of Sharma 2026 (four to six breaths per minute); it is an editorial starting point rather than a validated optimal dose.
  2. Keep the exhale relaxed rather than forced; extending the exhale is widely taught, but the one retrieved trial that compared a longer exhale with an equal exhale found no statistically significant difference in stress reduction.
  3. Practise for roughly ten to twenty minutes, once or twice daily: that is the dose given for slow breathing at four to six breaths per minute in a retrieved review's protocol table (Sharma 2026), while five minutes is the minimum session length in the blood-pressure trials' inclusion criteria rather than a tested target; one trial delivered 12 weeks of supervised plus home practice, and no meta-analysis established an optimal duration or frequency.
  4. Use a pacer tone, a counting rhythm or an app if it helps you hold the pace, and treat the practice as an addition to, not a replacement for, any prescribed treatment.

Precautions

  • Do not use slow breathing instead of prescribed blood-pressure medication; the pooled trials studied low-risk hypertensive and prehypertensive adults, including as an option for people reluctant to start medication, and no retrieved trial tested slow breathing as a replacement for existing drug treatment.
  • Stop a session if you feel light-headed, dizzy or short of breath, and return to normal breathing; the largest synthesis expected few adverse effects (Laborde 2022), and the retrieved 12-week trial recorded 30 adverse events, of which 12 occurred during classes and were related to slow breathing, including lightheadedness in 9 participants.
  • Treat breathing practices with caution and seek clinical advice first if you have panic symptoms, significant heart or lung disease, or are pregnant, because a retrieved narrative review lists these as populations requiring caution.
  • Expect a modest effect at most: the hypertension syntheses report average reductions in blood pressure and no trial shows fewer cardiovascular events, fewer hospital admissions or less medication use.

References

Device and non-device-guided slow breathing to reduce blood pressure: A systematic review and meta-analysis

Chaddha A, Modaff D, Hooper-Lane C, Feldstein DA · Complementary Therapies in Medicine · 2019

Systematic review and meta-analysis of randomized controlled trials and first phases of randomized cross-over studies, using the Cochrane Risk of Bias Tool and DerSimonian and Laird random-effects modelsVerified from abstract
Open original source

Voluntary Slow Breathing Exercise on Cardiovascular Parameters in Patients With Hypertension: A Systematic Review and Meta-Analysis

Cheng S, Chen Y, Yu M, Zhao L, Huang H, Zhao M · Clinical Cardiology · 2026

Systematic review and meta-analysis of studies in hypertensive patients, following PRISMA, with pooling in RevMan 5.4 using mean differences and fixed-effects or random-effects models according to the heterogeneity testVerified from abstract
Open original source

The effect of yogic breathing (Pranayama) on heart rate and blood pressure in patients with hypertension: A systematic review and meta-analysis

Chidambaram Y, Saravana Kumar P, Gunasekar S, Kundoor LR, Kuppusamy M, Kasi M, Chandrasekaran AM, Shanmugasundaram S, Ramesh S, Sadagopan T, Naik N, Roy A, Prabhakaran D, Senguttuvan NB · Indian Heart Journal · 2026

Systematic review and meta-analysis of randomized controlled trials in patients with hypertension, following PRISMA with Cochrane RoB 2 assessment and pooled standardized mean differences (PROSPERO CRD42024597502)Verified from abstract
Open original source

Effects of acute and long-term slow breathing exercise on muscle sympathetic nerve activity in untreated male patients with hypertension.

Hering D, Kucharska W, Kara T, Somers VK, Parati G, Narkiewicz K · Journal of hypertension · 2013

Randomized controlled trial of device-guided slow breathing with matched controlsVerified from abstract
Open original source

Regular slow-breathing exercise effects on blood pressure and breathing patterns at rest.

Anderson DE, McNeely JD, Windham BG · Journal of human hypertension · 2010

Randomized controlled trial of device-guided slow breathingVerified from abstract
Open original source

Effect of device-guided breathing exercises on blood pressure in patients with hypertension: a randomized controlled trial.

Altena MR, Kleefstra N, Logtenberg SJ, Groenier KH, Houweling ST, Bilo HJ · Blood pressure · 2009

Randomized single-blind controlled trialVerified from abstract
Open original source

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

Fincham GW, Strauss C, Montero-Marin J, Cavanagh K · Scientific Reports · 2023

Systematic review and meta-analysis of randomized controlled trials of breathwork, using random-effects models with self-reported/subjective stress as the primary outcomeVerified from abstract
Open original source

How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing

Zaccaro A, Piarulli A, Laurino M, Garbella E, Menicucci D, Neri B, Gemignani A · Frontiers in Human Neuroscience · 2018

Systematic review (PRISMA) of studies of slow breathing techniques below 10 breaths per minute in healthy subjects, with narrative synthesis and no meta-analysisVerified from abstract
Open original source

Slow breathing for reducing stress: The effect of extending exhale

Birdee G, Nelson K, Wallston K, Nian H, Diedrich A, Paranjape S, Abraham R, Gamboa A · Complementary Therapies in Medicine · 2023

12-week randomized, single-blinded trial of 100 participants comparing yoga-based slow breathing with exhale greater than inhale versus exhale equal to inhale in healthy adults; both arms received slow breathing, so there was no non-breathing control groupVerified from abstract
Open original source

Effects of voluntary slow breathing on heart rate and heart rate variability: A systematic review and a meta-analysis

Laborde S, Allen MS, Borges U, Dosseville F, Hosang TJ, Iskra M, Mosley E, Salvotti C, Spolverato L, Zammit N, Javelle F · Neuroscience and Biobehavioral Reviews · 2022

Systematic review and meta-analysis of studies of voluntary slow breathing, separating heart-rate variability measured during the breathing session, immediately after one session, and after a multi-session interventionVerified from abstract
Open original source

Box breathing or six breaths per minute: Which strategy improves athletes post-HIIT cardiovascular recovery?

Kasap M, Aydin GR · PLOS ONE · 2025

Randomized crossover trial comparing three recovery breathing protocols during three high-intensity interval training sessions in 40 physically active university studentsVerified from abstract
Open original source

Neurophysiological mechanisms of breathing-based well-being practices: a narrative review for clinical application

Sharma P, Veerareddy V, Hong I, Nycklemoe M, Kandimalla M, Sharma V, Kung TL, Osman R, Lim S, Kandimalla KK, Lapid MI, Min PH · Frontiers in Psychiatry · 2026

Narrative review (no systematic search or meta-analysis) of physiological mechanisms of breathing-based well-being practices; cited here only for mechanistic framing and safety populations, not for effect estimatesVerified from abstract
Open original source

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Editorial history and review method

Revision 4 · Approved for publication · Codex (publication approval explicitly authorized by site owner; category migration)

Prepared and checked with AI. Publication approval does not imply independent expert review. Request a correction.

Applied the group-1 audit's numbers. blood-pressure now reports Chidambaram 2026's random-effects null for systolic pressure (SMD -0.75, 95% CI -1.55 to 0.06, I2 = 90%, prediction interval -3.15 to 1.65, one trial favouring control) beside the fixed-effects estimate, states that its heart-rate estimate comes from 5 of the 7 trials (439 participants), records Cheng 2026's 1,097 participants with I2 = 82%/73% and its mixed-intervention pool, and adds three trials that lowered office but not 24-hour ambulatory pressure (Hering 2013, Anderson 2010) or found no effect against an active control (Altena 2009). heart-rate-variability-and-autonomic-markers corrects the LF/HF estimate from 13 studies to 3 and records that the authors' own leave-one-out analysis found it unstable. perceived-stress-and-anxiety corrects the Birdee 2023 confidence-interval attribution, records both arm-specific intervals, the achieved dose of slightly less than 3 breaths per minute, the Fincham subgroup nuance and risk-of-bias distribution. Implementation now states the Sharma 2026 protocol dose (10-20 minutes, four to six breaths per minute) and stops calling five minutes a tested target; precaution 2 records the 12-week trial's 30 adverse events, 9 of them lightheadedness. The card summary was also completed: it had been truncated mid-word at 218 characters. Second reviewer must re-check: (a) whether Altena 2009 and Anderson 2010 are among Chaddha 2019's 17 studies, which cannot be established while Chaddha's full text is paywalled; (b) whether Moderate certainty survives I2 = 82% plus Cheng's mixed-intervention pool; (c) whether the six-breaths-per-minute alias belongs in the catalogue at all, since it is supported as a resonance rate but no retrieved synthesis identifies it as optimal. Publication release 2026-10-04: site owner authorized a bounded AI audit and release of this exact revision. See docs/release-audit-2026-10-04.md for source-check findings and limits. No independent health-professional or peer review is claimed. Category migration 2026-10-04: removed the separate goals field; categories: Energy, Focus → Energy, Focus, Stress & wellbeing. Research assessments, sources, guidance, precautions, and evidence review dates are unchanged. This revision awaits publication approval; no new evidence review is claimed. Publication approval 2026-10-04: site owner explicitly accepted all current category-migration revisions for deployment and requested that remaining limitations be retained in docs/content-review-backlog.md. Approval applies to this exact content revision. No new evidence review, independent expert review, or clinical validation is claimed; existing precautions and disclosures remain in effect.