Yoga for hypertension and prehypertension

The effect

Systolic −7.95 mmHg (95% CI −10.24 to −5.66), diastolic −4.93 mmHg, heart rate −4.43 bpm versus waitlist control. 30 RCTs, 2,283 participants (PLOS One, 2025).

The comparator that matters

Versus no treatment: clear benefit (SBP −7.96 mmHg). Versus exercise: no significant difference. Yoga is not superior to exercise for blood pressure. It is an alternative that some people will sustain when they would not sustain a gym.

The dose that worked

Full practice — posture, breath, and meditation together — produced SBP −8.17 mmHg. Limited interventions using only some elements showed no significant reduction. 8 to 12 weeks in most trials.

What we do not know

The 30-RCT meta-analysis graded its own evidence as very low quality despite the effect size. Trials cannot be blinded. Long-term maintenance is largely unstudied. Real-world observational data suggests smaller effects than trials (SBP ≈ −2.6 mmHg in normotensive populations).

Adjunct only. Does not replace antihypertensive medication. Patients should not alter prescribed therapy without their physician.

Yoga for chronic non-specific low back pain

The effect

Small improvement in back-specific function versus no exercise (MD −1.69 on a 0–23 scale, low certainty). Probably a small improvement in physical and mental quality of life (moderate certainty). Cochrane 2022 (CD010671.pub3).

The comparator that matters

Cochrane: probably little or no difference between yoga and other back-focused exercise at three months. The choice between them may reasonably come down to availability, cost, and patient preference.

Adverse events — read this

Yoga is associated with more adverse events than no exercise — most commonly an increase in back pain. Risk appears comparable to other back-focused exercise, and no serious adverse events were identified. But it is not zero, and patients should be told.

What we do not know

The pain reduction did not meet predefined thresholds for minimum clinical importance. Cochrane notes that because no sham-yoga trials exist and all studies were unblinded, it is unlikely a blinded comparison would find a clinically important benefit. No evidence on work-related disability.

Coherent breathing · 5.5 breaths per minute

The mechanism

Breathing near 5.5 breaths per minute approaches the cardiovascular system’s resonance frequency, aligning respiratory and Mayer wave rhythms and maximising heart rate variability and baroreflex sensitivity (Lehrer et al., 2003; Bernardi et al., Circulation 2001).

Dose

5 minutes daily as a floor. Longer sessions used in HRV biofeedback protocols. No contraindications identified for normotensive or hypertensive adults at rest.

What we do not know

Acute HRV change is well established. Whether sustained practice produces durable clinical outcomes — and at what dose — is far less settled. HRV is a proxy, not an outcome. It is not yet clear how much of the benefit is specific to 5.5 bpm versus slow breathing generally.

Physiological sigh · cyclic sighing

The effect

Double inhale through the nose, long exhale through the mouth. Balban et al. (Cell Reports Medicine, 2023) found cyclic sighing produced greater improvement in mood and reduced respiratory rate than mindfulness meditation over 28 days of brief daily practice.

What we do not know

A single well-conducted trial. Not yet replicated independently. The comparison was against other brief practices, not against no intervention or against pharmacological treatment. Promising, not established.

Correction · July 2026

Yoga Nidra / NSDR

This entry previously stated a 65% dopamine increase during Yoga Nidra, citing Kjaer 2002. That figure circulates widely and we repeated it without checking. On review, it does not hold up as stated, and we have corrected it.

What the study actually found

Kjaer et al. (2002) scanned eight experienced practitioners using 11C-raclopride PET and observed roughly an 8% decrease in binding potential in the ventral striatum during Yoga Nidra — indicating increased endogenous dopamine signalling. The widely-quoted 65% figure is a value calculated from that binding change, not a directly measured increase. A 2020 review of the yoga neuroimaging literature notes this remains the only study of its kind. In twenty-four years it has not been replicated.

The honest case for the practice

It rests on adherence, not neurochemistry. Yoga Nidra requires no effort, no mobility, no flexibility, and no prior training. You lie down and follow a voice. For a patient who is exhausted, deconditioned, in pain, or newly post-operative, it is often the only practice they will actually do — and a practice performed daily beats a superior practice abandoned in a week. That is the argument, and it does not need a dopamine statistic to stand up.

What we do not know

Almost everything. The dopamine finding is unreplicated. Trials on stress, sleep, and wellbeing are small and mostly unblinded. There is no established dose-response. Treat every mechanistic claim about Yoga Nidra — including ours — as preliminary.

Safety note · Ashwagandha

The NIH LiverTox database classifies ashwagandha as a likely cause of clinically apparent liver injury and advises against its use in patients with cirrhosis or advanced chronic liver disease. Most reported cases are mild-to-moderate and resolve on discontinuation, but acute liver failure has been described, and injury has occurred in healthy young adults at labelled doses. Bioveda does not recommend ashwagandha supplementation, and any patient using it should tell their physician.