Sudarshan Kriya Yoga (SKY) is a structured breathing practice that has been studied more seriously than almost any other — including trials for depression, PTSD, and stress. In a landmark Indian study at NIMHANS, SKY was compared head-to-head with electroconvulsive therapy (ECT) and the antidepressant imipramine in patients with melancholic depression: its remission rate was lower than ECT but comparable to the antidepressant. Other trials report lower cortisol and reduced PTSD symptoms, including in military veterans. It's a striking body of evidence for a breathing technique — though, as we'll cover honestly, the overall quality is mixed and larger trials are still needed.
What Sudarshan Kriya is
SKY is not a single breath but a structured sequence, taught over several days and then practiced regularly. It integrates several elements in a set order:
- •Ujjayi ("victorious breath") — very slow breathing with a slight constriction of the throat that adds airway resistance and lengthens each phase of the breath.
- •Bhastrika — the fast, forceful "bellows breath" that energizes (see Bhastrika and the brain).
- •The Sudarshan Kriya itself — cyclical breathing in slow, medium, and fast rhythms.
- •Om chanting and guided attention.
The combination is deliberate: slow breathing to calm, fast breathing to activate, and rhythmic cycling between them — both families described in fast vs slow pranayama. It was popularized worldwide by the Art of Living organization.
The clinical evidence
The research on SKY is unusually ambitious for a breathing technique:
Depression, compared to standard treatments. In the NIMHANS trial (Janakiramaiah et al., 2000), SKY was compared with ECT and imipramine in melancholic depression. Remission was lower than with ECT but comparable to the antidepressant — a remarkable benchmark for a breathing practice. Smaller studies reported reduced depression scores, with hormonal changes, in alcohol-dependent patients.
PTSD. A trial among survivors of the 2004 Indian Ocean tsunami reported reductions in PTSD and depression. A small randomized study of US veterans of Iraq and Afghanistan found reduced PTSD symptoms and a lower respiration rate, with effects still present at one-year follow-up.
Stress hormones. Several studies report lower cortisol after SKY training, alongside reduced self-reported stress — consistent with the practice's calming slow-breathing core.
The honest caveats
This record deserves an honest frame. Systematic reviews conclude that while several trials report positive effects on mood and stress, the overall evidence is of mixed quality, and larger, well-controlled randomized trials are needed before firm conclusions. Many studies are small; some lack rigorous controls; some were run by researchers connected to the organization that teaches it. The NIMHANS comparison is striking but is one study, decades old. So the fair statement is: promising and unusually serious for breathwork, but not definitive. SKY is a supportive practice, not a replacement for treatment of depression or PTSD — anyone with those conditions should work with a professional.
Why it might work
Several mechanisms are proposed. The slow Ujjayi component shifts the body toward parasympathetic dominance, amplifying the normal breath-linked rise and fall of heart rate (respiratory sinus arrhythmia) — the same lever as coherent breathing. The rhythmic, high-ventilation cycling adds a strong activating contrast. And the reported drop in cortisol points to a genuine shift in stress chemistry, not just a feeling of relaxation (see how to lower cortisol).
Practicing SKY
SKY is unusual among the techniques on this site in that it's taught, not self-learned. The full Sudarshan Kriya is traditionally learned in a structured course with a trained instructor, because it combines forceful and slow techniques in a specific sequence that's hard to reproduce from text. If you're drawn to it, the appropriate path is a proper course, then regular home practice. The gentler component — slow Ujjayi-style breathing — you can practice on your own. The fast parts carry the same cautions as Bhastrika: seated only, never in water or while driving, and not without medical advice if you have heart or lung conditions, uncontrolled blood pressure, or are pregnant.
See your body respond
The slow-breathing core of SKY is measurable. ONDA reads your pulse from your phone camera or Apple Watch, and your HRV from Apple Watch, so you can watch how slow Ujjayi-style breathing settles your heart and track whether your baseline shifts with regular practice.
Sources include Janakiramaiah et al., 2000 (Journal of Affective Disorders) and Seppälä et al., 2014 (Journal of Traumatic Stress). ONDA is a breathing and HRV biofeedback app, not a medical device. SKY is not a replacement for professional treatment of depression or PTSD.