Cyclic Sighing vs Box Breathing vs Mindfulness: What Stanford’s RCT Found

In 2023, a research team at Stanford published one of the most carefully designed studies on breathwork to date — a randomised controlled trial comparing three different 5-minute daily breathing techniques against mindfulness meditation over four weeks. The results have practical implications for anyone trying to choose a stress management or mood practice.

The Study Design

Published in Cell Reports Medicine and led by Yilmaz Balban and colleagues, the trial enrolled participants who were randomly assigned to one of four daily 5-minute practices: (1) cyclic sighing, which emphasises prolonged exhalations; (2) box breathing, which uses equal durations for inhalation, breath retention, and exhalation; (3) cyclic hyperventilation with retention (similar in structure to Wim Hof breathing); or (4) mindfulness meditation — passive breath observation, the control condition. The study used wearable physiology tracking (heart rate, respiratory rate) and validated mood assessments throughout.

Key Results

All four practices improved mood and reduced anxiety compared to baseline. However, the three breathwork interventions outperformed mindfulness meditation on mood improvement and respiratory rate reduction. The standout finding was that cyclic sighing produced the largest and most consistent improvements in positive affect and the greatest reductions in respiratory rate — outperforming both box breathing and cyclic hyperventilation, as well as mindfulness.

The cyclic sighing technique involves a double nasal inhale (a full breath in through the nose, followed immediately by a brief supplementary sniff to fully inflate the alveoli), followed by a long, slow exhale through the mouth. It takes about 5 seconds to inhale and 8–10 seconds to exhale. The researchers believe the extended exhalation phase is the critical mechanism — it prolongs the parasympathetic phase of each heart rate variability cycle, effectively signalling “calm” to the autonomic nervous system more efficiently than the other methods.

Why Exhalation Duration May Be the Key Variable

Heart rate naturally rises slightly during inhalation and falls during exhalation — a phenomenon called respiratory sinus arrhythmia. Extending the exhalation phase therefore extends the period of heart rate deceleration, increasing vagal tone. This is not unique to cyclic sighing, but the technique optimises for this mechanism more directly than box breathing (which adds retention phases) or cyclic hyperventilation (which pushes the system in the opposite direction before the retention).

The study also found that breathwork, but not mindfulness, reduced resting respiratory rate — suggesting a physiological adaptation distinct from the mood effects. After four weeks, participants in the breathwork groups were breathing more slowly at rest than when they started.

What This Means in Practice

The study is significant because it used a controlled design to compare techniques that are commonly promoted individually, often with little comparative evidence. The practical takeaway is that just 5 minutes per day of deliberate breathing — particularly any technique emphasising extended exhalation — reliably improves mood and reduces anxiety, with cyclic sighing showing the strongest signal in this trial.

Box breathing (used in military and tactical performance contexts) and mindfulness meditation both produced benefits, but were not superior to cyclic sighing in this study’s population. For someone choosing a starting practice, this evidence favours simplicity: a double inhale through the nose, long exhale through the mouth, repeated for five minutes.

Study Details

Yilmaz Balban M et al. “Brief structured respiration practices enhance mood and reduce physiological arousal.” Cell Reports Medicine, 2023; 4(1):100895. PMC9873947. Source: PubMed, retrieved via PMC9873947.

This article summarizes current research for informational purposes. Always consult with your healthcare provider for personalized medical advice.