The physiological sigh — a single breath to rapidly reduce stress

Take a double inhale through the nose followed by a long, slow exhale — the fastest single-breath reset of the stress response.

Why it works

The physiological sigh is a natural breathing pattern — a double inhale (nasal inhale, then a second shorter nasal inhale on top of it) followed by a long exhale — that humans and other mammals produce spontaneously to re-open collapsed alveoli. Research from Huberman’s group at Stanford found that deliberately practicing this pattern produces the fastest within-session reduction in physiological arousal and self-reported calm of several breathing techniques tested, including cyclic hyperventilation and mindfulness breathing.

How to do it

1. Inhale through the nose fully.
2. Without exhaling, take one shorter second inhale through the nose (double inhale).
3. Exhale fully and slowly through the mouth, emptying the lungs completely.
4. One to five repetitions is usually sufficient for a noticeable acute effect.

Evidence

A 2023 RCT from Stanford compared cyclic sighing, cyclic hyperventilation (Wim Hof style), box breathing, and mindfulness meditation over a month. Cyclic sighing produced the largest improvements in positive affect and respiratory rate and the largest reductions in anxiety of the techniques tested. (rct)

This is one RCT; the practice is promising but the evidence base is early. Results should not be extrapolated to clinical anxiety without further replication.

Sources

• Balban et al. (2023), brief structured respiration practices enhance mood and reduce physiological arousal, Cell Reports Medicine

Common mistake

Exhaling quickly rather than slowly — the slow, complete exhale is where the parasympathetic effect is concentrated. A fast exhale reduces the mechanism to two quick inhales.