Written by Artyom Sklyarov · Co-founder, SUUR · Updated 2026-09-19

The physiological sigh is a breath pattern you already do without deciding to: a deep inhale, a short second inhale on top, then a long, slow exhale. Spontaneous sighs are ordinary breathing, not a technique. The research that describes them says they happen every few minutes to reinflate the lungs’ alveoli, and that sighing increases under hypoxia, stress and certain psychiatric conditions.

What’s new is doing it deliberately. Andrew Huberman has popularized the pattern as an on-demand calming tool. The controlled evidence for the deliberate version is one 2023 Stanford trial, and it tested something narrower than the popular version: five minutes of repeated sighing a day, for a month. It did not test a single sigh as an in-the-moment reset. Keep that distinction in mind for the rest of this page.

The protocol

Inhale through the nose until your lungs feel about 80% full.
Take a second short inhale on top — a quick top-up at the peak. It is normal for the second inhale to be shorter than the first.
Exhale slowly through the mouth until you’re completely empty. The exhale should last roughly twice as long as the combined inhale.
Repeat. The popular version is one to three cycles. The version the Stanford trial tested was continuous repetition for five minutes.

One to three cycles takes about 30 seconds. You can do it anywhere — at your desk, in a parked car, in a meeting if you’re subtle.

Why the double inhale matters

Most calming protocols emphasize the exhale. The physiological sigh adds a specific inhale shape: the short second inhale on top of the first. The popular explanation is that it reopens collapsed alveoli — the small air sacs in the lungs — and that explanation comes from the spontaneous-sigh literature, where reinflating alveoli is the stated function of the sighs we take every few minutes.

What that literature did not do is test the deliberate version. In 2016, a team from Jack Feldman’s lab at UCLA and Mark Krasnow’s at Stanford identified, in mice, a small peptide-signalling circuit that feeds the preBötzinger complex — the brainstem’s breathing rhythm generator. Blocking both of its receptors abolished basal sighing. It is a finding about where sighs come from, not about what a voluntary double inhale does for a stressed adult.

“Sighs also occur spontaneously every few minutes to reinflate alveoli, and sighing increases under hypoxia, stress, and certain psychiatric conditions.”

Li et al., 2016 · The peptidergic control circuit for sighingNature, 530(7590):293–297

The Stanford authors offer their own reading of why cyclic sighing did well in their trial: it differed from the other groups in its extended exhale and in the double inhale, which increases the depth of inhalation. That is the authors’ hypothesis. The trial did not isolate either component.

The Stanford 2023 study

In 2023, a team led by Melis Yilmaz Balban, David Spiegel and Andrew Huberman at Stanford ran a remote randomized controlled trial of three daily five-minute breathwork practices against five minutes of mindfulness meditation, for one month: cyclic sighing (the physiological sigh, repeated for the full five minutes), box breathing, and cyclic hyperventilation with retention (Wim Hof-style). 108 participants were enrolled and randomized.

The result: breathwork as a group, and cyclic sighing in particular, produced greater improvement in mood and a greater reduction in respiratory rate than mindfulness meditation. The abstract reports its significant comparisons against meditation, not against the other breathing protocols. It is one trial, remote, small per arm and a month long. The authors conclude that daily five-minute cyclic sighing “has promise as an effective stress management exercise” — the right strength of claim for one trial.

“Using a mixed-effects model, we show that breathwork, especially the exhale-focused cyclic sighing, produces greater improvement in mood (p < 0.05) and reduction in respiratory rate (p < 0.05) compared with mindfulness meditation.”

Balban et al., 2023 · Brief structured respiration practices enhance mood and reduce physiological arousalCell Reports Medicine, 4(1):100895

Two ways to use it

1. Acute (1–3 cycles).The popular use: before a presentation, after a frustrating email, in the middle of an argument. It is the application most people learn first, and the one with the least direct evidence — the Stanford trial did not test it. If you use the sigh this way, you are going on how it feels to you, not on a trial result.

2. Daily practice (5 minutes). Repeated cycles for five minutes a day. This is the dose the Stanford trial actually tested, and the only one its mood and respiratory-rate results apply to. Pick a fixed time of day and keep it.

Where it fits relative to other techniques

The physiological sigh’s practical advantage is size: a cycle takes about ten seconds and needs no counting, which makes it the easiest of these patterns to reach for in the middle of a day. Whether one to three breaths produce a measurable effect is the open question above.

For comparison:

4-7-8 takes just over a minute for four cycles and asks you to hold a count most people have to learn.
Box breathing takes 80 seconds for five cycles. It was one of the other arms of the Stanford trial.
Resonance breathing takes 3–10 minutes a session and is studied as a practice repeated over weeks — a different timescale entirely. A 2022 meta-analysis of 223 studies found increases in vagally-mediated HRV during slow breathing, immediately after a single session, and after multi-session interventions.

If you want one breath pattern with a randomized trial behind it, this is a reasonable one to learn — as the daily five minutes that was actually tested. If you want a daily practice studied over weeks, learn resonance breathing. You can use both: the sigh for the moment, resonance for the routine.

Common mistakes

Skipping the second inhale.Without the short top-up, you’re doing extended-exhale breathing — a different pattern from the one the Stanford trial tested.
Making the exhale too fast.The exhale should be roughly twice as long as the combined inhale. If you’re puffing it out in 2 seconds, you’re not doing the protocol. Aim for 4–6 seconds of exhale per cycle.
Pushing through lightheadedness. Repeated deep inhalation can make you lightheaded. If it does, stop and breathe normally.
Forcing it during a panic attack.If you’re mid-panic, the deep inhalation can feel unreachable. Don’t force it: drop the inhale shape and just lengthen the exhale, or breathe normally. If panic attacks recur, that is a conversation for a clinician, not a breathing page.