Does the physiological sigh really calm you down?

The Physiological Sigh: How to Do It and What It Does

Reviewed 2026-10-25 · 6 sources · By Anthony Falcone

The short answer: The physiological sigh is two inhales through the nose, the second one short, followed by a long, slow exhale. In a randomised trial of 108 adults, doing it for 5 minutes a day for a month lifted mood more than mindfulness meditation and lowered breathing rate, but it eased anxiety no more than meditation did. It's free and promising, and the evidence is still thin.^1,6

Before you start

Talk to your doctor before starting breathing exercises if you have a heart or lung condition, epilepsy or seizures, glaucoma, a panic disorder or another mental health condition, or if you are pregnant. The trial behind this guide excluded people with heart disease, glaucoma, seizures, pregnancy and serious psychiatric conditions, so its results don't cover them.¹
Breathing exercises don't replace care. If anxiety, panic attacks or breathlessness are frequent or getting worse, see a doctor. Sighing far more often than normal is linked to over-breathing and symptoms of its own.⁶
Stop and go back to normal breathing if an exercise makes you dizzy, tingly or short of breath.

5 min a day for 28 days: the dose of cyclic sighing tested in the Stanford trial¹
108 adults enrolled in that trial, 30 of them in the cyclic sighing group¹
3.85 points average drop in state anxiety per cyclic sighing session, on a 20–80 scale (meditation: 3.95)¹
2.4× the size of a natural sigh compared with a normal breath, on average, in healthy adults during quiet sleep⁶
12 trials with 785 adults: breathwork lowered stress by a small-to-medium amount compared with no breathwork²

What is the physiological sigh?

A sigh is a deep breath your body takes on its own every few minutes. It is more than twice the size of a normal breath, and it re-inflates tiny air sacs in the lungs that have started to collapse, which keeps the lungs supple.⁵

Natural sighs sometimes come as one inhale stacked on another. In healthy adults during quiet sleep, sighs averaged 2.4 times the volume of normal breaths, with a slightly longer inhale and exhale.⁶

The breathing exercise copies that pattern on purpose: a deep inhale, a second short inhale on top, then a long exhale. Repeated for several minutes, researchers call it cyclic sighing, and it is the version that has been tested.¹

How to do a physiological sigh

In the Stanford trial, people sat or lay down and set a timer for 5 minutes. They breathed in slowly through the nose and, once the lungs felt full, took one more breath in to fill them completely. Then they breathed out slowly and fully, ideally through the mouth, and repeated the pattern until the timer ended.¹

The second inhale is usually shorter and smaller than the first; that is normal. People who preferred it were allowed to breathe entirely through the nose.¹

Why a long exhale? Breathing in speeds the heart up slightly and breathing out slows it down. A systematic review of slow-breathing studies, at under 10 breaths a minute, found slow breathing raised heart rate variability and went with feeling more relaxed, more alert and less anxious.^1,4

What the research shows

The main study is a randomised trial at Stanford University. 108 adults, most of them recruited from an undergraduate class, were assigned to one of three 5-minute breathing exercises or to 5 minutes of mindfulness meditation, once a day for a month. 30 did cyclic sighing; the others did box breathing, fast breathing with breath holds, or meditation.¹

Every group felt less anxious and less negative straight after their sessions. With cyclic sighing, state anxiety fell by an average of 3.85 points per session on a 20–80 scale, about the same as with meditation (3.95 points). On anxiety, it did no better than meditation.¹

Where cyclic sighing stood out was positive mood. It raised positive feelings more than meditation did, and the gap grew the more days people kept practising. The other two breathing exercises also did better than meditation, but not by a statistically significant margin.¹

Over the month, daily breathing rate, measured by a wrist wearable, fell more in the cyclic sighing group than in the meditation group, and the people whose breathing rate fell most tended to gain the most in positive mood. Heart rate variability, resting heart rate and sleep didn't change in any group.¹

Physiological sigh vs box breathing

Box breathing means equal counts of breathing in, holding, breathing out and holding. In the Stanford trial it cut state anxiety by about as much per session as cyclic sighing (3.75 vs 3.85 points), but its lift in positive mood was not significantly bigger than meditation's. The groups were too small to compare the breathing exercises directly with each other.¹

A 2026 randomised trial in 62 cadets tested both right after an all-out exercise test. Compared with normal breathing, cyclic sighing and box breathing both sped up the return of high-frequency heart rate variability, a sign of the calming side of the nervous system. Heart rate came down at the same pace in all three groups.³

Across breathing techniques in general, slow ones have the better evidence. In a meta-analysis of randomised trials, the 10 trials of slow-paced breathing showed a significant drop in stress, while the 2 trials of fast-paced breathing did not reach significance.²

Does one sigh work, or do you need minutes?

The tested dose is minutes, not a single breath. The Stanford results are changes from just before to just after a 5-minute session, repeated daily. People in the breathing groups did their exercise on about 20 of the 28 days on average (19.61), and the mood benefit of cyclic sighing grew with the number of days they had done it.¹

A spontaneous sigh is a normal reflex, and in lab studies muscle tension dropped after one, especially in people high in anxiety sensitivity. But a deep breath taken on command did not show that physical relief effect, so a natural sigh and a deliberate one may not work the same way.⁶

How much practice is enough isn't known. Across 12 trials of breathwork for stress, there was no clear link between total practice time and how much stress fell, partly because few studies recorded how much people really practised.²

Is it safe? When sighing becomes a problem

For healthy adults, breathwork looks low risk. The meta-analysis found no adverse events directly blamed on breathing exercises, although only a few trials looked for them. In the Stanford trial, 90% of participants described their experience as positive and 10% reported a negative one.^2,1

More sighing isn't always better. Sighing far more often than normal is linked to over-breathing that lowers carbon dioxide in the blood, which can bring symptoms of its own. In lab studies, people with panic disorder sighed more than others at rest, though daily-life studies haven't confirmed that, and one breathing therapy for panic disorder asks people to avoid sighs.⁶

Fast breathing styles have more reported side effects. In one trial of fast-paced breathwork in people with depression, a small group had hot flushes, shortness of breath or sweating.²

What to do with this

To try it: breathe in slowly through your nose, add a second short inhale to fill your lungs, then breathe out slowly and fully. Repeat for 5 minutes.¹
Make it a daily habit rather than an emergency trick: in the trial, the mood benefit grew with the number of days people had practised.¹
If you prefer box breathing or meditation, they lowered anxiety about as much per session. Pick the one you will actually keep doing.¹
Keep the pace slow and the exhale long: slow breathing techniques have the strongest evidence for lowering stress.^2,4
Don't turn it into sighing all day. Very frequent sighing is linked to over-breathing; stop if you feel dizzy or short of breath.⁶

How sure is this?

The main evidence is one trial: 108 adults without serious health conditions, most of them from one Stanford undergraduate class, with 30 in the cyclic sighing group. It was planned as an exploratory study, registered only after it ran, carried out remotely, and lasted just 4 weeks with no follow-up.¹
Mood and anxiety were self-reported, and practice was tracked only through daily surveys. In the breathwork meta-analysis, 9 of the 12 stress trials had some risk-of-bias concerns and 3 had a high risk of bias.^1,2
Much of what is known about natural sighs comes from animal and brain-tissue studies, and the review authors call the psychological 'reset' role of sighs a hypothesis that still needs evidence.^5,6
For the cadet trial we could read only the abstract, so we use only its main results, and we could not check its funding or conflict-of-interest statements.³
Industry ties: Andrew Huberman, a senior author of the Stanford trial, became an advisor to WHOOP, the maker of the wrist strap used, in June 2022. WHOOP donated the straps and participants kept them, though the company was not involved in the design or analysis. The first author of the breathwork meta-analysis trained as a breath teacher with the Breath-Body-Mind Foundation, and the slow-breathing review acknowledges support from a yoga association.^1,2,4

Common questions

What is a physiological sigh?

A breathing pattern that copies a natural sigh: a deep inhale through the nose, a second short inhale on top, then a long, slow exhale. Repeated for several minutes, it is called cyclic sighing.¹

How many physiological sighs should you do?

The trial that tested it used 5 minutes once a day for a month. No study has tested one or two sighs as a dose, and in lab studies a deep breath on command didn't show the relief effect of a natural sigh.^1,6

Is the physiological sigh backed by science?

Partly. One randomised trial of 108 adults found 5 minutes a day improved mood more than meditation and lowered breathing rate, and across 12 trials breathwork lowered stress by a small-to-medium amount. Larger trials registered in advance are still missing.^1,2

Physiological sigh vs box breathing: which is better?

Neither clearly. Both lowered anxiety by about the same amount per session in the Stanford trial, and both sped up the recovery of heart rate variability after hard exercise in cadets. Only cyclic sighing lifted positive mood significantly more than meditation.^1,3

Does the physiological sigh help you sleep?

It hasn't been shown to. In the Stanford trial, a month of daily cyclic sighing didn't change hours of sleep, sleep efficiency or daytime sleepiness.¹

Is sighing a lot a bad sign?

It can be. Very frequent sighing is linked to over-breathing and is seen more often in some anxiety and breathing problems. If you sigh constantly or often feel short of breath, see a doctor.⁶

Sources

Balban MY, Neri E, Kogon MM, Weed L, Nouriani B, Jo B, Holl G, Zeitzer JM, Spiegel D, Huberman AD. Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine, 2023. Randomised trial. doi.org/10.1016/j.xcrm.2022.100895
Fincham GW, Strauss C, Montero-Marin J, Cavanagh K. Effect of breathwork on stress and mental health: A meta-analysis of randomised-controlled trials. Scientific Reports, 2023. Meta-analysis. doi.org/10.1038/s41598-022-27247-y
Jones ME, Smith G, Acevedo A, Melton B. Effectiveness of Structured Breathwork Interventions on Heart Rate Variability and Heart Rate Recovery Following Maximal Exertion in Tactical Athletes. Medicine and Science in Sports and Exercise, 2026. Randomised trial. doi.org/10.1249/mss.0000000000003972
Zaccaro A, Piarulli A, Laurino M, Garbella E, Menicucci D, Neri B, Gemignani A. How Breath-Control Can Change Your Life: A Systematic Review on Psycho-Physiological Correlates of Slow Breathing. Frontiers in Human Neuroscience, 2018. Review. doi.org/10.3389/fnhum.2018.00353
Severs LJ, Vlemincx E, Ramirez JM. The psychophysiology of the sigh: I: The sigh from the physiological perspective. Biological Psychology, 2022. Review. doi.org/10.1016/j.biopsycho.2022.108313
Vlemincx E, Severs L, Ramirez JM. The psychophysiology of the sigh: II: The sigh from the psychological perspective. Biological Psychology, 2022. Review. doi.org/10.1016/j.biopsycho.2022.108386

The Breathwork Protocol gives you five breathwork techniques step by step, including cyclic sighing, a CO2 tolerance test and training, and vagus nerve exercises. The HRV & Stress Protocol adds an HRV measuring routine, cyclic sighing and resonance breathing, and a 4-week stress plan. Breathwork Protocol · HRV & Stress Protocol