Picture a breath with two inhales and one long, slow exhale, the kind a child makes after a long cry or a sleeper makes in deep rest, repeated for five minutes a day. In a 2023 Stanford trial, that simple pattern produced the largest gain in positive mood over a beginner's meditation practice and the deepest drop in resting breathing rate of any group tested [1].
Run by a team led by David Spiegel and Andrew Huberman, the trial randomized 108 healthy adults to one of four daily five-minute practices for 28 days: cyclic sighing, box breathing, cyclic hyperventilation with breath retention, or mindfulness meditation [1][2]. The sighing group gained about 1.91 points per day on the positive-affect subscale of the PANAS mood questionnaire, roughly a third more than the meditation group's 1.22 [1].
What the trial actually tested
The study was small, online, and deliberately low-tech. Of 134 randomized, 108 completed after attrition; final group sizes were 30 in cyclic sighing, 21 in box breathing, 33 in cyclic hyperventilation with retention, and 24 in mindfulness meditation [2]. Each day, participants watched a short pre-recorded video of Huberman instructing them in their technique, then completed a five-minute practice and brief questionnaires on state anxiety, mood, and sleep [1][2]. Run during the pandemic, the trial used a WHOOP Strap 2.0 wrist sensor to track daily resting respiratory rate and heart-rate variability.
On the headline mood and anxiety measures, all three controlled-breathing groups improved more than the meditation group; on the secondary outcome of resting respiratory rate, only the cyclic sighing group significantly outperformed meditation [1][3]. In the sighing group, the slower the breathing got, the larger the mood lift, with the two clearly linked [3].
The physiology of a sigh
In respiratory physiology, a sigh is a specific event. Roughly every few minutes, healthy lungs spontaneously inflate more deeply than a normal breath, then exhale fully, reinflating small airways and alveoli that collapse during quiet tidal breathing [1][4]. Cyclic sighing borrows that reflex on purpose.
A full cycle has three parts: a deep inhale through the nose; a short second sip that pushes the lungs to maximum volume, reopening collapsed alveoli; and a slow, extended exhale through the mouth, often twice as long as the inhale [2]. Each cycle is unhurried and the technique needs no equipment, counting, or app [2].
The double inhale is what distinguishes cyclic sighing from most other breathwork. The second sip recruits alveoli closed during the first breath, putting more gas-exchange surface online for the slow exhale [1]. Long exhales also recruit the vagus nerve, linking brainstem to heart and gut; a longer exhale raises average vagal tone, showing up as more variable heart rate and a sense of calm [1].
How it differs from other breathing practices
Box breathing, popularized by military and first-responder programs, uses four equal phases, often four seconds of inhale, hold, exhale, and hold [2][5]. Its protocol is symmetrical and predictable, useful in high-stress settings where the goal is steady regulation. By design, it minimizes the very thing cyclic sighing amplifies: the difference between the two halves of the breath, the asymmetry that drives the vagal pathway.
Cyclic hyperventilation with retention is the opposite end of the spectrum. Rapid, forceful breathing drops blood CO2, followed by a long breath-hold on empty lungs. This group also improved more than meditation on most measures, but the technique carries notable hyperventilation risk if performed too vigorously [1][6]. Cyclic sighing is, by contrast, what the researchers call the simplest of the three breathwork protocols: no holds, no instructions about how hard to push, and a pace set by a slow exhale [2][4]. A beginner can be off and running in a single cycle.
The mindfulness control asked participants to focus on the sensation of breath at the forehead for five minutes a day [4]. The authors note this does not mean meditation is useless; the comparison group practiced only five minutes a day, and meditation's documented benefits tend to grow with longer practice. For a beginner trying to feel different in 30 days, structured exhalation appears to do more than a beginner's dose of focused attention.
The honest limits of the evidence
The design sets real boundaries on what the trial can claim. Adherence was monitored by questionnaire and the WHOOP strap, but no one checked technique in real time, and the population was a self-selected group of healthy adults [1][2]. People with moderate to severe psychiatric conditions were excluded, so the result cannot be assumed to generalize to clinical anxiety or depression [2].
The outcomes were self-reported mood and anxiety questionnaires, and the only physiological signals were resting respiratory rate, heart rate, and heart-rate variability from a wrist sensor. Heart rate did not change, and the authors did not collect blood biomarkers of stress or brain imaging during the practice [1][2]. A follow-up trial of an estimated 80 participants is registered to add fMRI and longer physiological readouts [5]. The proposed mechanism, increased vagal tone during slow exhalation, has its roots in a 2018 review of exhale-emphasized breathwork [7].
Effect sizes are modest. A 1.91-point daily improvement on the PANAS positive-affect subscale, which runs from 10 to 50, is meaningful at the group level, but standard deviations were large enough that any individual participant's experience could easily be a wash [1][3]. Longer-term effects are unknown; the trial ran 28 days [5].
A practical how-to and a safety note
Cyclic sighing is slower and more controlled than a hyperventilation practice: the inhale is not forceful, there is no breath-hold, and the pace is set by a slow exhale. The Cambridge University Hospitals NHS Foundation Trust warns, in a standard patient information leaflet on breathing exercises, that continuous over-breathing lowers blood CO2, with symptoms that can include tingling, dizziness, headaches, muscle cramps, and a sense of unreality [6]. The same caution applies to cyclic sighing if the pace is too fast or the breaths too deep, particularly for people with cardiovascular or respiratory conditions. Stop any breathing exercise that causes pain and seek advice from a GP if symptoms persist [6]. This is general information, not medical advice. If you have a cardiovascular, respiratory, or psychiatric condition, or are pregnant, consult a GP or qualified health professional before starting any breathwork practice.
Inhale slowly through the nose, deep into the belly, until your lungs feel comfortably full. Take a short second sip of air through the nose, as if finishing a glass. Exhale slowly through the mouth, longer than the inhale, until your lungs feel empty. Pause, and repeat for five minutes.
The Stanford finding is not that breathing beats meditation, full stop. It is that a specific, exhale-emphasized, double-inhale pattern, practiced in five minutes a day for a month, can move the needle on mood and breathing rate more than a beginner's meditation practice of the same dose [8]. For a healthy adult, the cyclic sigh is a reasonable short-term experiment, with the caveat that a single 28-day RCT is not yet a long-term evidence base.