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Illustrated · 20+ peer-reviewed studies

How breathing affects your body and mind

Breathing runs on autopilot, but it's also the one part of your automatic nervous system you can steer on purpose. Change how you breathe and you change your heart rhythm, your blood-pressure reflexes and, for many people, how calm or alert they feel. Here's what the research shows, and how sure we can be.

Try six slow breaths

Your breath steers your nervous system

Your autonomic nervous system has two broad modes: the sympathetic "fight or flight" side, which speeds things up, and the parasympathetic "rest and digest" side. Its main nerve is the vagus nerve, which slows things down. You can't simply decide to lower your heart rate, but you can decide to breathe slowly with a long exhale. That's a lever into the same system.

  1. A longer exhaleMore vagal (calming) signal to the heartHeart beats a little slower
  2. About six breaths a minuteThe baroreflex swings more stronglyBlood pressure held steadier
  3. Your breathing rhythmWired to the brain’s arousal centre (shown in mice)Calmer or more alert state
Three routes from breathing to body and mind. The first two are measured in humans; the third, the wiring between the breathing rhythm and the arousal centre, has so far been shown in mice.

The link runs deep. In mice, a small group of neurons in the brain's breathing rhythm generator connects straight to the arousal centre (the locus coeruleus). When researchers removed these neurons, breathing stayed normal but the mice became noticeably calmer. Recordings from inside the human brain show that breathing through the nose sets a rhythm in emotion- and memory-related areas. In the same study, people recognised fearful faces and recalled memories better during an in-breath.

Your heart follows your breath

Your heart speeds up a little each time you breathe in and slows each time you breathe out. This is completely normal, it's called respiratory sinus arrhythmia, and doctors use it as a sign of healthy vagal activity. It may help your lungs and blood flow work together more efficiently.

Heart rate rises on the in-breath and falls on the out-breathTwo stacked panels over 20 seconds of breathing 4 seconds in and 6 seconds out. The top panel shows lung volume rising and falling. The bottom panel shows heart rate following the same wave a moment later: up during each inhale, down during each exhale. Breath Lung volume: up for 4 s, down for 6 s Heart rate Heart rate: a little faster on each inhale, slower on each exhale in out in out full empty faster slower

Breath (lung volume)Heart rate

Breathing 4 seconds in and 6 seconds out: heart rate climbs during each inhale (shaded green) and falls during each longer exhale (shaded violet).

That's why the exhale is the calming half. In an experiment with 30 people, making the out-breath longer than the in-breath helped them feel more relaxed and less stressed than simply breathing slowly. With slow breathing, it also boosted a vagal marker of heart-rate variability. Every pattern in Breathcharge except box breathing gives the exhale at least as much time as the inhale.

Slower breathing, calmer body

Breathing rates comparedA scale from 0 to 20 breaths per minute. Most adults breathe about 12 to 20 times a minute at rest. The Breathcharge techniques sit far lower: 4-7-8 at about 3.2, box breathing 3.8, coherent breathing 5.5, the calm 4-6 pattern 6, and the physiological sigh about 6.7 breaths per minute. typical at rest 12–20 / min 4-7-8: 3.2 breaths per minute 4-7-8 3.2 Box: 3.8 breaths per minute Box 3.8 Coherent 5.5: 5.5 breaths per minute Coherent 5.5 5.5 Calm 4·6: 6.0 breaths per minute Calm 4·6 6.0 Physiological sigh: 6.7 breaths per minute Physiological sigh 6.7 05101520 breaths per minute
Breathing rates on one scale. Ordinary resting breathing sits at about 12 to 20 breaths a minute; the techniques in Breathcharge run at 3 to 7.

Across the research, "slow breathing" usually means under 10 breaths a minute.

  • Heart-rate variability. A 2022 meta-analysis of 223 studies found that it reliably raises heart-rate variability, the beat-to-beat flexibility that reflects vagal ("rest-and-digest") activity. That held during practice, straight after one session, and after weeks of training.
  • How people feel. A systematic review linked slow breathing with feeling more relaxed, comfortable and alert, and with less anxiety, anger and low mood.
  • Lungs and reflexes. A review in the European Respiratory Society's journal describes how slow breathing makes each breath more efficient and changes the reflexes that steady blood pressure and respond to CO2.

Resonance: around six breaths a minute

Heart-rate swings are largest at around six breaths a minuteA schematic curve: the size of the heart-rate rise and fall with each breath is small at fast breathing rates, peaks at about 5.5 to 6 breaths per minute, and is smaller again at very slow rates. resonance Size of heart-rate swings by breathing rate (schematic) bigger smaller breaths per minute 2468101214
Schematic: the heart-rate swing with each breath is largest near 5.5 to 6 breaths a minute, where heart and breath rhythms reinforce each other. After Lehrer & Gevirtz (2014).

At about six breaths a minute, something special happens: heart rate and breathing fall into step and reinforce each other. This is resonance, and it's the basis of HRV biofeedback. It is thought to work by exercising the baroreflex, the reflex that keeps your blood pressure steady.

23 peoplereciting the rosary or a yoga mantra slowed to ~6 breaths/min, and their blood-pressure reflex grew stronger (BMJ, 2001)
149.7 → 141.1systolic mmHg while people with high blood pressure breathed at 6/min, without over-breathing (2005)
Calmer alarmbreathing at 6/min made the body's alarm response to rising CO2 and falling oxygen less reactive (2001)

These are short laboratory measurements during slow breathing, not long-term treatment results.

What it does for your mind

  • Stress, anxiety and mood. A 2023 meta-analysis of randomised trials (12 trials, 785 adults for stress) found that breathwork produced a small-to-moderate reduction in self-reported stress compared with control groups (Hedges' g = −0.35). Anxiety and low mood showed similar effects.
  • Cyclic sighing. In a month-long Stanford study, five minutes a day of cyclic sighing lifted positive mood more than mindfulness meditation did.
  • Sleep. In a 30-day trial, young adults who did 15 minutes of six-breaths-a-minute breathing in the evening reported better sleep than those who used social media instead.
  • Not over-breathing. In people with panic disorder, a small trial found that learning to breathe more slowly and gently, so as not to blow off too much CO2, reduced panic symptoms. That was a clinical therapy, not an app.

How strong is the evidence?

TechniqueBest evidence so farStrength
Slow / coherent breathingMeta-analyses of 200+ studies on heart-rate variability and 58 trials of resonance training. The largest placebo-controlled trial found no edge over a faster "placebo" breathing routine.Strongest
Physiological sighOne month-long randomised study of about 100 adults: better mood than mindfulness and a lower resting breathing rate.Promising, early
Box breathingImproved mood in the same study, but not significantly more than meditation. A 30-person lab study of the related "tactical breathing" showed lower arousal.Limited
4-7-8 breathingOne small before-and-after study: a few beats per minute lower heart rate right after. There was no comparison group.Very limited

The honest summary: slow breathing with a longer exhale reliably shifts your body towards calm while you do it. Regular practice gives small-to-moderate benefits for stress and mood. Some of that comes from simply taking a calm daily pause: in the largest placebo-controlled trial, a faster "placebo" breathing routine helped just as much. Most studies are short and involve healthy young adults. Higher heart-rate variability during slow breathing is a marker, not a cure.

Breathing safely

Short holds like those in box and 4-7-8 breathing are easy for the body: during any breath hold your brain keeps generating the breathing rhythm, and an automatic reflex makes you breathe again well before you could come to harm.

The slow patterns here are gentle, but holds and deep inhales can make you light-headed. Stop and breathe normally if you feel dizzy. Never practise breath holds in or near water, or while driving. If you are pregnant, or have a heart, lung or seizure condition or panic disorder, check with a clinician first. Breathing exercises can complement medical care but don't replace it.

Questions

Does slow breathing really calm you down?

Yes, in the short term. Slow breathing reliably increases heart-rate variability, a marker of the calming side of the nervous system, and meta-analyses of randomised trials show small-to-moderate reductions in self-reported stress and anxiety.

Why does a longer exhale relax you?

Your heart naturally slows during each out-breath and speeds up during each in-breath. Making the exhale longer than the inhale tips each breath towards slowing, and experiments show it feels more relaxing than slow breathing alone.

What is the best breathing rate to relax?

Around five to six breaths per minute is where heart and breath rhythms resonate for most adults. A calm, regular practice matters more than hitting an exact number.

Can breathing exercises lower blood pressure?

Breathing at about six breaths a minute temporarily lowered blood pressure in lab studies of people with high blood pressure. It can be a helpful habit but is not a substitute for medical treatment.

Which breathing technique has the most evidence?

Slow, paced breathing at about six breaths a minute (coherent or resonance breathing) has the deepest research base. The physiological sigh is promising but rests on fewer studies; box and 4-7-8 breathing have limited direct evidence.

Sources