Slow Breathing

Why a longer out-breath calms your body

What happens in your body when you slow your breathing down, why the breath out matters most, and how to try it in a few minutes

Written by Ivana, psychologist and psychotherapist

8 minute read  ·  1,726 words

You’re about to walk into a difficult conversation. Your heart’s going faster than it needs to, your shoulders have crept up toward your ears, and your breathing has turned quick and shallow without you deciding anything of the sort. Most of what’s happening in your body right then is automatic. You can’t tell your heart to slow down and expect it to listen.

Your breathing is different. It runs on its own all day and all night, but it’s also the one part of this system you can take over on purpose, at any moment, with no equipment at all. And when you slow it down, other parts of the system tend to follow.

That’s the idea behind slow breathing. It’s simple, it’s free, and it’s been studied more than most calming techniques: one review alone gathered over two hundred studies.

Your heart listens to your breath

Even at rest, your heart doesn’t beat like a metronome. When you breathe in, it speeds up a little. When you breathe out, it slows down again. This rise and fall is called respiratory sinus arrhythmia, and despite the name, it’s a normal, healthy pattern. It’s one of the ways the vagus nerve, a major nerve connecting the brain with the heart and other organs, adjusts the heart from moment to moment.

The variation from one heartbeat to the next is called heart rate variability. In general, more variability at rest is a sign of a flexible nervous system, one that can rise to a demand and then settle again.

Slowing down makes the waves bigger

In research, slow breathing usually means fewer than ten breaths a minute, and often around six. At that pace, the heart’s rise and fall with each breath gets much bigger. A review of fifteen studies found that slow breathing increased heart rate variability, alongside changes in brain activity and reports of feeling more relaxed and less anxious.

The biggest review, pooling 223 studies, found that the part of heart rate variability that is used to track the vagus nerve went up during slow breathing, straight after a single session, and after weeks of regular practice. The authors called slow breathing a low-cost technique with few side effects expected.

There’s a sweet spot, too. For most adults, the heart’s swings are biggest at around five and a half to six breaths a minute, and going slower than that doesn’t add more. Researchers call it the resonance pace, and it differs a little from person to person.

Six breaths a minute is an old rhythm

In 2001, researchers asked 23 healthy adults to recite the rosary in Latin, or a yoga mantra, while their breathing and circulation were measured. Both recitations happened to slow breathing to about six breaths a minute, and both produced strong, synchronized waves in heart rhythm and blood pressure. The researchers suggested that part of what people have long found calming in these practices may be the breathing rhythm built into them.

The exhale is the calming half

Because the heart slows on the breath out, it makes sense to ask whether the out-breath matters more than the pace. Researchers in Belgium asked 30 people to breathe in four patterns: slow or ordinary pace, with either a long out-breath or a long in-breath. Breathing out for longer than they breathed in helped people feel more relaxed, at either pace. The slower pace on its own mostly gave people a little more energy. Slow breathing with a long out-breath gave the clearest calming signal in the heart.

A few minutes a day

In 2023, a team at Stanford compared three breathing exercises with mindfulness meditationmindfulness meditationPractice in paying attention to the present moment, such as the breath or sounds, and letting thoughts come and go without following them.. For a month, people spent five minutes a day on their assigned practice. One group did cyclic sighing: a breath in through the nose, a second short breath in to top up the lungs, then a long, slow breath out through the mouth. Another did box breathing, with equal counts for breathing in, holding, breathing out and holding. A third breathed fast, with long in-breaths, and then held their breath.

Everyone felt less anxious, meditators included. But cyclic sighing, the practice built around a long out-breath, gave the biggest lift in good mood and the biggest drop in breathing rate. It was a small first study that wasn’t registered in advance, so it’s a promising start.

What the trials add up to

When a meta-analysismeta-analysisA study of studies: it pools the results of many experiments on the same question to estimate how large an effect usually is, rather than relying on any single result. pooled the randomized controlled trialsrandomized controlled trialsStudies in which people are assigned to groups by chance, so that differences between the groups at the end can more fairly be put down to the practice being tested. of breathing practices, people who practiced felt less stressed than people who didn’t, a modest but real difference, and they were less anxious and low by about the same amount.

Most of the trials had some risk of biasrisk of biasHow likely it is that the way a study was run tilted its results, for example because people knew which practice was expected to work, or because many dropped out., so the results are encouraging rather than settled, and the authors warned against letting the hype run ahead of the evidence.

There’s also a more structured version, called heart rate variability biofeedback, where people practice breathing at their own resonance pace while watching their heart rhythm on a screen. A review of 24 studies found a large drop in self-reported stress and anxiety, while noting that more well-controlled studies are needed. A larger review from 2020, of 58 randomized trials, found a smaller effect, about the same as other treatments that work, with some of the biggest changes in anxiety, low mood and anger.

Start with four in and six out

Breathe in gently through your nose for a count of about four, and out through your nose or softly parted lips for a count of about six. That comes to six breaths a minute. The counts don’t need to be exact. What matters is that the breath is slow, and that the out-breath is longer than the in-breath. If four in and six out leaves you hungry for air, try three in and five out instead.

Slow, not deep

Slow breathing isn’t the same as taking big breaths. Slower breaths are naturally a little fuller, but if you breathe very deeply as well as slowly, you can blow off too much carbon dioxide and start to feel lightheaded or tingly, which is the opposite of what you want (ask anyone who’s blown up a lot of balloons for a party). Keep each breath comfortable, as if you were breathing a little more slowly than usual rather than filling your lungs to the top. If you do feel lightheaded, make the breaths smaller.

When to stop, and when to ask

Some people find that paying close attention to their breathing makes them more anxious at first, especially if they’ve had panic attacks or have been through trauma. If that happens, it can help to keep your eyes open, count more loosely, or focus on the out-breath only. If it still makes things worse, it’s fine to set it aside.

If you live with panic attacks, go gently. Very big breaths can bring on the dizziness you’re trying to avoid, and slow breathing works best as everyday practice, not as an emergency exit. For panic disorder itself, the evidence for breathing training is mixed.

If you tend to feel faint when you stand up, practice sitting or lying down at first, and stop if you feel woozy. If you have a heart or lung condition, or you’ve been told to be careful with breathing exercises, check with your doctor first, and skip the holds in box breathing.

Try it most days, and when you’re calm

Five minutes is a good place to start, most days, for a few weeks. Reviews of breathing programs suggest that regular sessions of at least five minutes do more than the odd quick one. It also helps to practice when nothing in particular is wrong, so the pattern is already familiar by the time you need it. A slow out-breath in the corridor before a difficult meeting comes more easily if you’ve already done it a few times at the kitchen table.

In a tight moment, two or three slow sighs may take the edge off: two breaths in through the nose, the second one topping up the first, then one long, unhurried breath out. The study tested five minutes a day, though, so think of a quick sigh as a taster.

Breathe in, and take a little longer on the way out.