Why breathing out slowly calms you down

"Take a deep breath" is the most common advice given to anxious people, and it is only half right. The calming part of a breath is mostly on the way out.

Your heart changes speed with every breath

Put two fingers on your pulse and breathe slowly. You may notice your heart speeding up a little as you breathe in and slowing a little as you breathe out. This is normal and healthy. It's called respiratory sinus arrhythmia.

The slowing on the exhale is carried by the vagus nerve, the main nerve of the parasympathetic nervous system, which is responsible for rest, digestion and recovery. On each out-breath, it applies a gentle brake to the heart.

Longer out means more time with the brake on

If you make your exhale longer than your inhale, you spend a larger share of every minute in that slowing phase. Breathing slowly overall, at around five or six breaths a minute, also increases heart rate variability, a marker of how flexibly the nervous system adapts, which is generally associated with better emotional regulation (Lehrer & Gevirtz, 2014).

Studies of slow breathing consistently find increased parasympathetic activity, and people commonly report feeling calmer and less anxious (Zaccaro et al., 2018). Some of these changes show up after a single session (Magnon et al., 2021).

Why "deep breaths" can backfire

When people are told to breathe deeply, they often take big, fast breaths in. That can lower carbon dioxide in the blood and cause tingling, dizziness and a feeling of not getting enough air, which feels like more anxiety. Slow and soft works better than big.

Try it

In for four, rest for two, out for six. That's the extended exhale, and it's what Calmalo guides you through when your heart is racing. The circle grows as you breathe in and softens, slowly, as you breathe out.