SIGH. It's good for you.
A study recently published in the journal Cell (1) reviewed the impact of three daily, 5-minute controlled breathing practices: physiological sighing, box breathing and cyclic hyperventilation and mindful meditation, where no breathing techniques were used. The outcomes measured were mood (positive and negative affect), anxiety and respiratory and heart rates.
Over a 28-day period all four groups showed significant improvement in positive affect and a reduction in anxiety and negative affect. Basically all participants felt better and less anxious. Cyclic sighing, in particular, was most effective at increasing positive affect.
How do you do a "cyclic sigh?" Breathe in through your nose (count of 1.00). When you've comfortably filled your lungs, take a second, shorter, deeper breath in (count of 0.25), also through your nose. Then exhale fully through your mouth (count of 2.00). The exhale is longer than the total of the two inhales.
I found a YouTube video that guides the 5-minute cyclic breathing practice if you want to try this study on yourself :). Side note: Neuroscientist Dr. Andrew Huberman is one of the authors of the study. I enjoy his Huberman Lab podcast and newsletter and recommend it if you want way too much information on lots of aspects of health.
Wishing you health and ease (sigh…),