“A longer exhale helps by increasing the activation of the body’s parasympathetic nervous system, which counteracts stress hormones, lowers heart rate, and reduces overall physiological stress,” she says.

Source: https://www.independent.co.uk/life-style/health-and-families/people-anxiety-author-anxiety-uk-b2426990.html

When we take a slow, deep breaths, we signal to our parasympathetic nervous system to calm down and restore our emotional and mental state.

Source: https://www.dailymail.co.uk/femail/health/article-11879897/Simple-exercise-resets-nervous-quickly-relives-beaches-migraines-neck-pain.html?ns_mchannel=rss&ns_campaign=1490&ito=1490