There's growing evidence that breathing is linked to brain activity in interesting ways [1]. There's also the "4-7-8" breathing technique that is supposed to help you fall asleep faster. [2] On top of that, concentrating on breathing takes your focus away from other inner monologue and intrusive thoughts; meditation programs typically start you off on that path. [1] https://news.northwestern.edu/stories/2016/12/rhyth…
Resonant breathing biofeedback training for stress reduction among manufacturing operators https://www.ncbi.nlm.nih.gov/pubmed/23294659
Effect of Fast and Slow Pranayama Practice on Cognitive Functions In Healthy Volunteers https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3939514/
Both citations from https://www.reddit.com/r/Nootropics/comments/25kfkf/breath_o...