Many practitioners think that the combination of stretching, balance, meditation and breathing signal the brain to release calming chemicals that lead to relaxation and decreased anxiety
There are two studies that look at how 60 minutes of yoga can affect your brain chemistry and subsequently your mood. One study compared yoga to reading and found a 27% increase in a chemical called GABA and the other study compared yoga to walking and found a 13% increase in GABA in subjects that had never done yoga before. In the second experiment there was also a significant improvement in mood and anxiety. GABA is a neurotransmitter that calms the brain and antidepressants medications work to increase this chemical. So why not try yoga instead!
Streeter CC, Jensen JE, Perlmutter RM, et al. Yoga Asana sessions increase brain GABA levels: a pilot study. J Altern Complement Med. 2007;13:419-426.
Streeter CC, Whitfield TH, Owen L, et al. Effects of Yoga Versus Walking on Mood, Anxiety, and Brain GABA Levels: A Randomized Controlled MRS Study. Journal of Alternative and Complementary Medicine. 2010;16(11):1145-1152. doi:10.1089/acm.2010.0007.