(NBC News) When you step out of a yoga class, no doubt you feel better from head to toe. Your muscles feel more relaxed, you may feel stronger, and then there’s the mental clarity only om-ing can bring. But what’s really going on in your brain when you pop in and out of downward-facing dog? “We know that accumulating evidence shows yoga is good for your body, health and mind. Yoga has been used in the treatment of anxiety conditions, depression, insomnia, eating disorders, and others,” says Jonathan Greenberg, PhD, a postdoctoral research fellow in the department of psychiatry at Massachusetts General Hospital and Harvard Medical School...