The review, which examined results from 16 well-designed studies of yoga’s effect on mental illness, concluded that yogamay have positive effects for people with depression and sleep complaints even if they don’t take medication, as well as for people suffering from schizophrenia and ADHD who are taking medication.

Studies that have looked at yoga suggest the practice influences chemical messengers in the brain, inflammation in the body, and other biological factors in much the same way antidepressants and psychotherapy do, said study researcher Dr. P. Murali Doraiswamy, a professor of psychiatry and medicine at Duke University Medical Center in. [See The Science of Yoga and Why It Works.]

In one study of 69 older adults with mild depression, weekly yoga sessions reduced depression scores by 40 percent at six months. A comparison group of adults who didn’t take yoga, and a group that practiced a form of complementary medicine called Ayurveda, did not show changes in depression scores.

In another study of 39 adults who were sleeping poorly (they were receiving chemotherapy), seven weeks of yoga improved sleep quality and reduced the need for sleep aids. People who did not take the yoga sessions (control group) did not have an improvement in sleep.