Yoga has gained such momentum in the U.S. in recent years that it’s hard not to pass a yoga studio on your daily commute or read of some new research study touting the health benefits of the 5,000-year old practice. Researchers behind a new study wondered "whether the evidence matched the promise" when it comes to yoga's ability to improve the symptoms of psychiatric disorders like stress, depression and ADHD.

Previous evidence has suggested that yoga might have an effect on mental health by influencing levels of neurotransmitters in the brain, increasing bone-derived neurotrophic factor (BDNF), and reducing activity in the hypothalamic-pituitary-adrenal (HPA) axis, which governs the stress response. But different studies have arrived at different results, and there’s been no comprehensive review to analyze the yoga-mental health relationship.

If the promise of yoga on mental health was found in a drug, it would be the best selling medication world-wide.

To address this rather large question, the team reviewed a number of previous studies that looked at the connection between various mental health disorders and yoga. To be included in the review, the previous research had to be randomized controlled trials (RCTs), which are more rigorous and objective than studies using other methods, like correlations or observations. After the weeding-out process, 16 studies made the cut. They focused on the effect of various subtypes of yoga on psychiatric disorders like depression, schizophrenia, ADHD, sleep problems, cognitive problems, and eating disorders.

Interestingly, the authors found that yoga was linked to improvement in all of the disorders investigated except for eating disorders and cognitive problems. They highlight the fact that yoga appears to provide an "acute benefit" for depression, and could provide an important adjunct to medication in the treatment of schizophrenia and ADHD. The authors say that the results are especially exciting since recent studies have found antidepressants to be of relatively low effectiveness.

"The search for improved treatments, including non-drug based, to meet the holistic needs of patients is of paramount importance and we call for more research into yoga as a global priority," said study author P. Murali Doraiswamy in a news release. "If the promise of yoga on mental health was found in a drug, it would be the best selling medication world-wide."

Hopefully, this review will be of use to mental health practitioners who may not be sure how to respond to questions about the benefits of yoga. As the authors say, "yoga has become such a cultural phenomenon that it has become difficult for physicians and patients to differentiate legitimate claims from hype." This study should help address that concern, at least in part. But the authors also urge that additional research be carried out, both to replicate the work done here and to address the same questions using additional methods like biochemical tests and brain imaging.

The study was carried out by a team at Duke University, and published in Frontiers in Psychiatry.