Yoga, the 5,000-year-old Indian practice, has positive effects on mild depression and sleep complaints, even in the absence of drug treatments, and improves symptoms associated with schizophrenia and ADHD in patients on medication, according to a systematic review of the exercise on major clinical psychiatric disorders.

The review of more than one hundred studies focusing on 16 high-quality controlled studies looked at the effects of yoga on depression, schizophrenia, ADHD, sleep complaints, eating disorders and cognition problems.

Benefits of the exercise were found for all mental health illnesses included in the review, except for eating disorders and cognition problems as the evidence for these was conflicting or lacking.

Dr. P. Murali Doraiswamy, a professor of psychiatry and medicine at Duke University Medical Center, US, and author of the study, explained that the emerging scientific evidence in support of yoga on psychiatric disorders is “highly promising” and showed that yoga may not only help to improve symptoms, but also may have an ancillary role in the prevention of stress-related mental illnesses.

The review found evidence from biomarker studies showing that yoga influences key elements of the human body thought to play a role in mental health in similar ways to that of antidepressants and psychotherapy. One study found that the exercise affects neurotransmitters, inflammation, oxidative stress, lipids, growth factors and second messengers.

While there has been an increase in the number of medications available for mental health disorders, many of which can be life saving for patients, there remains “a considerable unmet need,” according to Dr. Meera Balasubramaniam, lead author of the study, who is also based at Duke University, US.

Poor compliance and relapse as well as treatment resistance are growing problems, and medications are expensive and can leave patients with significant side effects.

“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 Doraiswamy.

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

There are many benefits associated with practicing yoga for improving mental health, including, fewer side effects, relatively low cost, generally good access and the improvement of physical fitness, the researchers added.

The review has been published in the open-access journal, Frontiers in Psychiatry.