Yoga May Help Treat Depression, Anxiety Disorders

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According to Streeter, "this all gives us one of the mechanisms by which yoga may be having a beneficial effect. There could be other mechanisms."

But another expert pointed to what he considered flaws in the research.

Zindel Segal, chairman of psychotherapy and a professor of psychology and psychiatry at the University of Toronto, has for years studied the use of behavioral interventions to alleviate psychological woes.

He said the Boston researchers were to be commended for using brain scan imaging technologies to investigate the effectiveness of these techniques. But he questioned why the yoga group was simply compared to a sedentary reading group and not to another movement-based group.

"Exercise itself may have some effects on GABA, so I think in this study, you'd really want that comparison," he said. Including such a control group would make it clear that it was yoga and not just an hour of physical exertion that was responsible for the brain changes.

He also pointed out that all of the people in the study were mentally healthy, and clinical depression and anxiety disorders involve more than the "daily fluctuations in stress and tension" that healthy individuals are prone to.

"We know that yoga can have a profound effect" on smoothing out life's daily ups and downs, Segal said. "But so does working out on a Stairmaster for an hour."

Segal also questioned the role of GABA in depression. While it may play a role in anxiety disorders, "GABA is not one of the main neurotransmitters that seems to be a part of the depression story," he said. Other neurochemicals -- most notably serotonin -- play much bigger roles in the disorder, he said.

None of this means that the study's findings are without merit, Segal said. "In fact," he said, "we have a program called 'mindfulness-based cognitive therapy,' where we do use yoga, as well as mindfulness meditation," as therapeutic tools. Streeter's findings "suggest the need for more study of these practices," he said.

Streeter agreed that her study is probably just a beginning.