New evidence bolsters the belief that yoga can offer real and lasting relief to people with depression.
Dr. Chris Streeter, a psychiatrist at Boston University's School of Medicine, said the new study she led builds on earlier work showing a correlation between yoga and levels of GABA (gamma aminobutyric acid), a chemical in the brain. Yoga seems to raise GABA levels, much as anti-depression and anti-anxiety drugs do, she explained.
The effect was seen four days after performing yoga, but not eight days later, suggesting yoga should be done regularly to counter depression, Streeter said.
"Once depressive symptoms improve, twice a week is probably better," she said.
The study focused on Iyengar yoga, a variety that emphasizes holding poses precisely for long periods, and controlled breathing. But any type of yoga would likely give similar results, Streeter said.
"A downward dog is a downward dog," she said, referring to a common yoga pose.
The 12-week study followed 30 adults with depression. All but two were not taking antidepressants. The subjects were divided into two groups: One underwent three 90-minute yoga classes and four 30-minute "homework" sessions each week (researchers called this group "high-dose"); the other did two 90-minute classes and three 30-minute homework sessions a week ("low-dose").
Over the course of the study, the high-dose group spent 123 hours in sessions while the low-dose group spent 87 hours in sessions.
According to the paper, there was no control group because researchers were trying to determine dosing levels, so a no-dose group wasn't needed.
The researchers reported both groups saw improvement in symptoms, including more feelings of positivity and calm and less physical exhaustion, depression and anxiety. The amount of improvement correlated with the total time spent on yoga and breathing exercises, but the differences between the two groups weren't large enough to be considered significant, Streeter said.
This may have been due to the small number of study participants, and larger studies are needed to confirm the finding, the researchers concluded. Also, the study could not prove cause and effect.
Previous research has shown that exercise can aid people with depression, but Streeter said yoga may be more helpful to people with depression than other common types of exercise.
"Exercise is good for people," she said. "I thing yoga has a different quality."
The study was published in the November issue of the Journal of Psychiatric Practice.
"What makes yoga different is a very specific mind component," said Dr. Gregory Brown, psychiatrist, yoga instructor and founder of the Center for Green Psychiatry in West Lake Hills, Texas.
His clinic uses yoga as a supplement -- not a replacement for -- traditional treatment of medication and therapy for depression, anxiety and PTSD (post-traumatic stress disorder). Brown wasn't involved with the new study.
"We do a lot of breath work," he said. "It really helps with anxiety."
Brown said the small size of the study doesn't cancel its findings.
"A lot of skeptics focus on the limitations," he said. "I'd focus on how to broaden this kind of research."
Brown said yoga can be an attractive option to people with depression who wish to boost their efforts to combat symptoms or don't want to take medications.
"Any tool that we can add to our toolkit" is worthwhile, Brown said.
Streeter also said yoga may help people already being treated with antidepressants. Two of the participants added to the study were on medication and their symptoms improved with yoga, she said.
"A lot of people get put on Prozac by their PCP [primary care practitioner]," she said. "They're on antidepressants and they're still depressed."
Visit the U.S. National Center for Complementary and Integrative Health for more on yoga.