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.