Randomized controlled trial of bikram yoga and aerobic exercise for depression in women: Efficacy and stress-based mechanisms

•Bikram yoga and aerobic exercise led to greater depression response than a wait-list condition.•Bikram yoga and aerobic exercise led to decreased levels of rumination.•Decreases in rumination drove the symptom change seen in Bikram yoga and exercise.•Increases in mindful acceptance drove the symptom change seen in aerobic exercise. The current study presents a randomized controlled 8-week trial of Bikram yoga, aerobic exercise, and waitlist for depression. Bikram yoga was chosen specifically for its standardized nature. Further, we examined changes in three stress-related constructs—perceived stress, rumination, and mindfulness—as mediators of antidepressant effects. Fifty-three women (age 18–65; 74% White) with a unipolar depressive disorder were randomly assigned to one of the three conditions. Response was defined as >50% reduction on the Hamilton Rating Scale for Depression (HAM-D). Remission was defined as no longer meeting criteria for depression and a HAM-D ≤ 7. Self-reported perceived stress, rumination, and mindfulness were assessed weekly. In the intention-to-treat sample (n = 53), response rates were significantly higher in the Bikram yoga (61.1%; χ2 = 10.48, p = .001) and aerobic exercise (60.0%; χ2 = 10.44, p = .001) conditions relative to waitlist (6.7%). In the completer sample (n = 42), 73.3% (χ2 = 11.41, p = .001) of women in yoga and 80.0% (χ2 = 13.72, p < .001) in exercise achieved response compared to 8.3% in waitlist. Reductions in rumination significantly mediated HAM-D change for both active treatments, and mindful acceptance was a partial mediator in the exercise condition. The sample was small in size, consisted of women only, and was ethnically homogenous. Inter-rater reliability was not assessed, aerobic exercise was not standardized, and mediators were assessed by self-report. Bikram yoga showed descriptively similar efficacy to aerobic exercise and both may work, in part, by helping individuals interrupt negative thinking.