Psychological Function, Iyengar Yoga, and Coherent Breathing: A Randomized Controlled Dosing Study.

Background: Evidence suggests that yoga may be an effective treatment for major depressive disorder (MDD). Studies evaluating the "dosing" of yoga treatment and efficacy for MDD are needed. The goal of this study was to assess the effects of an intervention combining Iyengar yoga and coherent breathing in participants with MDD and determine the optimal intervention dose. Methods: Thirty-two participants (18 to 65 y of age) diagnosed with MDD were randomized to a high-dose group (HDG) or a low-dose group (LDG) of yoga and coherent breathing for 12 weeks. The HDG (n=15) involved three 90-minute yoga classes and four 30-minute homework sessions per week. The LDG (n=15) involved two 90-minute yoga classes and three 30-minute homework sessions per week. Participants were evaluated at baseline, week 4, week 8, and week 12 with the following instruments: Positivity Self-Test, Spielberger State Anxiety Inventory, Patient Health Questionnaire-9, Pittsburgh Sleep Quality Index, and Exercise-induced Feeling Inventory. Data were analyzed using intent-to-treat methods. Results: Significant improvements in all outcome measures were found for both groups, with acute and cumulative benefits. Although the HDG showed greater improvements on all scales, between-group differences did not reach significance, possibly due to lack of power because of the small sample size. Cumulative yoga minutes were correlated with improvement in outcome measures. Limitation: This dosing study did not include a non-yoga control. Conclusions: Improvement in psychological symptoms correlated with cumulative yoga practice. Both interventions reduced symptoms of depression and anxiety and increased feelings of positivity. The time commitment for yoga practice needs to be weighed against benefits when designing yoga interventions.