Participants in the Bikram yoga group were asked to attend two classes per week for 8 weeks (16 classes in total) at a local affiliated Bikram yoga studio. Certified Bikram yoga teachers instructed all classes using a scripted instructional dialogue. Each 90-min class was held in a temperature-controlled room (40.6 degrees Celsius, 40% humidity). The class opened with a deep breathing exercise and continued with 50 minutes of standing asanas and 40 minutes of floor-based asanas, including a quick, forceful breathing exercise to finish. All but the last asana (i.e., spine-twisting) were performed twice. Savasana, which is a restorative and relaxation posture, was performed between asanas throughout the floor series and at the end of class. The yoga studio regularly offered 22 class times per week, all of which were accessible to participants.

Participants in the aerobic exercise group were asked to attend two group aerobic exercise classes per week for 8 weeks (16 classes in total) at the Kingston Family YMCA. They were provided with a modified schedule of the YMCA group classes, which included only classes with a strong aerobic component and excluded those involving yoga, pilates, or cycling. Selecting these classes was done in consultation with the general manager of the YMCA, who was familiar with each class type. Classes involving the following components were available to participants: choreography-based cardio, aerobics, light muscular conditioning, and stretching; cardio, plyometric, and strength training exercises; high intensity aerobic exercise with intermittent rest periods; circuit-based cardio and strength training exercises; stepper-based exercises; and Latin-inspired dance/fitness. Classes were 50-60 minutes in duration.

Waitlisted individuals were not able to access yoga or exercise classes throughout the intervention period but participated in the rest of the study protocol. Following the post-treatment assessment, they received access to the class type of their choosing.

Participants in the Bikram yoga group were asked to attend two classes per week for 8 weeks (16 classes in total) at a local affiliated Bikram yoga studio. Certified Bikram yoga teachers instructed all classes using a scripted instructional dialogue. Each 90-min class was held in a temperature-controlled room (40.6C, 40% humidity). The yoga studio regularly offered 22 class times per week, all of which were accessible to participants.

Treatment response was defined as a 50% reduction from pre-treatment assessment and post-treatment assessment on the Hamilton Rating Scale for Depression (HAM-D). The HAM-D is a 17-item semi-structured interview that assesses the severity of depressive symptoms in the past week. The item ratings range from 0 to 2 or from 0 to 4 depending on the item, with total scores ranging from 0 to 50. Higher scores indicate more severe depressive symptoms.

Remission was defined according to two criteria:

1. A post-treatment assessment Hamilton Rating Scale for Depression (HAM-D) score of 7 or lower. The HAM-D is a 17-item semi-structured interview that assesses the severity of depressive symptoms in the past week. The item ratings range from 0 to 2 or from 0 to 4 depending on the item, with total scores ranging from 0 to 50. Higher scores indicate more severe depressive symptoms.

   AND

2. No longer meeting diagnostic criteria for major depression. This was assessed by administering the major depression module of the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I/P). The major depression module of the SCID-I/P includes 9 questions corresponding to the 9 criterial symptoms of major depression. Each symptom is coded as 0-absent or 1-present. Total scores can range from 0-9. A total score of 5 or above indicates the presence of major depression. Scores below 5 indicate that the participant no longer meets criteria.

The Hassles and Uplifts Scale (HUS) examines commonly encountered events that may be considered irritants (i.e., hassles) and/or positive experiences (i.e., uplifts). More specifically, participants were asked to give weekly ratings of 53 events based on how much each event was a hassle and how much each event was an uplift in the previous week with the following scale: 0 = None or not applicable, 1 = Somewhat, 2 = Quite a bit, 3 = A great deal. Scores across items were summed to give separate cumulative scores for hassles and uplifts. For the purposes of this study, only hassles were examined in subsequent analyses. The range of possible scores for hassles is 0 to 159, with a higher score indicating greater hassles.