Examining cognitive-behavioral therapy change mechanisms for decreasing depression, weight, and insulin resistance in adolescent girls at risk for type 2 diabetes.

OBJECTIVE: Depression in adolescence is linked to risk for type 2 diabetes (T2D). In this secondary data analysis of a randomized controlled trial comparing cognitive-behavioral therapy (CBT) to a control program to ameliorate insulin resistance via reducing depression symptoms, we examine which CBT change mechanisms (e.g., behavioral activation, cognitive restructuring) contributed to decreased depression and subsequent improvements in body mass index (BMI), percent body fat, and insulin resistance. METHODS: Girls 12-17y with overweight/obesity and family history of T2D were randomized to six-week group CBT (n = 61) or health education (HealthEd; n = 58). At baseline and post-treatment, adolescents completed questionnaires assessing activities, thoughts, and depression symptoms. At baseline, post-treatment, and one-year, BMI was calculated and insulin outcomes were derived from two-hour oral glucose tolerance testing. At baseline and one-year, percent body fat was assessed with dual-energy x-ray absorptiometry. Indirect effects of CBT components were tested on one-year changes in BMI, percent body fat, and insulin indices through decreases in depression symptoms during treatment. Intervention was tested as a moderator. RESULTS: In CBT, but not HealthEd, there was an indirect effect of increased physical activity during treatment on decreased one-year BMI via reductions in depression symptoms during treatment. Also, there were conditional indirect effects in CBT of increased pleasantness of physical and social activity during treatment on decreased one-year BMI via decreased depression symptoms during treatment. CONCLUSION: Behavioral activation may be a useful intervention to decrease depression and reduce excess weight gain in the targeted prevention of T2D in at-risk adolescent girls. NCT01425905, clinicaltrials.gov.