Abstract P222: Sex Moderates Treatment Effects in Integrated Behavior Therapy for Comorbid Obesity and Depression

Introduction: Obesity and depression often co-occur, especially in women. Efficacious treatments exist for both conditions, but treatment outcomes vary. Assessing sex-specific responses to integrated therapy of these conditions could inform opportunities for tailoring. Hypothesis: Sex will significantly moderate the effects of an integrated collaborative care intervention on weight loss and depression outcomes through 24 months. Short-term treatment response at 6 months will reliably predict 12- and 24-month outcomes by sex. Methods: We conducted secondary analyses using data from the RAINBOW trial, which demonstrated efficacy of an integrated collaborative care intervention at reducing weight (BMI) and depression severity (SCL-20) at 12 months relative to usual care in adults with obesity and depression. Linear mixed models were used to assess treatment effects by sex, an a priori hypothesized biological moderator, on BMI and SCL-20 at 6, 12, and 24 months. Areas under the receiver operating characteristic curves (AUCs) based on logistic regressions were used to assess sex-specific thresholds of weight loss (%) and SCL-20 reduction at 6 months that reliably predicted clinically significant weight loss (i.e., ≥5% of baseline weight) and depression response (i.e., ≥50% decrease in SCL-20 scores) at 12 and 24 months. Results: Sex significantly moderated the treatment effects on BMI and SCL-20. Compared with women, men achieved significantly greater reductions in BMI at 6, 12, and 24 months in the intervention relative to usual care. Compared with men, women achieved significantly greater reductions in SCL-20 at 12 months only in the intervention relative to usual care. AUCs in the logistic models were similar for both sexes: >0.82 at 12 months and >0.65 at 24 months predicting clinically significant weight loss; >0.70 at 12 months and >0.67 at 24 months predicting clinically significant depression response. With 80% specificity to ensure good probability of correctly identifying participants not achieving longer-term outcomes of clinical significance, women who lost 2.5-3.0% weight and men who lost 3.4-4.1% weight at 6 months were likely to achieve ≥5% weight loss at 12 and 24 months. Similarly, women who reduced SCL-20 by 0.70 and men who reduced by 0.60-0.65 were likely to achieve ≥50% decrease in SCL-20 at 12 and 24 months. Conclusions: The treatment effects of this integrated intervention for obesity and depression differed significantly by sex, with men showing greater weight loss and women showing greater depression reduction. Sex-specific short-term responses at 6 months were identified for predicting clinically significant weight loss and depression outcomes at 12 and 24 months. Results suggest that sex may be an important tailoring variable when designing collaborative care interventions.