Comorbidity as a moderator of the differential efficacy of transdiagnostic behavior therapy and behavioral activation for affective disorders

Objective: Transdiagnostic psychotherapies have been proposed as an effective means for addressing the needs of patients with multiple, comorbid disorders. Yet, it remains unknown whether transdiagnostic approaches empirically outperform disorder-specific psychotherapies for patients with comorbid disorders. Thus, this study tested whether comorbidity moderated the efficacy of transdiagnostic behavior therapy (TBT) and behavioral activation (BA) for patients with various affective disorders. Methods: Data derived from a randomized controlled trial in which 93 treatment-seeking veterans received 12 sessions of TBT (n = 46) or BA (n = 47). Baseline comorbidity was assessed with a diagnostic interview. Patients rated their symptoms and functioning throughout treatment, and therapists recorded premature treatment discontinuation. Results: Multilevel models revealed significant interactive effects on changes in symptoms and functioning, but not on the posttreatment levels of these outcomes; whereas patients with more comorbidity experienced greater reductions in distress and symptom interference in TBT compared to BA, those with one disorder had better outcomes in BA. Similarly, whereas patients with more comorbidity were less likely to prematurely discontinue TBT compared to BA, those with one disorder were less likely to prematurely discontinue BA. Conclusions: The results lend empirical support to previously untested hypotheses for potential benefits of transdiagnostic psychotherapies.