Cognitive Behavioral Analysis System of Psychotherapy (CBASP) vs. Behavioral Activation (BA) in Persistently Depressed Treatment-resistant Inpatients: Efficacy, Moderators, and Mediators of Change

About half of all psychiatric inpatients with depression suffer from persistent depressive disorder (PDD). Given their high degree of treatment-resistance (TR), comorbidity, suicidality, and hospitalization rates, this patient group appears to be particularly difficult to treat and, from a health economic perspective, constitutes a major challenge. The Cognitive Behavioral Analysis System of Psychotherapy (CBASP) is the only psychotherapy specifically tailored for PDD. Originally developed as an outpatient treatment by James P. McCullough, CBASP has been modified for the severely ill PDD patients with TR as a multimodal inpatient concept. Pilot studies indicate very good feasibility and promising outcome. Therefore, a randomized controlled trial is now mandatory for testing the superiority of the inpatient CBASP program vs. the evidence-based Cognitive Behavioral Therapy (CBT), the 'gold standard' in depression treatment. Behavioral Activation (BA) was chosen as the control intervention because BA, as a specific variant of CBT, is at least as effective as standard CBT in severely depressed patients while being easier to train and implement in inpatient settings. Both therapies will be applied as a treatment-phase program (10-week inpatient/ dayclinic acute treatment followed by 6-week outpatient continuation group-treatment) in combination with standardized and guideline-based pharmacotherapy. The proposed prospective, multi-center, randomized study with 396 PDD patients with TR will therefore address the primary research question: Is the CBASP program more effective than the BA program in this patient group? The primary hypothesis is that after 16 weeks of treatment, CBASP will show a significant superiority over BA in reducing depressive symptoms. In addition, the important psychotherapy research question: what works for whom and why? will be addressed.

Moderator analyses will examine whether child maltreatment and methylation of exon IV of the BDNF gene have an impact on the differential efficacy of the treatments. Regarding mediator analyses, it will be examined whether the differential efficacy of the treatments can be explained by treatment-specific changes in interpersonal problems or activity levels. A follow-up survey 48 weeks after the end of the interventions will provide valuable results regarding the long-term outcome of the treatments. Finally, the health economic potential of the interventions will be investigated through cost-benefit analyses in order to provide important information on the cost-effectiveness of implementation in routine care for health policy. Thus, the results of this study will have the potential to relieve the burden of this very serious and cost-intensive disorder while improving human health. In addition, moderator and mediator analyses may guide personalized treatment and enable therapists to more specifically address psychotherapeutic needs of individual PDD patients in the future.