Session-specific effects of the Metacognitive Group Training for Obsessive-Compulsive Disorder: significant results for thought control.

The investigation of the session-specific effects is central for the understanding of psychological interventions. For the present study, we investigated the session-specific effects of the Metacognitive Group Training for Obsessive-Compulsive Disorder (MCT-OCD), which was revised based on data of a pilot study. Thirty-four outpatients with OCD participated in the MCT-OCD once a week over 8 weeks. Different metacognitive beliefs (e.g., thought control) and cognitive beliefs (e.g., intolerance of uncertainty), OC symptoms, as well as associated comorbid symptoms were assessed before and after each session. Linear mixed effects models showed that patients' obsessions and compulsions, thought control, the belief of being well informed about the disorder, and action fusion improved over the course of the training. The only session-specific effect emerged for thought control, which improved immediately after the respective module. We were able to replicate the findings of the pilot study and thus corroborate the session-specific effect of the module targeting thought control. Moreover, we generated information on the mode of action of the individual modules of the MCT-OCD that allows a more in-depth evaluation of the intervention. Notably, we were able to eliminate the adverse effects of the pilot version of the MCT-OCD.Trial Registration: German Clinical Trials Register (Deutsches Register Klinischer Studien [DRKS]; DRKS-ID: DRKS00013539; registration date: 22/02/2018).