Supplementary Material for: Short-term psychodynamic therapy of obsessive-compulsive disorder – a randomized controlled trial of unmedicated patients

Background: Obsessive-compulsive disorder (OCD) is a chronic and disabling mental disorder. Cognitive-behavioral therapy and serotonin-reuptake inhibitors and their combination are first-line treatments. However, about 50% of the patients do not achieve response or remission, although many patients received additional pharmacotherapy. These results highlight the need for additional evidence-based treatment options. Methods: In a randomized controlled trial (RCT) a manual-guided method of short-term psychodynamic therapy (STPP) for OCD was tested against a waiting list condition. Thirty-seven unmedicated patients were randomly assigned to STPP, 30 to the waiting list. The Y-BOCS total score post-therapy assessed by trained and masked raters was the primary outcome. Secondary outcomes included response, remission, depression, interpersonal problems and obsessive beliefs. Results: In the intention-to-treat sample, STPP achieved a significantly lower Y-BOCS score (p < 0.0001) than the waiting list condition, associated with a large between-group effect size (d=1.04). The mean difference of change in the Y-BOCS between baseline and post-therapy or waiting period assessment was -11.49 (95% CI -14.36, -8.63) for STPP and –1.10 (95% CI -4.29, 2.10) in the waiting-list. Remission rates were 55% vs 17% (p=0.0012), response rates 64% vs 17% (p=0.0003) in favor of STPP. Conclusion: In a first RCT, manual-guided STPP proved to be efficacious in OCD, thereby broadening the spectrum of evidence-based interventions. Of note, our study is one of the few trials using psychotherapy as a monotherapy in OCD, showing effects of psychotherapy alone. Further research is needed to replicate these findings and to compare STPP with other established treatments.