Beyond Symptom Reduction: The Causal Effect of Cognitive Behavioral Therapy on Interpersonal Problems

Objective: Interpersonal problems are important transdiagnostic features in the development and treatment of mental disorders. However, evidence on causal effects of cognitive behavioral therapy (CBT) and differential treatment effects on interpersonal problems is scarce. Therefore, this study examines whether modern routine outpatient CBT more strongly reduces interpersonal problems than a naturalistic waitlist control condition. Potential heterogeneity of treatment effects is inspected, specifically focusing on differences in childhood emotional neglect and abuse. Method: Using observational data of outpatients with various mental disorders at three measurement points (intake on a waitlist, pre- and post-therapy assessments), we construct two treatment arms (NCBT = 256 vs. Nwaiting condition = 431) and train a Causal Forest to estimate treatment effects on interpersonal problems, given observed covariates. Results: Our results indicate a robust, moderate effect of CBT on interpersonal problems while fostering a dominant interpersonal style. Neither broad nor specific tests of heterogeneity indicate differential treatment effects. Conclusion: Although the findings are subject to methodological limitations and should be interpreted cautiously, they provide preliminary evidence that CBT may be an effective and broadly applicable treatment for interpersonal problems. Future randomized controlled trials are needed to confirm these results and establish causal inference.