Cognitive Behavioral Therapy for Psychosis (CBTp): Multicenter Randomized Clinical Trial on Specific Efficacy

Abstract

Background: Cognitive behavioral therapy for psychosis (CBTp) is a specific form of psychotherapy recommended in evidence-based treatment guidelines for patients with psychosis. However, it remains unclear whether CBTp is more efficacious than unspecific psychotherapies such as supportive therapy (ST). Methods: This multicenter, single blind, randomized clinical trial used a parallel group design to compare CBTp and ST. In total, 330 patients with persistent positive symptoms were included. Participants received 20 sessions of CBTp or ST over a 9-month period. Therapy was provided in six outpatient clinics at university psychiatry departments. The primary endpoint was the severity of positive symptoms (Positive and Negative Syndrome Scale-positive) until post-treatment at 9 months after inclusion. Analysis was carried out by intention to treat with multilevel linear modeling. Findings: There was a between group effect size of g=0·33 (0·11-0·55) in favor of CBTp for positive symptoms, with pre-post effect sizes of g=0·93 (0·70-1·15) for CBTp and g=0·62 (0·40-0·84) for ST. CBTp showed favorable effects for hallucinations and social functioning, but not for negative symptoms and readmission rates. Ratings of the therapeutic relationship, number of adverse events, and antipsychotic medication did not differ between the groups. Positive symptoms decreased in both groups until the 24 month follow-up, with a between group difference of g=0·09 (-0·23-0·39). Interpretation: CBTp is more efficacious than ST in patients with persistent positive symptoms. CBTp effects cannot be explained by therapeutic attention alone. This indicates CBTp has specific mechanisms of action, and further supports the unrestricted recommendation of CBTp for the treatment of psychosis. Trial Registration Number: ISRCTN29242879 Funding Statement: The study was funded by the German ministry of education and research (grant no. 01GV0618). Declaration of Interests: All authors declare that there is no conflict of interest. Ethics Approval Statement: The study protocol was reviewed without objections by the ethics committee of the coordinating study center and the local ethics committees of all participating centers. Patients were included in the study after written informed consent was obtained, which was assured by external monitoring.