Clinical supervision is a cornerstone in psychotherapists' training but there are few empirical evaluations on the effects of supervision on therapists' competencies. The aim of this study was therefore to evaluate the effects of standardized supervision on rater-assessed competency in Cognitive Behavior Therapy (CBT). Six therapists with basic training in CBT were provided with protocol-based clinical supervision in CBT in a single-case experimental multiple baseline design. The supervision focused on specific CBT competencies and used experiential learning methods such as role-play. Each therapist recorded weekly treatment sessions during phases without and with supervision. The therapists' CBT competence was assessed by third-party raters using the Revised Cognitive Therapy Scale (CTS-R). Statistical analyses showed that the therapists' CTS-R scores increased significantly during the phase with supervision with a mean item increase of M = 0.71 (range = 0.50-1.0) on the supervision focus areas. This is one of the first empirical studies that can confirm that supervision affect CBT competencies. The results also suggest that supervision can be manualized and that supervisees have a positive perception of more active training methods. Further studies are needed to replicate the results and to find ways to improve the impact of supervision.
Keywords: Supervision; cognitive behavior therapy; single-case design; therapeutic competence.