Validity of Controlled Clinical Trials of Psychotherapy: Findings From the NIMH Treatment of Depression Collaborative Research Program

OBJECTIVE: This research extends a series of studies that have examined the process of psychotherapy. The authors hypothesized that manualized regimens of psychotherapy compared in a controlled clinical trial would overlap considerably in process and technique and that intervention strategies common to both treatments would be responsible for promoting patient change. METHOD: Expert therapists developed prototypes of the ideal regimens of brief interpersonal psychotherapy and cognitive behavior therapy using the Psychotherapy Process Q-Set, an instrument designed to provide a standard language for describing treatment processes. A separate set of clinical judges then used the Psychotherapy Process Q-Set to score the actual transcripts of interpersonal psychotherapy and cognitive behavior therapy sessions conducted as part of the NIMH Treatment of Depression Collaborative Research Program. The expert prototypes were then compared with actual therapy administered in order to determine the extent to which each form of therapy conformed to its ideal prototype. RESULTS: Both the interpersonal psychotherapy and cognitive behavior therapy sessions adhered most strongly to the ideal prototype of cognitive behavior therapy. In addition, adherence to the cognitive behavior therapy prototype yielded more positive correlations with outcome measures across both types of treatment. CONCLUSIONS: Relying on brand names of therapy can be misleading. These findings suggest that the basic premise of controlled clinical trials (i.e., that the compared interventions represent separate and distinct treatments) may not have been met in the NIMH Treatment of Depression Collaborative Research Program. The implications of these findings for using controlled clinical trials to study psychotherapy are discussed.