Association of Cotherapy Supervision With Client Outcomes, Attrition, and Trainee Effectiveness in a Psychotherapy Training Clinic


  • This article is based on a doctoral dissertation completed by the first author under the supervision of the coauthors, submitted to American University in partial fulfillment of the requirements for a doctorate.

Please address correspondence to: David A. F. Haaga, Department of Psychology, Asbury Building, American University, Washington, DC 20016–8062. E-mail:



Cotherapy supervision has been hypothesized to enhance client outcomes and trainee effectiveness, but there is little empirical evidence relevant to either claim. This study tested both hypotheses, using data from the supervision of psychology doctoral students conducting cognitive behavioral therapy in a university-based clinic.


Groups of clients treated by supervisor-trainee duos and groups of clients treated by solo trainees with varying exposure to cotherapy supervision were compared on changes in symptoms as measured with the Outcome Questionnaire (OQ-45) and on dropout rates.


Clients showed statistically significant reductions in symptoms from pretreatment to posttreatment. However, there were no significant group differences in the magnitude of change or in client retention.


No support was obtained for the hypothesized benefits of cotherapy supervision. Clients treated by a cotherapy (supervisor and supervisee) team did not improve more than did clients treated by solo trainees. Furthermore, clients treated by (solo) trainees who had received cotherapy supervision did not improve more than did clients treated by trainees who had not received cotherapy supervision.