Therapist effects in the National Institute of Mental Health Treatment of Depression Collaborative Research Program

Recent psychotherapy research literature has stressed the importance of therapist effects (i.e., the impact of the individual therapist on treatment outcome). The authors report an analysis of therapist effects in the National Institute of Mental Health Treatment of Depression Collaborative Research Program using hierarchical linear modeling. In addition to studying overall therapist effects, they investigate the possible interaction of therapists with initial patient severity and difficulty levels. There were virtually no significant findings in regard to either overall effects of therapists or the interaction with patient severity and difficulty. There was some suggestion of outliers (i.e., therapists who had especially good [or poor] rates of patient retention and recovery). Recommendations are made regarding different methodological approaches for studying outcome differences due to therapists.