Background: We tested the hypotheses that the addition of medication to psychotherapy enhances participation in the latter by: (1) speeding the acquisition of the psychotherapy's targeted skill; and (2) facilitating higher skill level acquisition.
Method: Participants were 431 chronically depressed patients who received Cognitive Behavioral Analysis System of Psychotherapy (CBASP), alone (N=214) or in combination with nefazodone (N=217), as part of a randomized chronic depression study (Keller et al. 2000). CBASP, developed specifically to treat chronic depression, uses a specific procedure, 'situational analysis' to help patients engage in more effective goal-oriented interpersonal behaviours. At the end of each session, therapists rated patients on their performance of situational analysis. Outcome on depressive symptoms was assessed with the 24-item Hamilton Rating Scale for Depression.
Results: Although reductions in depression were significantly greater in combined treatment compared to CBASP alone, there were no between-group differences in either the rate of skill acquisition or overall skill level at the end of treatment. Proficiency in the use of the main skill taught in psychotherapy at treatment midpoint predicted outcome independently of medication status and of baseline depressive severity.
Conclusions: Effective participation in CBASP, as reflected by proficiency in the compensatory skill taught in psychotherapy, is not enhanced by the addition of medication and does not mediate the between-group difference in depression outcome.