Duration and regularity of therapy attendance as predictors of treatment outcome in an adult outpatient population

The authors extend previous research examining the dose-effect relationship in psychotherapy (e.g., K. I. Howard, S. M. Kopta, M. S. Krause, & D. E. Orlinsky, 1986) by using a measure of amount of treatment that included both number of sessions attended and treatment duration. Participants were 74 adult patients attending an outpatient community mental health clinic. A multiple regression analysis found no main effects for either measure of treatment length, but their interaction added a significant increase (DeltaR(2) = 6.2%, p < .05) in the prediction of patient outcome. For patients attending 11 or fewer sessions, more months in treatment was associated with worse outcome (r = 0.34, p < .05). Duration of treatment was unrelated to improvement for those attending more sessions. The findings of this study underscore the importance of regular therapy attendance for those patients scheduled for fewer sessions and suggest that clinicians should reconsider any temptation to spread allotted sessions over the course of a longer period when afforded fewer sessions by managed care.