Cognitive versus behavior therapy: Processes of change in the treatment of obsessive-compulsive disorder

Background: Behavior therapy [exposure and response prevention (ERP)] and cognitive therapy (CT) have proven effective in the treatment of obsessive-compulsive disorder. Direct comparisons between these treatment modalities have exposed no differences in efficacy. However, very little research has been conducted into the differences between the change processes in ERP and CT. This investigation is a first attempt to study change by measuring scores on a weekly basis rather than at specific stages in the treatment and follow-up. Methods: We used the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) at weekly intervals to rate and compare the severity of the obsessions and compulsions of 61 completers of either CT or ERP. The aim was to ascertain whether the process of change in CT is different from the process of change in ERP. We expected that ERP would primarily affect behavior, thus reducing compulsions first, while CT would primarily affect thought, thus reducing obsessions first. Results: Firstly, no differences were found between ERP and CT with respect to the change process for obsessions and compulsions. Secondly, it emerged that changes in compulsions predicted all treatment effects better than changes in obsessions. Conclusions: These results suggest that reduction of compulsions is the process through which both ERP and CT affect change.