Augmenting serotonin reuptake inhibitors in obsessive-compulsive disorder: What moderates improvement?

Abstract

Patients with obsessive-compulsive disorder (OCD) often only partially respond to serotonin reuptake inhibitors (SRIs). In such cases, American Psychiatric Association practice guidelines suggest augmenting SRIs with cognitive-behavioral therapy consisting of exposure and ritual prevention (EX/RP) or antipsychotic medication (i.e., risperidone). We examined moderators and predictors of these 2 augmentation strategies. Data came from a randomized controlled trial that compared adding EX/RP or risperidone to SRIs in adults with OCD. Patients entered the study on a stable SRI dosage and were randomized to EX/RP (N = 40), risperidone (N = 40), or placebo (N = 20). Data were analyzed using multilevel modeling. Pretreatment OCD severity, age, and depression were significant moderators. Although OCD severity was unrelated to EX/RP response, individuals with more severe OCD had poorer outcomes and slower improvement with risperidone. Increasing age predicted better response to risperidone, but not EX/RP. Increased depression predicted poorer response to placebo, but not EX/RP or risperidone. Poorer functioning predicted worse outcome across all 3 conditions. Together, these moderators and predictor accounted for 33% of the variance in outcomes, above and beyond the 30.8% accounted for by treatment condition. SRI augmentation with EX/RP was more effective than risperidone across all of the demographic and clinical variables tested. EX/RP's superiority over risperidone increased with baseline OCD severity and with younger age. These data indicate that EX/RP should be the recommended SRI augmentation strategy, even for severe OCD. What determines the degree of EX/RP response in individual patients deserves further study.