Use of Factor-Analyzed Symptom Dimensions to Predict Outcome With Serotonin Reuptake Inhibitors and Placebo in the Treatment of Obsessive-Compulsive Disorder

OBJECTIVE: No consistent predictors of outcome have been identified for the pharmacotherapy of obsessive-compulsive disorder (OCD). Recent factor analytic studies have identified meaningful symptom dimensions that may be related to response to serotonin reuptake inhibitors and other treatments. METHOD: A total of 354 outpatients with primary OCD were administered the Yale-Brown Obsessive Compulsive Scale Symptom Checklist, and its 13 main symptom categories were factor analyzed by using principal components analysis. The identified symptom dimensions were then entered into multiple regression models as outcome predictors of response to serotonin reuptake inhibitors and placebo response in a group of 150 nondepressed subjects who completed six double-blind, placebo-controlled trials with a serotonin reuptake inhibitor (clomipramine, fluvoxamine, fluoxetine, sertraline, and paroxetine). Eighty-four patients received a serotonin reuptake inhibitor and 66, placebo. RESULTS: The principal components analysis identified five factors that explained 65.5% of variance in outcome: symmetry/ordering, hoarding, contamination/cleaning, aggressive/checking, and sexual/religious obsessions. Serotonin reuptake inhibitors were significantly superior to placebo on all outcome measures. Initial severity of OCD was related to greater posttreatment severity of OCD. Higher scores on the hoarding dimension predicted poorer outcome following treatment with serotonin reuptake inhibitors, after control for baseline severity. No predictors of placebo response were identified. Exclusion of clomipramine did not modify the overall results, suggesting a cross-serotonin reuptake inhibitor effect. CONCLUSIONS: The identified symptom dimensions are largely congruent with those identified in earlier reports. Patients with OCD vary in their response to treatment with serotonin reuptake inhibitors. The presence of hoarding obsessions and compulsions is associated with poorer response to serotonin reuptake inhibitors.