Can Early Improvement be an Indicator of Treatment Response at Twelve Weeks in Obsessive Compulsive Disorder? Implications for Early-Treatment Decision-Making

Abstract

Background: Delayed onset of response to serotonin reuptake inhibitors represents a challenge in obsessive-compulsive disorder (OCD) treatment. In depression, absence of improvement in the first weeks has been raised as a motive to switch antidepressants before full non-response is observed. We aimed to investigate if early improvement is a predictor of OCD outcome after 12 weeks. Methods: Participants (n=150) were admitted to a specialized OCD outpatient program. Inclusion criteria: age 18-65, DSM-IV diagnosis of OCD, minimum baseline Yale-Brown Obsessive Compulsive Scale(Y-BOCS) score of 16, absence of previous pharmacological treatment for OCD. Fluoxetine was used up to 80mg/day. Systematic assessments were taken at baseline, weeks 4 and 12. Non-improvement at 4-weeks was defined as no reduction of baseline Y-BOCS scores. Response at 12 weeks was defined as 35% or greater decrease in baseline Y-BOC score. Spearman correlation, linear regression and chi-square test were performed to test the relationship between improvement at 4-weeks and the 12-weeks outcome. Results: Mean Y-BOCS scores(SD) at baseline, 4 and 12 weeks were, respectively: 27.3(5.4), 22.8(6.9) and 20.8(8.3). Correlation coefficient for 4-weeks improvement and 12-weeks outcome was 0.43(p=0.01). Linear regression analysis showed no-effect of the covariates on 12-weeks outcome and confirmed the relationship between improvement at 4-weeks and outcome at 12 weeks (β coef= 0.44, p< 0.01). Only five (11.9%) non-responders at 4-weeks were responders at 12-weeks (Pearson Chi-Square= 9.1, p= 0.003). Conclusions: Early improvement predicted 12-weeks outcome of OCD, which may have a role in early decision-making in OCD treatment.