Clinical Predictors of Drug Nonresponse in Obsessive-compulsive Disorder

Objective: Obsessive-compulsive disorder (OCD) is often a chronic and disabling illness with high comorbidity. Serotonin reuptake inhibitors (SRIs) are effective in treating OCD. However, 40% to 60% of patients with OCD do not respond adequately to SRIs. This study aims to identify the clinical predictors of nonresponse to SRIs in OCD by comparing SRI responders and nonresponders.

Method: 122 subjects with a diagnosis of DSM-IV OCD of at least 1 year's duration and with treatment history of adequate trials with at least 2 SRIs were recruited from December 2002 to March 2004. Of these, 67 were SRI responders and 55 were SRI nonresponders; they were compared on various clinical parameters. Nonresponse was defined as a score of >/=3 on the Clinical Global Impressions-Improvement sub-scale (CGI-I) after at least 2 adequate trials with SRIs. Response was defined as a score of 1 or 2 on the CGI-I.

Results: In regression analysis, baseline severity of OCD (p = .049), comorbid major depressive disorder (p = .005), presence of sexual obsessions (p = .002), and washing (p = .008) and miscellaneous compulsions (p = .013) were identified as predictors of nonresponse to SRIs. Early age at onset showed a trend toward prediction of nonresponse (p = .056). In the univariate analysis, mixed OCD (p = .001) and poor insight (p = .023) were associated with nonresponse.

Conclusion: This study has identified clinical predictors of nonresponse to SRIs. These predictors may have to be taken into consideration and assessed carefully when SRIs are prescribed to treat OCD. Future studies should aim at identifying treatment modalities that are effective in SRI nonresponders.