Predictors of drug treatment response in obsessive-compulsive disorder

Although a large body of evidence indicates the efficacy of pharmacotherapy in the treatment of obsessive-compulsive disorder (OCD), a considerable percentage of these patients do not respond. Very few studies focus on factors related to treatment response of OCD. The purpose of this study was to investigate which clinical factors are related to drug treatment response in OCD.

We examined 53 OCD patients treated with either clomipramine or fluoxetine for a period of 6 months, dividing the sample into "responders" and "nonresponders" to treatment. At admission, patients were evaluated using a semistructured clinical interview, the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the Hamilton Rating Scale for Depression, and the Hamilton Rating Scale for Anxiety. We then compared acute-phase patient characteristics and response to drug treatment. Response was defined as a decrease of at least 40% in the Y-BOCS total score and a rating of "improved" or "very improved" on the Clinical Global Impressions scale within 16 weeks of treatment and maintained over three consecutive evaluations.

By the sixth month of treatment, 31 patients (58.5%) responded to either clomipramine or fluoxetine. Nonresponders had lower age at onset and longer duration of the disorder; in addition, they showed higher frequency of compulsions, washing rituals, chronic course, concomitant schizotypal personality disorder, and previous hospitalizations. A worse response to drug treatment was predicted in a stepwise multiple regression by (1) concomitant schizotypal personality disorder, (2) presence of compulsions, and (3) longer illness length.

Our findings suggest that there are distinct types of OCD with respect to drug treatment response. They provide indirect evidence of treatment specificity by identifying characteristics responsive to different modalities, which may be of value in the selection of patients for alternative treatments.