Background: Evidence indicates that obsessive--compulsive disorder (OCD) co-occurs with schizophrenia and bipolar disorder (BD) at a higher rate than in the general population. The inflated rate of comorbidity may result from chronic illness, antipsychotic therapy or treatment-seeking behavior. To control for these factors we evaluated the prevalence of OCD in patients with first-episode acute mania who met DSM-IV criteria for BD-I, and compared them with our previously reported group of first-episode schizophrenia patients.
Method: Fifty-six BD-I patients with a first-episode of acute mania were screened for OCD and additional comorbid disorders using the Structured Clinical Interview for DSM-IV Axis-I disorders and appropriate rating scales.
Results: Only one patient (1.8%) met DSM-IV criteria for OCD, and two (3.6%) met criteria for sub-threshold OCD. In contrast, there was a substantial aggregation of substance use disorders 32.1% (N=8), anxiety disorders, other than OCD 26.8% (N=15) and eating disorders 14.3% (N=8).
Limitations: Small sample size, cross-sectional nature of the assessments and the inclusion of only BD-I patients.
Conclusion: The rate of OCD in first-episode BD-I patients did not differ significantly from that found in the general population and was substantially lower than in previously reported first-episode schizophrenia patients (1.8% vs. 14%). We suggest that a preferential association of OCD with schizophrenia early in the course of illness represents a pathophysiological linkage between the two disorders, and putatively a specific schizo-obsessive subtype. In contrast, OCD in BD-I may stand for "true" comorbidity. Large-scale parallel comparative evaluations of comorbidity in BD-I and schizophrenia may contribute to the search for specific pathophysiological mechanisms of distinct comorbid-related subsets in either disorder.