Factor structure of the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) in a large sample of patients with schizophrenia or related disorders and comorbid obsessive-compulsive symptoms

In the past decade there has been an increasing interest in the levels of obsessive-compulsive symptoms (OCS) found in patients with schizophrenia or related disorders. The widely acknowledged gold standard measure of the severity of OCS is the content-free version of the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) (Goodman et al., 1989a,b). However, factor analytic research in patients with obsessive-compulsive disorder (OCD) provided varied results. So far no study has been conducted on the factor structure of the Y-BOCS in patients with schizophrenia. The present study addresses this issue. We administered the Y-BOCS in a sample of 217 patients with schizophrenia or related disorders and comorbid OCS who participated in a multicentre cohort study. We used principal component analysis (PCA) to explore the underlying factor structure. A two-factor solution consistent with the originally proposed scoring structure of the Y-BOCS provided the optimal fit. We also found some support for a three-factor solution consistent with earlier findings by Kim et al. and Moritz et al. (Kim et al., 1994; Moritz et al., 2002). The produced factors showed good reliability and strong correlations with the Y-BOCS Total score. However, the resistance to compulsion item failed to demonstrate adequate correlation to the Total score, a finding consistent with earlier findings in several studies with patients with OCD.