Defining clinical severity in adults with obsessive-compulsive disorder

The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) is the most commonly used instrument to assess the clinical severity of obsessive-compulsive symptoms. Treatment determinations are often based on Y-BOCS score thresholds. However, these benchmarks are not empirically based, which may result in non-evidence based treatment decisions. Accordingly, the present study sought to derive empirically-based benchmarks for defining obsessive-compulsive symptom severity.

Nine hundred fifty-four adult patients with obsessive-compulsive disorder (OCD), recruited through the Brazilian Research Consortium on Obsessive-Compulsive Spectrum Disorders, were evaluated by experienced clinicians using a structured clinical interview, the Y-BOCS, and the Clinical Global Impressions-Severity scale (CGI-Severity).

Similar to results in treatment-seeking children with OCD, our findings demonstrated convergence between the Y-BOCS and global OCD severity assessed by the CGI-Severity (Nagelkerke R(2)=.48). Y-BOCS scores of 0-13 corresponded with 'mild symptoms' (CGI-Severity=0-2), 14-25 with 'moderate symptoms' (CGI-Severity=3), 26-34 with 'moderate-severe symptoms' (CGI-Severity=4) and 35-40 with 'severe symptoms' (CGI-Severity=5-6). Neither age nor ethnicity was associated with Y-BOCS scores, but females demonstrated more severe obsessive-compulsive symptoms than males (d=.34). Time spent on obsessions/compulsions, interference, distress, resistance, and control were significantly related to global OCD severity although the symptom resistance item pairing demonstrated a less robust relationship relative to other components of the Y-BOCS.

These data provide empirically-based benchmarks on the Y-BOCS for defining the clinical severity of treatment seeking adults with OCD, which can be used for normative comparisons in the clinic and for future research.