1. ¹Department of Psychiatry, University of São Paulo Medical School, São Paulo, Brazil
2. ²Child Study Center, Yale University School of Medicine, New Haven, CT, USA
3. ³Department of Psychology, University of British Columbia, Vancouver, BC, Canada
4. ⁴Institute of Living, Hartford, CT, USA
5. ⁵Department of Psychiatry, Mt Sinai School of Medicine, New York, NY, USA
6. ⁶Graduate School of Medical Sciences, Kitasato University, Kanagawa, Japan

Correspondence: Dr JF Leckman, Child Study Center, Yale University School of Medicine, I-265 SHM, 230 South Frontage Road, New Haven, CT 06520-7920, USA. E-mail: james.leckman@yale.edu

Received 19 May 2005; Revised 18 November 2005; Accepted 15 December 2005; Published online 24 January 2006.

Abstract

Obsessive–compulsive disorder (OCD) encompasses a broad range of symptoms representing multiple domains. This complex phenotype can be summarized using a few consistent and temporally stable symptom dimensions. The objective of this study was to assess the psychometric properties of the Dimensional Yale–Brown Obsessive–Compulsive Scale (DY-BOCS). This scale measures the presence and severity of obsessive–compulsive (OC) symptoms within six distinct dimensions that combine thematically related obsessions and compulsions. The DY-BOCS includes portions to be used as a self-report instrument and portions to be used by expert raters, including global ratings of OC symptom severity and overall impairment. We assessed 137 patients with a Diagnostic and Statistical Manual-IV diagnosis of OCD, aged 6–69 years, from sites in the USA, Canada and Brazil. Estimates of the reliability and validity of both the expert and self-report versions of the DY-BOCS were calculated and stratified according to age (pediatric vs. adult subjects). The internal consistency of each of the six symptom dimensions and the global severity score were excellent. The inter-rater agreement was also excellent for all component scores. Self-report and expert ratings were highly intercorrelated. The global DY-BOCS score was highly correlated with the total Yale–Brown Obsessive–Compulsive Scale score (Pearson r=0.82, P<0.0001). Severity scores for individual symptom dimensions were largely independent of one another, only modestly correlated with the global ratings, and were also differentially related to ratings of depression, anxiety and tic severity. No major differences were observed when the results were stratified by age. These results indicate that the DY-BOCS is a reliable and valid instrument for assessing multiple aspects of OCD symptom severity in natural history, neuroimaging, treatment response and genetic studies when administered by expert clinicians or their highly trained staff.