Symptom dimensions in obsessive-compulsive disorder: factor analysis on a clinician-rated scale and a self-report measure

Although obsessive-compulsive disorder (OCD) is regarded as a unitary nosological entity, it encompasses a rich variety of heterogeneous mental and behavioural phenomena. The identification of clinical subtypes within this broad concept has been a focus of attention in recent years. In the present study, we administered a clinician-rated scale, the Yale-Brown Obsessive Compulsive Scale (Y-BOCS) with the Y-BOCS Symptom Checklist (Y-BOCS CL), as well as a self-report questionnaire, the Padua Inventory revised (PI-R), to 150 outpatients with OCD. A principal component analysis on the Y-BOCS CL, along with the PI-R, identified 6 consistent symptom clusters: (1) contamination obsessions and cleaning compulsions, (2) sexual/religious/somatic obsessions and checking, (3) high risk assessment and checking, (4) impulses and fear of loss of control, (5) need for symmetry and exactness, and ordering and counting compulsions, and finally (6) rumination. The Y-BOCS CL and PI-R showed great overlap and consistency regarding content and severity of the OCD symptoms. On inspection of items with identical content, only half of the items showed significant agreement. Both inventories have unique factors: rumination is represented solely in the PI-R, somatic obsessions and checking solely in the Y-BOCS CL. This means that the use of both clinician-administered and self-report measures is recommended, so that the entire spectrum of symptoms is represented.