The relationship between miscellaneous symptoms and major symptom factors in obsessive-compulsive disorder.

The diverse symptomatology of obsessive-compulsive disorder (OCD) is being increasingly regarded as reducible to a few symptom dimensions. However, prevailing factor-analytically derived models of symptom structure omit a number of the well-recognized "miscellaneous" symptoms of OCD. This study sought to determine whether miscellaneous OCD symptoms, ascertained by the Yale-Brown Obsessive-Compulsive Scale symptom checklist, could be differentially and reliably predicted by four symptom factors (obsessions and checking, symmetry and ordering, contamination and cleaning, and hoarding) in two independent groups of individuals with OCD (n=381 and n=107). Logistic regression analyses were used to determine the association of each of the miscellaneous symptoms with the symptom factors; then a single confirmatory factor analysis was conducted to test the model of associations in the smaller sample. Sixteen (89%) of the 18 symptoms examined were reliably predicted by one (11 items) or two (5 items) of the factors, with obsessions and checking and symmetry and ordering emerging as foremost predictors. The expanded four-factor model showed good fit with data from the second sample. Results are conceptually meaningful, but suggest the inadequacy of groupings based solely upon overt behaviors. These findings may aid clinical understanding of OCD and be of value to studies using symptom factors to guide investigation of its causes and correlates.