Many authors have separated obsessive-compulsive disorder (OCD) into several dimensions. Watson and Wu (2005) identified obsessive checking, obsessive cleanliness, and compulsive rituals as separate and only moderately related constructs and concluded that OCD may be both phenotypically and genotypically heterogeneous. Leckman et al. (1997) found four dimensions within the OCD criteria that were intercorrelated between .50 and .56, and Mathews, Jang, Hami, and Stein (2004) did as well. If the putative disorder has four dimensions, which tend to share only 25%–31% of their variance with each other, then, by definition, individuals can be high on one dimension without being high on another dimension: Elevation in obsessive checking does not necessitate, for example, elevation in hoarding. The putative disorder is a combination of only moderately related constructs, and those constructs may have distinct genetic etiologies. OCD may not, on the basis of these findings, be a homogeneous psychological construct. To assign an individual a diagnosis of OCD may therefore be imprecise.
