Two times four is four: OCD dimensions, classes, and categories.

Recent research on the phenomenology, etiology, and pathophysiology of pediatric obsessive-compulsive disorder (OCD) signals a renewed interest in pediatric neuropsychiatric disorders. Pediatric OCD is one of the few disorders that mimic the adult form of the disorder in its breadth and depth; that is, it appears in a full-blown form even in prepubertal ages. This is not the case for schizophrenia, bipolar disorder, or major depression. Following the paradigm of early-onset diabetes and other pathophysiologically better understood diseases, pediatric OCD is plausibly more biologically driven or more genetic than its adult-onset form. This greater biological relevance is demonstrated by family studies that find higher rates of familial OCD when child OCD probands are used. In this vein, one of the most active research domains in OCD, is the search for biologically meaningful subphenotypes that would facilitate etiological research, including gene discovery. In this issue of the Journal, Mataix-Cols et al. and Stewart et al. examine the symptom architecture of pediatric OCD using data reduction techniques that have been widely used in the adult OCD literature. Mataix-Cols et al. consider whether symptom dimensions in pediatric OCD are preserved with respect to symptoms dimensions in adult OCD samples. In the adult OCD literature, four factors are commonly reported to explain variance using principal components analysis (PCA): contamination/cleaning, aggressive/sexual/religious obsessions, ordering/symmetry, and hoarding. The statistical technique used by Mataix-Cols et al. on a sample of 238 children and adolescents takes a similar approach to those previously reported, namely, semiquantitative data (symptom counts within particular categories) submitted to PCA with varimax rotation. The four derived factors are comparable to adult PCA symptom dimension factors, with the exception that hoarding is comingled with checking symptoms in the child sample. Interestingly, in this child sample, hoarding was correlated with OCD-related measures of slowness, responsibility, indecisiveness and doubt, and higher depression severity and was more common in girls compared to boys, highlighting a particularly vulnerable subset of children with OCD. In turn, Stewart et al. report on a confirmatory factor analysis (CFA) of three age group samples: children, adolescents, and adults with OCD. This ambitious article is a tour de force in OCD symptom data reduction. Although the limitations of the methods and sampling leave some questions unanswered, this study does advance research in the field. Using cross-sectional samples, modelfitting methods are applied to measure fit of these data to the Summerfeldt et al. four-factor solution. Summerfeldt et al. had applied CFA testing of three-, fourand five-factor models, concluding that the four-factor model best fit OCD category symptom, but not item-level, data in adults. This category symptom analysis assumes that the 60+ symptoms listed in the Yale-Brown Obsessive Compulsive Scale are grouped correctly into 13 categories. In Stewart et al., categorical data on the three different age samples are used to test the fit of the data to the Summerfeldt et al. four-factor solution. The results show that, in fact, the four-factor solution continues to best fit OCD categorical symptom data in each of the three samples across ages using multiplegroup CFA. In summary, the analyses by Mataix-Cols et al. and Stewart et al. of OCD symptom structure in youths yield four-factor solutions similar to those in Summerfeldt et al. The authors note that although there is similarity in symptom structure across ages, this is suggestive but not confirmatory of symptom stability. Taken together, these results, although Accepted March 10, 2008. Drs. Grados and Riddle are with the Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine. Correspondence to Dr. Marco A. Grados, 600 N. Wolfe Street, CMSC 346, Baltimore, MD 21287; e-mail: mjgrados@jhmi.edu. 0890-8567/08/4707-0731*2008 by the American Academy of Child and Adolescent Psychiatry. DOI: 10.1097/CHI.0b013e318173f720 E D I T O R I A L