Am J Psychiatry Published October 15, 2008
doi: 10.1176/appi.ajp.2008.08020320
© 2008 American Psychiatric Association

Meta-Analysis of the Symptom Structure of Obsessive-Compulsive Disorder

Michael H. Bloch, M.D., Angeli Landeros-Weisenberger, M.D., Maria C. Rosario, M.D., Ph.D., Christopher Pittenger, M.D., Ph.D., and James F. Leckman, M.D.

Objective: OCD is a clinically heterogeneous condition. This heterogeneity has the potential to reduce power in genetic, neuroimaging, and clinical trials. Despite a mounting number of studies, there remains debate regarding the exact factor structure of OCD symptoms. The authors conducted a meta-analysis to determine the factor structure of the Yale-Brown Obsessive Compulsive Scale Symptom Checklist. Method: Studies were included if they involved subjects with OCD and included an exploratory factor analysis of the 13 Yale-Brown Obsessive Compulsive Scale Symptom Checklist categories or the items therein. A varimax-rotation was conducted in SAS 9.1 using the PROC FACTOR CORR to extract factors from sample-size weighted co-occurrence matrices. Stratified meta-analysis was conducted to determine the factor structure of OCD in studies involving children and adults separately. Results: Twenty-one studies involving 5,124 participants were included. The four factors generated were 1) symmetry: symmetry obsessions and repeating, ordering, and counting compulsions; 2) forbidden thoughts: aggression, sexual, religious, and somatic obsessions and checking compulsions, 3) cleaning: cleaning and contamination, and 4) hoarding: hoarding obsessions and compulsions. Factor analysis of studies including adults yielded an identical factor structure compared to the overall meta-analysis. Factor analysis of child-only studies differed in that checking loaded highest on the symmetry factor and somatic obsessions, on the cleaning factor. Conclusions: A four-factor structure explained a large proportion of the heterogeneity in the clinical symptoms of OCD. Further item-level factor analyses are needed to determine the appropriate placement of miscellaneous somatic and checking OCD symptoms.