Meta-analysis of the symptom structure of obsessive-compulsive disorder

Abstract

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.

FIGURE 1

Factor Structure of the Yale-Brown Obsessive-Compulsive Scale Symptom Checklist Across the Lifespan^{a a} Symptom categories shaded in white are associated with the same factor across the lifespan. Symptom categories shaded in gray are associated with different factors in adults and children. Solid lines indicate that a symptom category is associated with a particular factor in adults. Dashed lines indicate that the symptom category is associated with a particular factor in children only. The hoarding and symmetry factors that are surrounded by a dashed box were collapsed into the same factor in some subgroup analyses, including when studies included non-English-speaking subjects or when ratings of symptom severity were used. The forbidden thoughts factor split into two separate factors in subgroup analyses involving non-English-speaking subjects and when only studies using item-level data were considered.