Context: Whether obsessive-compulsive disorder (OCD) is adequately classified as an anxiety disorder is a matter of considerable debate.
Objectives: To quantitatively compare structural brain changes in OCD and other anxiety disorders using novel voxel-based meta-analytical methods and to generate an online database to facilitate replication and further analyses by other researchers.
Data sources: The PubMed, ScienceDirect, and Scopus databases were searched between 2001 (the date of the first voxel-based morphometry study in any anxiety disorder) and 2009. All voxel-based morphometry studies comparing patients with any anxiety disorder and healthy controls were retrieved. Manual searches were also conducted. Authors were contacted soliciting additional data.
Study selection: Thirty-seven data sets were identified, of which 26 (including 639 patients with anxiety disorders and 737 healthy controls) met inclusion criteria.
Data extraction: Coordinates were extracted from clusters of significant gray matter difference between patients and controls. Demographic, clinical, and methodological variables were extracted from each study or obtained from the authors.
Data synthesis: Patients with anxiety disorders (including OCD) showed decreased bilateral gray matter volumes in the dorsomedial frontal/anterior cingulate gyri. Individuals with OCD had increased bilateral gray matter volumes (vs healthy controls and vs individuals with other anxiety disorders) in the lenticular/caudate nuclei, while patients with other anxiety disorders (mainly panic and posttraumatic stress disorders) had decreased gray matter volumes in the left lenticular nucleus. The findings remained largely unchanged in quartile and jackknife sensitivity analyses. Controlling for potential confounders such as age or antidepressant medication had little impact on the results.
Conclusions: The meta-analysis consistently revealed common as well as distinct neural substrates in OCD and other anxiety disorders. These results have implications for the current debate surrounding the classification of OCD in the DSM-V.