Anterior insular volume is larger in patients with obsessive-compulsive disorder.

There has been increasing evidence indicating gray matter abnormalities in patients with obsessive-compulsive disorder (OCD). Several voxel-based morphometry (VBM) studies have reported volume changes in the insular cortex. Although there are distinct differences in the connectivity and functions in the anterior and posterior insular cortices, these two regions have never been distinguished in previous VBM studies. In this study, we adopted a region of interest (ROI) method to measure insular volume separately. We investigated insular volume in 32 drug-free patients with OCD and in 34 healthy controls using magnetic resonance imaging (MRI). Repeated measures multivariate analysis of covariance (MANCOVA) was conducted to examine the difference between the patients and the controls. Compared with the healthy controls, the patients had a significantly larger gray matter volume in the anterior insular cortex bilaterally (post hoc test, p=0.036; left, p=0.047; right). This is the first volumetric MRI study to separately investigate the anterior and posterior insular cortex volumes in non-medicated patients with OCD. The results suggest that the anterior insular cortex may be related to the pathophysiology of OCD.