Most of these studies were predominantly based on volumetric measures using voxel-based morphometry (VBM). Volumetric measures, however, depend on a combination of changes in gray matter thickness and surface area (17). Fewer studies have used surface-based methods to generate detailed maps of cortical thickness and surface area. These measures represent distinct features of cortical morphometry that are somewhat genetically independent and are driven by different neurobiological processes (18). Studying these properties independently will make it easier to interpret the cortical abnormalities reported in OCD in the context of the postulated neurodevelopmental basis for OCD (19) (Supplementary Information SI1).
