Morphologic and clinical differences between Early- and Late-onset obsessive-compulsive disorder: Voxel-based Morphometric study

•We found significantly increased left thalamic gray matter volume in OCD patients compared to healthy controls.•Aging-related volume loss in medial temporal regions was greater in late-onset OCD patients compared to early-onset OCD patients.•Early-onset OCD patients had poorer insight and greater severity of atypical OCD symptoms (symmetry, hoarding, others) than late-onset OCD patients.•Preserved volumes of medial temporal regions in early-onset OCD patients might be related to their poorer insight and lower emotional conflict compared to late-onset OCD patients.