We reported lower cortical thickness of numerous regions throughout the brain of medicated adult OCD patients. These medication effects partially overlap with prior research (12). Although these findings need to be interpreted with caution, it has been suggested that antidepressants might modulate plasticity in the brain (39). Additionally, post-hoc analyses suggest that these medication effects are strongest in those patients taking antidepressants with adjuvant antipsychotics (Supplementary Tables S36a–c and Supplementary Info SI4). Alternatively, those patients taking medication could represent a more clinically severe cohort that manifests these morphometric abnormalities. Results may have been confounded by a higher illness severity and a higher percentage of comorbid depression of the medicated adult OCD group (Supplementary Table S35). However, results of post-hoc analyses comparing the most severe (YBOCS>30) unmedicated OCD patients to controls did not resemble the same pattern of medication effects. Nevertheless, the cortical abnormalities in currently medicated OCD patients could reflect persistent abnormalities related to increased OCD severity before treatment. In addition, medication effects persisted after adding a covariate correcting for illness severity (data not shown). The lack of association between
