Here, we highlight two levels of analysis for differentially expressed genes (DEG): from three regions treated jointly (OFC, caudate, and nucleus accumbens), which we refer to as global analysis; and from each brain region considered separately, which we refer to as regional analysis. We first determined a parsimonious model for gene expression as a function of diagnosis (OCD versus unaffected comparison subjects) and other predictors. For the global analysis of DEG, predictors for the final model included diagnosis and brain region, as well as sex and pH as covariates (Table S1). It yielded 904 DEGs (FDR < 0.05; 471 were upregulated and 433 were downregulated). Predictors for the regional analyses were the same as the global analysis (e.g. diagnosis, with sex and pH as covariates), although effects were estimated by region. Between diagnostic groups, this analysis identified 29 (23 upregulated and 6 downregulated) and 216 (79 upregulated and 137 downregulated) DEG in the caudate and nucleus accumbens, respectively (FDR < 0.05; Fig. 1A; Table S2), and none for the OFC (Fig. S3). Examining overlap of DEG sets between global, caudate,
