We used the gene expression patterns in the bulk tissue for each of the three brain regions to estimate the fractions of eight broad cell types: excitatory neurons, inhibitory interneurons, medium spiny neurons (a.k.a. spiny projection neurons), astrocytes, ependymal cells, immune cells, oligodendrocytes, and vascular cells (Table S4). After adjusting for covariates, OCD subjects were significantly different from unaffected comparison subjects for the representation of the following cell types in the global analysis: astrocytes (p = 0.005), vascular cells (p = 0.002), and medium spiny neurons (p = 0.009; Fig. 3A).The remaining cell types were not significantly different. Astrocyte cell fractions were larger in OCD subject samples, as were vascular cell fractions, whereas medium spiny neuron fractions were smaller in OCD samples (Fig. 3A). Regional analyses suggest smaller interneuron fractions in the OFC (Fig. 3B), smaller medium spiny neuron fractions in the caudate (Fig. 3C), smaller ependymal cell fractions in the nucleus accumbens (Fig. 3D), and a larger fraction of vascular cells in the OFC of OCD subjects compared to unaffected comparison subjects (Fig. 3B; Table S5). While regional results
