Next, we examined neuronal cell type-specific gene expression in ADHD using two approaches. First, we tested for enrichment of variants located in cell-specific epigenomic peaks by intersecting our genetic associations with data from two recent catalogs of the human epigenome that profile major human body cell types31 as well as brain-specific cell types32. Here we found enrichment for genes expressed in major brain neuronal cell types, including both excitatory and inhibitory neurons (Supplementary Fig. 9). Second, we performed cell type-specific analyses in FUMA33 based on single cell RNA-sequencing data. This revealed a significant association (P = 0.005) between ADHD-associated genes and genes expressed in dopaminergic midbrain neurons (Linnarsson midbrain data34; Supplementary Fig. 10 and Supplementary Table 15).
