Second, we reanalyzed these GWAS datasets using our previous single-cell RNA-seq dataset (24 cell types from the neocortex, hippocampus, striatum, hypothalamus midbrain, and specific enrichments for oligodendrocytes, serotonergic neurons, dopaminergic neurons and cortical parvalbuminergic interneurons, 9970 single cells; Figure 3B, S17 and Table S8). We again found strong associations of pyramidal neurons from the somatosensory cortex, pyramidal neurons from the CA1 region of the hippocampus (both corresponding to telencephalon projecting excitatory neurons in our main dataset), and medium spiny neurons from the striatum (corresponding to telencephalon projecting inhibitory neurons) with psychiatric and cognitive traits. MDD and autism were most associated with neuroblasts, while intracranial volume was most associated with neural progenitors (suggesting that drivers of intracranial volume are cell types implicated in increasing cell mass). The association of dopaminergic adult neurons with Parkinson’s disease was significant at a nominal level using LDSC (P=0.01), while oligodendrocytes did not replicate in this dataset, perhaps because they were not sampled from the regions affected by the disorder (i.e. spinal cord, pons, medulla or midbrain). A within-neuron analysis again found that projecting excitatory (i.e.
