Fourth, we found extensive evidence that neurodevelopmental effects underlie the cross-disorder genetics of mental illness. In addition to DCC, a link between pleiotropy and genetic effects on neurodevelopment was also seen for other top loci in our analysis, including RBFOX1, BRAF, and KDM7A, all of which have been shown in prior research to influence aspects of nervous system development. Gene enrichment analyses showed that pleiotropic loci were distinguished from disorder-specific loci by their involvement in neurodevelopmental pathways including neurogenesis, regulation of nervous system development, and neuron differentiation. These results are consistent with those of a smaller recent analysis in the population-based Danish iPSYCH cohort (comprising 46,008 cases and 19,526 controls across six neuropsychiatric disorders) (Schork et al., 2019). In that analysis, consistent with the present findings, functional genomic characterization of cross-disorder loci implicated fetal neurodevelopmental processes, with greater prenatal than postnatal expression. In addition, SORCS3 emerged as a genome-wide significant cross-disorder locus in both studies. However, other specific loci, cell types, and pathways implicated in the iPSYCH analysis differed from those identified in our study. In supplementary analyses, we did
