As most traits are affected by thousands of genetic variants, it follows that many of the underlying causal variants would be shared across traits (Visscher et al., 2017). Indeed, approximately 90% of variants are estimated to pleiotropic, which is to say that they are associated with multiple outcomes (Watanabe et al., 2019). Cross-disorder genomic efforts have sought to capitalize on this shared genetic architecture to identify variants that are pleiotropic across psychiatric disorders. Initial evidence indicated that rare CNVs were associated with a diverse range of disorders, including autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), and SCZ (Malhotra & Sebat, 2012). The Cross-Disorder Working Group of the Psychiatric Genomics Consortium (PGC) undertook their second major effort (CDG2) to meta-analyze a sample of 727,126 participants across 8 distinct psychiatric disorders (Lee et al., 2019). Results were indicative of 109 pleiotropic variants that were associated with at least two disorders, and 23 pleiotropic variants associated with four or more disorders. This included a variant (rs8084351) in the DCC gene associated with all 8 disorders and a variant (rs7193263) in the RBFOX1 gene
