While molecular genetic correlations with AD and other phenotypes and PTSD and other phenotypes have been previously demonstrated, and one recent study examined the association between PTSD and alcohol use and did not find a significant genetic correlation (Wang et al., 2019), this is the first study to demonstrate a shared molecular genetic basis for AD and PTSD. Using recently published GWAS data from the PGC, a moderate, significant correlation was observed between AD and PTSD (r = .35). Our findings are consistent with evidence of shared latent genetic liability estimated from twin and family studies (Sartor et al., 2011, Xian et al., 2000). Notably, consistent with the original heritability analyses using the PGC PTSD and AD data (Nievergelt et al., 2019; Walters et al., 2018), our LDSC SNP-based heritability estimates were smaller than those reported from twin studies. This is expected and has been observed in the literature for many other phenotypes (Vischer, Brown, McCarthy, & Yang, 2012), purported due to factors such as many more variants still needing to be identified, requiring larger GWAS samples; rare variants and
