The primary analysis examined the genetic correlation between the full PTSD and AD samples. Following the primary analysis, sex-stratified analyses were conducted using separate male (n ~ 85,000) and female (n ~ 86,000) summary statistics files for PTSD, as evidence suggests lower heritability (based on molecular and twin studies) for PTSD in males compared to females (Duncan, Cooper, & Shen, 2018). However, the combined sex AD sample was used for two reasons. First, meta-analyses of behavioral genetic studies on AUD has not found evidence of differential heritability for AUD in males compared to females (Verhulst, Neale, & Kendler, 2015). Second, the current sample size of the PGC AD data is modest and limited in power for sex-stratified analyses. As LDSC relies on molecular heritablity to estimate genetic correlation, in cases of too low heritability or too small N, models will not converge. Thus, similar to the flagship AD analyses from the PGC from which the summary statistics are drawn from for the present analyses (Walters et al., 2018), sex-statified analyses were not conducted for AD.
