Importantly, we note that this pattern of results was driven by participants of EA, and that one contrasting finding was observed among AA participants. It is important to interpret the AA findings (i.e. those whose h2SNP Z-scores were less than 4) with caution, as these heritabilities may be less precise (Bulik-Sullivan et al., 2015a). For AA analyses, the AFR UKB pan-ancestry LD scores were used, and it should be noted that more research is needed to clarify the extent of bias resulting from using admixed ancestry reference panels (Bulik-Sullivan et al., 2015a; Bulik-Sullivan et al., 2015b). Other methods such as cov-LDSC (Luo et al., 2021), which can construct cohort-specific LD reference panel increase accuracy, but requires access to measured genotypes, which are largely unavailable for the samples in the current study. The field is in critical need of large-scale diverse ancestry cohorts and the corresponding methods development to robustly analyze these data (Peterson, 2021). Increasing ancestral diversity in large genetic studies will enable improved understanding of the epidemiology of PTSD, alcohol use behaviors, and their comorbidity.
