The samples included in this study for SRE scores were also utilized in a previous GWAS (Lai, Wetherill, Kapoor, et al., 2019). In that study, no variant was genome-wide significant in meta-analysis of COGA and NIAAA cohorts, and that null finding was attributed to the relatively small sample size (N=1,546)) (Lai, Wetherill, Kapoor, et al., 2019). In contrast, the current admixture mapping approach successfully identified a region on chromosome 4. Consistent with other studies, these findings corroborate the importance of applying admixture mapping for variant discovery in recently admixed samples, including those that might have been underpowered for detection using standard approaches. In that previous GWAS study of SRE, one variant (rs4770359, P-value=2.92E-08, Beta=0.16; SE=0.03; effective allele: A) on chromosome 13 was genome-wide significant for SRE-5 in COGA only but not replicated in the NIAAA cohort (P-value=0.82), and meta-analysis has a P-value of 6.33E-08 (Lai, Wetherill, Kapoor, et al., 2019). In the current admixture mapping analysis, this region was marginally associated with SRE-5 (P-value=0.08), with African ancestry increasing SRE-5 scores, which is in agreement with the prior GWAS result. This
