GWAS have been overwhelmingly limited to individuals of European ancestries [50, 51]. Importantly, PGS derived from GWAS of one ancestry do not always transport into other ancestral populations [52, 53]. We therefore used PRS-CSx [54], a new method that combines information from well-powered GWAS (typically of European ancestries) and ancestrally matched GWAS to improve the predictive power of PGS in the African ancestry samples from Add Health and COGA. PRS-CSx integrates GWAS summary statistics across multiple input populations and employs a Bayesian approach to correct GWAS summary statistics for the non-independence of SNPs in linkage disequilibrium (LD) with one another [54]. For participants of European ancestries, we used the EUR-derived PRS-CSx results, while we used the EUR+ AFR meta-analyzed results for the African ancestry participants. See the supplementary information (section 5) for details.
