Finally, we compared the association between the EXT and ALCP-specific PGSs with an alcohol use index (AUI) [28] across time using a linear growth model [29] in Add Health. This composite index included five alcohol phenotypes ranging from normative to problematic use, scaled to a value of 0 to 10 [28] and is well suited to capture the developmentally contingent definition of substance “misuse” (e.g., early life initiation, drinking to intoxication in adolescence, developing problems in adulthood). Detailed descriptions of the holdout samples, phenotypes, and analyses are presented in Supplementary Note 4.
