Thus, for both the OPRM1 and DRD4 polymorphisms under study, participants’ subjective responses to alcohol were more strongly dose-dependent for carriers of the minor alleles (i.e., Asp40 and DRD4-L), such that these individuals reported overall greater levels of vigor, lower levels of negative mood (OPRM1 Asp40), and stronger urge to drink (DRD4-L) across drinking episodes. Nevertheless, at higher levels of eBAC these individuals reported greater decreases in vigor, increases in negative mood, and lower increases in urge to drink, respectively. Further investigation on the nature of the OPRM1 (and DRD4 VNTR) by BAC interactions seems warranted in order to more fully elucidate the effects of these polymorphisms on subjective responses to alcohol and drinking behavior per se. This is particularly important considering that BAC was estimated and not directly measured in this study and that not all individuals reported drinking episodes at the various possible levels of BAC.
