More broadly, this study also provides further support for an endophenotype approach in addiction genetics, which seeks to map the pathways from genetic risk to clinical risk by focusing on mechanistic intermediary processes that are more proximal to genetic variation (Gottesman and Gould, 2003; Ray et al., 2010b). Putative advantages of this approach are greater reliability across studies, the presence of larger effect size relationships, and improved insights into the neurobiological and psychological mechanisms of risk. These are clearly evident in the current study, which extends previous human laboratory findings in a modestly sized sample and suggests that the role of the OPRM1 A118G polymorphism in relation to AD is by way of its modulation of alcohol-induced reward.
