We recognize the current study has some key differences from prior studies that warrant consideration. First, there are differences in sampling techniques. Prior studies that examined OPRM1 A118G × DAT1 VTNR interactions used a combination of prospective and retrospective genotyping. Subjects were selected and matched based on prospective OPRM1 *G genotype and demographic variables, then DAT1 VTNR were retrospectively genotyped. In the current study, all genotyping was completed retrospectively (after the sensitivity sessions) and no one was excluded from participation based on genotype results. The advantage of prospective genotyping is the ability to increase the sample size for minor alleles through oversampling, and balanced genotype groups for testing genetic associations. The disadvantage is that the sample is not random, which may bias sampling in unknown ways, particularly when balancing groups and examining epistatic interactions between different genes. Second, there are differences in route, alcohol-dosing procedures (single bolus vs. cumulative dosing), and maximum BAC reached. Some prior studies have used the intravenous route and peak BAC levels are often less than 0.08%. The current study used oral alcohol administration, as this
