Contrary to the hypotheses and some previous findings, OPRM1 did not relate to subjective effects during alcohol self-administration. Initial evidence for greater hedonic responses among 118G carriers came from studies using experimenter-determined infusion profiles designed to capture three BrAC levels on the ascending limb (Ray and Hutchison, 2004, 2007), whereas the current study included only one subjective assessment at which BrAC was standardized. At this point the target BrAC was relatively low (30mg%), and subsequent assessments occurred in the context of varying aBAC levels. Other laboratory studies examining OPRM1 and subjective responses have also found results that diverged from early reports (Anton et al., 2012; McGeary et al., 2006), perhaps reflecting differences in laboratory paradigms. Consistent with the study hypotheses we observed significant associations of subjective responses and CASE outcomes, adding to previous evidence that subjective responses relate to intravenous self-administration (Zimmermann et al., 2009). However, the nature of these associations differed based on measurement scales: when considering a baseline measure of alcohol sensitivity, participants who reported needing more drinks to achieve stimulant effects showed significantly higher self-administration. During self-administration,
