In this study we examined whether laboratory-based findings regarding genetic influences on subjective responses to alcohol and urge to drink generalize to the natural environment. To this end, heavy drinkers, 61% of whom were alcohol dependent, used handheld electronic diaries to monitor drinking episodes for 5 consecutive days. Analyses revealed that carriers of the Asp40 allele of the OPRM1 gene reported greater feelings of vigor and less negative mood during drinking episodes, as compared to homozygotes for the Asn40 allele. This is generally consistent with the a-priori hypotheses and laboratory-based findings by Ray & Hutchison (2004, 2007). Interestingly, the interactions between OPRM1 genotype and eBAC suggested that as BAC increased, carriers of the Asp40 allele reported greater decreases in vigor and greater increases in negative mood, compared to homozygotes for the Asn40 allele. These results suggest that the greater stimulant effects of alcohol, reported by Asp40 carriers in their natural environment, may be dose-dependent and perhaps stronger at low levels of BAC.
