There was a significant main effect of DRD4 genotype on Urge to drink and a significant eBAC × DRD4 genotype interaction, after controlling for the model covariates. Overall, carriers of the DRD4-L allele reported significantly greater urge to drink following alcohol consumption than individuals who were homozygous for the DRD4-S allele. The BAC × DRD4 genotype interaction indicated that DRD4-S participants reported greater increases in urge to drink as BAC increased, as compared to DRD4-L individuals (Figure 3). As with the OPRM1 genotype analyses, described above, we added a baseline × genotype parameter to the DRD4 models shown in Table 3 and found no significant effects. Likewise, we added the eBAC × Gender term to each model and found that the results remained unchanged and that the eBAC × Gender was only significant (GEE parameter estimate = −20.29, SE = 8.37, z score = −2.42, p = < .05) when modeling Negative Mood. Specifically, males reported greater increases in negative mood at higher eBAC as compared to females.
