There are limitations to this study. The GABRA2 genotype groups are mixed with regard to recent drinking, family history, and race/ethnicity, and complete stratification along these parameters was not possible with the sample size. However, the subject samples with one or two copies of the risk allele did not differ significantly with regard to family history, drinking, and the presence of an alcohol use disorder. We nevertheless conducted several other analyses to further probe the potential influence of these variables. When using the presence of an alcohol use disorder as a covariate (a variable that was highly collinear with drinks/week, and a better model fit), the significance of the Genotype × Odor interactions was unchanged in the medial frontal ROIs that showed genotypic effects. The same was true when removing the all three subjects who tested positive for any illicit drug use.
