DRD2 and alcohol dependence: Moreover, Blum and Noble’s group [15], also found evidence for carriers of the DRD2 A1 allele independent of alcoholism progressively reduced Bmax in subjects with A2/A2, A1/A2, and A1/A1 alleles, with subjects with A2/A2 having the highest mean values, and subjects with A1/A1, the lowest (up to 40% reduction) and confirmed by others [16].