In summary, we provide modest evidence for the association between DRD2/ANKK1 and alcohol use/problems. In capturing the genetic heterogeneity across alcohol measures in genetic factor scores, we found association between DRD2/ANKK1 SNPs with both regular and problematic drinking. It should be noted that the β values associated with each significant DRD2/ANKK1 SNP range from 0.001–1.30, indicating that a very small portion of the variation in alcohol behavior is accounted for by DRD2/ANKK1 SNPs. In this study, we also demonstrated how to maximize the information obtained by twin analyses and molecular analyses within the same sample. By reducing the genetic heterogeneity inherent in the alcohol phenotype and the number of phenotypes analyzed, we detect a genetic association between DRD2/ANKK1 and alcohol use and problems, which would have been deemed nonsignificant had we not incorporated the genetic architecture across the traits.
