We found that while ADH1B-rs1229984 and ADH1C-rs698 were correlated (r2=0.32; D′=0.44), they did not represent a single signal; each variant contributed to risk independently. Due to the unique haplotype structure in this population, we were able to directly examine the joint effects of ADH1B-rs1229984 and ADH1C-rs698 on alcohol phenotypes by identifying ADH1B-rs1229984 and ADH1C-rs698 diplotypes with certainty, categorizing them into three risk groups, and testing the specific combinations of risk variants for alcohol phenotypes. For both the binary and count measures of AD and AUD, significant differences were observed across each of the three diplotype risk groups, indicating that both SNPs play a role in these outcomes. These results agree with the single SNP analyses, which indicated that both ADH1B-rs1229984 and ADH1C-rs698 were associated with AUDs, while ADH1C-rs698 was not significantly associated with consumption. While the diplotypes explained roughly the same amount of the variance in these traits (e.g. ∼19% of the variance in AD) as either ADH1B-rs1229984 (∼18% of the variance in AD) or ADH1C-rs698 (∼17% of the variance in AD) individually, considering these SNPs together provides a model
