Chi-square and logistic regression analyses were used to test each alcohol-related symptom separately and ANOVA, t-test, and linear regression analyses were used to test the total symptom and SRE_5 scores. Analyses were first performed to assess whether ALDH2 genotype was significantly associated with alcohol-related symptoms. We then tested the combined effects of ALDH2 and ADH1B genotypes in multivariate regression analyses that included interaction terms. Based on the results of these analyses, we stratified the data by ALDH2 to test the effects of ADH1B. We also conducted all analyses with ethnicity included as a covariate in the models given the issue of population stratification and our previous findings of differences in level of response to alcohol across Chinese and Korean ethnic groups as measured by the total SRE, which includes assessment of current and heaviest drinking periods (Duranceaux et al., 2008); results were consistent with and without ethnicity included in the models so we present the data without ethnicity included (data available upon request).
