An exploratory factor analysis conducted in Mplus (Muthen and Muthen 2007) revealed a single strong AD factor with loadings ≥ +0.84 for all seven items. A confirmatory single factor analysis yielded excellent values for CFI (0.976) and TLI (0.984) and acceptable values for RMSEA (0.086). All items loaded very strongly on the common factor with the two highest assessing alcohol-related interference (+0.97) and loss of control (+0.93) while the two lowest (both +0.83) evaluating tolerance and use of alcohol despite knowledge of harm. These factor scores were then regressed onto the covariates of age, sex, and race (i.e., EA versus AA) and the residuals, for GWAS analysis. The distribution of this score is seen in Figure 1.
