committee approved all study procedures. Taking into account sex, age (dummy coded as quartiles), ancestry (represented by two principal components from a stratification analysis), and original study source (dummy coded to reflect the three primary studies) as covariates, we conducted association analyses in PLINK (Purcell et al., 2007), using DSM-IV alcohol dependence case-control status (ADx) and DSM-IV alcohol dependence symptom counts (ASx) as the dependent dichotomous and continuous phenotypic variables, respectively.
