The discovery sample was genome-wide SNP data on 1788 regular drinkers (defined below) from 118 large European-American families densely affected with alcoholism;15 subjects from that study who were not regular drinkers were excluded. Ascertainment was based on a proband in treatment for alcohol dependence who had at least two first-degree relatives affected by alcohol dependence. Of these subjects, 685 met criteria for DSM-IV alcohol dependence (mean age of onset 22.5 years). A genome-wide Cox proportional hazards regression model was used to test the association between age at onset of AD and 4 058 415 imputed SNPs with minor allele frequency ⩾5%.15 A robust sandwich variance estimators approach was used to account for the familial correlation among observations (https://cran.r-project.org/web/packages/survival/survival.pdf).
