by a quantitative scale. Controls were defined as individuals who had been exposed to alcohol (and possibly to other drugs) at sufficient amounts for a sufficient time, but had never become addicted to alcohol or other illicit substances (lifetime diagnoses). This criterion for controls took into account the confounding effects from an environmental factor, i.e., drinking. In contrast to general controls who had never used substances, our controls reduced the potential false negative rates, because a proportion of general controls might still have a risk to develop to alcohol dependence when drinking. Additionally, controls were also screened to exclude individuals with major axis I disorders, including schizophrenia, mood disorders, and anxiety disorders. More detailed demographic information is available in Materials and Methods S1 or elsewhere [3], [5], [6], [9]. AA and EA samples were genotyped on the Illumina Human 1 M beadchip and Australian sample was genotyped on the Illumina CNV370v1 beadchip.
