Alcohol problems (AP) represent a significant public health concern with immense personal, social, and economic costs [1]. Twin and family studies have consistently suggested that alcohol-related phenotypes are genetically influenced, with heritability estimates for alcohol abuse and dependence estimated at ~50–60% [2–4]; estimates for other alcohol-related phenotypes are sometimes lower [5–7]. The heritability of alcohol use typically increases beyond adolescence [8, 9]. Alcohol-related phenotypes are complex genetic traits [10, 11], influenced by hundreds to thousands of genetic variants, each of small effect; these genetic factors are likely to interact with each other and the environment to impact risk, and to be heterogeneous [2], with phenotypically similar individuals harboring genetic risk variants with potentially little overlap.
