Alcohol misuse (i.e., risky drinking and alcohol use disorder) is a top public health problem worldwide (World Health Organization, 2014), and reflects a complex interplay of genetic and environmental influences across development (Pagan et al., 2006). Twin and adoption studies have been critical in demonstrating that genetic influences account for roughly half of the variation in the risk for alcohol use disorder (Verhulst et al., 2015) and other alcohol use behaviors (Dick et al., 2011). Translating findings from family-based research designs of unmeasured genetic variance (i.e., inferred based on resemblance among different types of relatives) into a measured genetic framework to identify the specific variants associated with alcohol outcomes has been challenging (Hart and Kranzler, 2015). Although a few individually important genes and genetic variants have been identified, results from genome-wide association studies (GWAS) of alcohol use disorder underscore its highly polygenic nature (Yang et al., 2014, Hart and Kranzler, 2015, Mbarek et al., 2015). This high level of polygenicity is consistent with emerging findings from GWAS of psychiatric disorders more broadly (Geschwind and Flint, 2015), as well as findings that psychiatric conditions also share much of their polygenic underpinnings (Anttila et al., available online April 2016).
