Although, robust and replicated variant level associations have yet to be discovered for alcohol related measures, most GWAS have supported the hypothesis that these phenotypes are classic quantitative genetic traits, influenced by many variants (hundreds to thousands) of individual small effect. Methods that examine the aggregate effects of common variants represent an important complement to analyses based on single markers (e.g., primary GWAS results) and support the results from twin and family studies. Heritabilities based on common markers using unrelated individuals have been reported including an alcohol problems score in Dutch adults (0.33; Mbarek et al., 2015), and maximum drinks in 24 h and alcohol use disorder (AUD) (0.32 and 0.34, respectively; Kos et al., 2014) in a modestly sized sample of Mexican-American adults. However, in a UK sample of emerging adults, a heritability estimate of 0.05 for alcohol problems was non-significant (Edwards et al., 2015).
