Investigations of the impact of measured genetic (i.e., DNA polymorphisms) influences on variation in the liability to drug addiction, in common with other complex disorders, have had limited success in explaining its total heritability, the proportion of the trait’s variance that is due to genetic factors. Replicable findings of a meaningful effect of genetic variants on disease risk or trajectory in drug addiction have been few (Bierut, 2011; Hartz & Bierut, 2010; Maher et al., 2011; Treutlein & Rietschel, 2011), both for specific drugs (Tobacco and Genetics Consortium, 2010; Xie et al., 2011) as well as for general liability to addiction (Maher et al., 2011; Schwantes-An et al., 2015).
