More recent evidence suggests that genetic variants in the ADHIA,
ADHIB, ADHI C ADHS, ADH6, and ADH7 genes are associated with illicit drug dependence and that this association is not purely attributable to co-morbid alcohol dependence (Luo et al.
Moreover, two of the seven ADH genes, called
ADHIB and ADH1C, are polymorphic--that is, they exist in more than one variant (i.