The essential features of addiction are loss of control over consumption, obsessive thoughts about the drug, and continuation of use despite knowledge of negative health and social consequences [3, 4]. It has been established, largely through twin and adoption studies, that the heritability (the genetic component of the variance) of all addictive substances lies between 40% and 70%, the heritability of alcoholism is about 50%, and that of cocaine and opiate addiction is about 60% to 70% [5]. Therefore, genetic and environmental risk factors for the development of addictive disorders are equally important. Moreover, alcoholism is a heterogeneous disorder. A latent class analysis of the NESARC dataset identified five homogeneous subtypes distinguishable by family history, age at AD onset, endorsement of DSM-IV AUD criteria, and comorbidity [6]. These subtypes are likely to differ in genetic and environmental risk factors.
