It is an exciting time to be able to summarize and review the rapidly-emerging data on the complex genetics of human addiction vulnerability and of related phenotypes. Genome wide association results for dependence on several different classes of addictive substances converge with each other in striking fashion that is highly unlikely to be due to chance. Studies of dependence phenotypes in samples of individuals from several different racial and ethnic backgrounds support the idea that many of the allelic variants that predispose to these common disorders are so evolutionarily old that they are present in members of each major current human population. These data, combined with the varying results from linkage-based studies, fit a genetic architecture for addiction that is based on polygenic contributions from common allelic variants. Such a genetic architecture is quite consistent with data from family, adoption and twin classical genetic studies.
