Epigenetics explains how nongenetic forces can alter generational phenotypes in a heritable manner.1 Certain addictions are not 100% heritable yet are still completely genetic in causation. An epigenetic effect via environmental exposure could play a role in addiction and should certainly be studied by behavioral geneticists. It's a valid alternative to psychobabble or conscious, willful decisions made by the addicts.
President and Founder, The National Association for the Advancement and Advocacy of Addicts (N4A)