to be involved in addiction – e.g. the overabundance of cell adhesion molecules. These genes thus represent a vastly untapped resource for understanding addiction, and comorbid pleiotropically mediated psychiatric conditions, as well as for developing new treatments for these conditions. With regard to the fundamental question posed by the title of this article, although GWAS have generally failed to identify many of the genes that were previously identified by candidate gene studies, this is not to say that those findings are necessarily erroneous. It would appear that they may be involved in particular endophenotypes and particular populations, but at the same time these genes do not account for the majority of the genetic influence on addiction liability.
