In the search for potential genetic risk factors for substance dependence, much work has focused on genes involved in neurotransmitter regulation. For example, associations with alcohol dependence have been established for the dopamine transporter gene (Kohnke et al., 2005), the D2 dopamine receptor gene (Smith et al., 2008), and the monoamine oxidase A gene (Contini et al., 2006). Given the relevance of serotonin to alcohol use and abuse (see Tabakoff and Hoffman, 2004), the serotonin transporter gene has also received substantial research attention.
