A common polymorphism at the promoter region of serotonin transporter gene influences the reuptake of serotonin, thereby regulating its concentration in the synaptic cleft. Among individuals with one or more copies of the short allele at this location, serotonin reuptake is attenuated, resulting in increased availability of serotonin in the synapse and downregulation of post-synaptic binding sites (see Lesch et al., 1996). Allelic variation at 5HTTLPR has been implicated in alcohol use disorders relative to several domains, such as alcohol craving (Bleich et al., 2007) and relapse (Pinto et al., 2008); however, results have been mixed, with studies also failing to find an association between such variables and 5HTTLPR (e.g., Kohnke et al., 2006; Rasmussen et al., 2009). A more consistent finding in the literature has been the link between 5HTTLPR and alcohol dependence diagnosis. A meta-analytic review of 17 studies (including 3,489 alcohol dependent and 2,325 control participants) found support for a significant association between this polymorphism and diagnosis, with alcohol dependent participants being 18% more likely to possess at least 1 short (s) allele relative to control participants
