linkage disequilibrium with it (Levran et al., 2008). In a meta-analysis of 22 studies including 8000 subjects divided by ethnicity and substance dependence type, the 118A>G polymorphism did not appear to affect the risk for substance dependence in general (Arias et al., 2006). Another meta-analysis, focusing strictly on opioid dependence, also failed to find evidence for association with the 118A>G polymorphism, in 21 case-control studies representing 1742 opioid dependent cases and 2585 control subjects from European, African, Asian and Native American ancestry (Glatt et al., 2007).
