developing drug dependence (Schinka et al., 2002). Alternatively, in drug-dependent individuals in Eastern European and Russian populations, the G118 allele occurred more frequently (Zhang et al., 2006a). In addition, several studies using linkage disequilibrium or haplotype analysis (Crowley et al., 2003; Luo et al., 2003), case- or family-controlled studies (Franke et al., 2001; Gelernter et al., 1999; Xuei et al., 2007), or meta-analyses of past studies (Arias et al., 2006) failed to detect a significant involvement of A118G in drug dependence.
