The C-allele of the synonymous SNP rs2234918 (921T>C) in exon 3 was reported to be associated with heroin dependence in Germans (Mayer et al. 1997), but this result was not found in several other studies of this SNP in Germans (Franke et al. 1999), Han Chinese (Shi et al. 2002; Xu et al. 2002), EAs (Levran et al. 2008; Zhang et al. 2008), and AAs (Levran et al. 2009). No association of this SNP was found with AD in Taiwanese Han (Loh el et al. 2004) or with methamphetamine dependence/psychosis in Japanese (Kobayashi et al. 2006). A haplotype, which harbors the 80G-allele and the 921C-allele, was associated with OD, CD, and AD (Zhang et al. 2008).
