Several association studies of PDYN SNPs and different addictions were reported. Nine out of the eighteen PDYN SNPs tested in the COGA cohort (including rs1997794) were associated with AD (Xuei et al. 2006). The results were supported by haplotype analysis. SNP rs1997794 was reported to show no association with alcoholism in a small European sample (Geijer et al. 1997). Three SNPs were analyzed in Chinese subjects for association with OD (Clarke et al. 2009). No association in the overall sample, but an interaction between sex and genotype distribution was detected for rs1997794, in females. Also, SNP rs1022563 was associated with OD in females, suggesting a gender-specific role of PDYN. Association between a haplotype (SNPs rs1022563, rs2235749 and rs910080) and OD was reported in Han Chinese (Wei et al. 2011). Several studies of SNP rs35286281 (the 68-bp VNTR) did not produce consistent results for association with OD, CD or MD in several ethnic groups (Chen et al. 2002; Dahl et al. 2005; Nomura et al. 2006; Ray et al. 2005; Wei et al. 2011; Williams et al. 2007). An association between
