Four studies reported association of OPRK1 SNPs with OD. A study of eight SNPs in EA, AA and His subjects, reported association with the synonymous SNP rs1051660 (Yuferov et al. 2004). A study of an Italian sample replicated this finding (Gerra et al. 2007). A third study of 11 SNPs (not including SNP rs1051660) reported an association with the intronic SNP rs6473797 in EA subjects (Levran et al. 2008). No association with these 11 SNPs was detected in AA subjects (Levran et al. 2009).
