There is limited evidence that individual OPRK1 SNPs are associated with substance dependence; instead, many experiments measure linkage disequilibrium to consider SNPs in the larger context of how those SNPs may be linked in haplotype blocks. Although Zhang’s study found no significant differences in OPRK1 allele or genotype frequencies for individual SNPs, one specific OPRK1 haplotype, GGCTTCT, was significantly associated with alcohol dependence in European Americans [12]. While other findings may suggest that genetic variants in OPRK1 may be associated with alcohol dependence rather than opioid dependence [81].
