al. found rs2236861 to be significant associated only with non-dependent opioid use (case n = 163, control n = 153) but not opioid dependence (case n = 281) in a Dutch population [24], with no effect observed for either rs2236857 or rs3766951. The variation between European and Australian subjects or simply sample size might explain the divergent results in OPRD1. In total, the literature supports an effect of OPRD1 intron 1 genotype on opioid abuse or dependence risk; however, the identity of the causative single nucleotide polymorphism (SNP) and the specific nature of the effect still require additional research.
