This study analyzes the contribution of rare functional variants in OPRM1 to the risk for addiction. By studying variants with known function we can increase our understanding of addiction processes at the molecular level. rs62638690 has been shown to reduce the potency of MOR for opioids [31] and these data show a significant association of this SNP with drug addiction. A reduced sensitivity to opioids, therefore, may protect against addiction to illicit drugs. In order to confirm this nominally significant finding, additional genotyping in independent cohorts of individuals addicted to illicit drugs or prescription opioids is warranted.
