Opioid addiction is a chronic mental illness that manifests itself through several relapses and remissions throughout the course of an addict's life. Over the last few decades, opioid addiction has developed into a significant public health epidemic.
Classical molecular genetics research has limited the opioid receptor family down to three major subtypes: mu (μ), kappa (κ), and delta (δ) opioid receptors, which are encoded by the OPRM1, OPRD1, and OPRK1 genes. Individuals' opioid addiction is regulated by this OPRM1, OPRD1, and OPRK1 genes via a reward system route, including the dopaminergic system. Furthermore, when opioid ligands attach to these receptors, it produces euphoric and rewarding effects. Numerous research has been conducted on the single nucleotide variations (SNVs) of these genes in several ethnic groups. The majority of the studies had focused on the OPRM1 gene and its variants. Therefore, this article will summarize recent research on opioid receptor genetic variants associated with opioid addiction and emphasize the relevance and importance of investigating gene variants to ascertain genetic predisposition.
 

Keywords
OPRM1 , OPRD1 , OPRK1 , opioid addiction , rs1799971