Linkage disequilibrium and association with methamphetamine dependence/psychosis of mu-opioid receptor gene polymorphisms.

Several studies indicate that the mu-opioid receptor plays a role in addiction not only to opiate drugs but also to alcohol and non-opiate addictive drugs. Our studies aim to reveal the associations between gene polymorphisms and methamphetamine (MAP) dependence/psychosis. We newly identified several polymorphisms and four substantial linkage disequilibrium (LD) blocks in the mu-opioid receptor (OPRM1) gene. We found significant differences in both genotype and allele frequencies of the single-nucleotide polymorphism (SNP) IVS2+G691C between control (n=232) and MAP-dependent/psychotic patients (n=128). There was also a significant association between IVS2+G691C and patients with transient psychosis. These results suggest that the OPRM1 gene variations may be a factor in development and prognosis of MAP psychosis.