Drug addiction is an important social problem in many countries. Genetic and environmental factors contribute to the predisposition of drug addiction. Genetic variations at the μ opioid receptor (OPRM1) gene locus have been associated with opiate addiction. The present study aims to delineate the frequency of A118G allele of OPRM1 among Malaysian subjects. The frequency of A allele and G allele were 51% and 49%, respectively for addicts and about 73% and 27% respectively for healthy volunteers. The frequency of G allele was 1.77-fold higher in addicts by odds ratio calculation at 95% Cl, which indicate the G allele to be strongly associated with addiction X(2) = 15.31,P < 0.0001; odds ratio 2.51; 95% Cl (1.575-3.994), compared to healthy volunteers. A significant association was observed between A118G polymorphism in μ opioid receptor gene and drug addiction.
A majority of studies have shown a link between the common functional rs6265 polymorphism of the BDNF gene and susceptibility to drug dependence. However, the pattern of results is inconsistent. To precisely evaluate this association, a systematic review and meta-analysis of previous case-control reports was conducted. Data from 20 studies containing 9419 participants (4665 cases and 4754 controls) conducted between 2004 and 2013 restricted to alcohol, nicotine, heroin, substance and methamphetamine dependency were meta-analyzed. Following quality control of the results, a significant association between C allele and methamphetamine dependence remained in south Asian subjects (p = 0.004). Similar results were detected in south Asian subjects for methamphetamine dependence and in Chinese subjects for heroin dependence under an autosomal codominant genotype model (TT vs CC, p = 0.005 and p = 0.0004, respectively). In conclusion, the rs6265 polymorphism may be a risk factor for methamphetamine dependence in south Asian subjects or for heroin dependence in Chinese subjects.
FAAH is a membrane enzyme that terminates the activity of a large class of endogenous signaling lipids. Recent studies suggest that the FAAH Pro129Thr polymorphism is a common mutation in the FAAH gene that is significantly associated with drug-addictive traits. This study investigated the association of the Pro129Thr polymorphism of the FAAH gene with methamphetamine dependence, methamphetamine-induced psychosis, manic episodes and panic disorder in a Malaysian population.