A 3- or 4-repeat allele in the PDYN gene promoter, which was shown to produce significantly higher transcription activity of the PDYN gene than a 1- or 2-repeat allele, is a genetic risk factor for development of methamphetamine dependence (odds ratio: 1.83, 95% CI=1.24-2.68).
Because the polymorphism is located in the promoter region of the XBP-1 gene and affects transcription activity of the gene, it is unlikely that dysfunction of XBP-1 may induces susceptibility to methamphetamine dependence.
No polymorphism examined showed significant association with methamphetamine dependence, but two polymorphisms of DRD2 were associated with the clinical course and prognosis of methamphetamine psychosis.
A preliminary study: novelty seeking, frontal executive function, and dopamine receptor (D2) TaqI A gene polymorphism in patients with methamphetamine dependence.
Studies suggest that a functional polymorphism of the brain-derived neurotrophic factor gene (BDNFVal66Met) may contribute to methamphetamine dependence.
Our results indicated that the FAAHPro129Thr polymorphism showed a significant association with risk of methamphetamine dependence in the pooled subjects (odds ratio [OR]: 2.017; p < 0.001) and in the Malay (OR: 2.829; p < 0.001) and Chinese (OR: 3.685; p < 0.001) groups.
Our results showed that the distribution of the BDNFVal66Met genotype in Chinese subjects with methamphetamine dependence (OR=2.6, p=0.015) and methamphetamine psychosis (OR=0.2, p = 0.034) were significant compared with controls.
Because the Pro129Thr polymorphism reduces enzyme instability, it is unlikely that dysfunction of FAAH and enhanced endocannabinoid system induce susceptibility to either methamphetamine dependence/psychosis or schizophrenia.