['Several lines of evidence suggest that the dopaminergic nervous system contributes to methamphetamine (METH) dependence, and there is increasing evidence of antagonistic interactions between dopamine and adenosine receptors. We therefore hypothesized that variations in the A2A adenosine receptor (ADORA2A) gene modify genetic susceptibility to METH dependence/psychosis.', 'We first analyzed variations in the exons and exon-intron boundaries of the ADORA2A gene in METH dependent/psychotic patients. Then an association analysis between these single nucleotide polymorphisms and METH dependence/psychosis was performed using a total of 171 METH dependent/psychotic patients and 229 controls.', 'We found 6 variations, of which one single nucleotide polymorphism (SNP) was novel. Significant associations were observed between the allelic and genotypic frequencies of the Exon2+751 (rs5751876) SNP and METH dependence/psychosis. These associations were observed especially in females. In the clinical feature analyses, significant associations were observed between the SNP and the patient subgroup using METH alone (i.e., without concomitant use of other substances of abuse).'] Is the adenosine A2A receptor associated with methamphetamine dependence/psychosis in the Japanese population?