HLA genes have been reported to be involved in not only immune-related diseases9 but also several psychiatric disorders.10 We genotyped the HLA-B and HLA-DRB1 genes, and confirmed that the frequency of HLA-DRB1*13:02 was significantly higher in PD patients than in healthy individuals (case positivity: 18.1%; control positivity: 11.5%; P=2.62×10−5; odds ratio (OR)=1.70).11 Here, HLA-DRB1 is linked to psychiatric disorder.