No association was found between individual BDNF, DAT, and COMT polymorphisms and MLIC in multinominal logistic regression analysis; meanwhile, genotypes combination of AG BDNF, AG DAT, and GG COMT was correlated with MLIC and genotypes combination of GG BDNF, AA DAT, and AA COMT with lack of MLIC in PD patients in OPLS analysis. Here, SLC6A3 is linked to Parkinson disease.