DRD2 and movement disorder: In a population with chronic mental illness, various SNPs in 10 candidate genes (PPP1R1B, BDNF, DRD3, DRD2, HTR2A, HTR2C, COMT, MnSOD, CYP1A2, and RGS2) reached nominally significant (p≤0.05) associations with drug-induced movement disorder.