The results indicated that haloperidol-treated schizophrenia patients carrying neither HTR6 T nor SLC6A3 9R AIP-risk alleles (i.e., carriers of HTR6 C and SLC6A3 10R alleles) have significantly lower scores at ESRS subscale II for parkinsonism, ESRS-based tremor or hyperkinesia and ESRS subscales VI and VIII, in comparison to the carriers of either HTR6 T or SLC6A3 9R risk allele or carriers of both HTR6 T and SLC6A3 9R risk alleles (Table 5). This evidence concerns the gene HTR6 and Parkinson disease.