Support for an association of the C939T polymorphism in the human DRD2 gene with tardive dyskinesia in schizophrenia

Tardive dyskinesia (TD) is a movement disorder linked to long-term treatment with antipsychotic drugs. Since all typical antipsychotics are dopamine D2 receptor (DRD2) antagonists, it has been suggested that genetic variations in the human DRD2 gene might be associated with TD. Recently, one coding-synonymous polymorphism, C939T (rs6275) in exon 7 of the DRD2 gene, has been associated with TD in a Caucasian group. In the present study, we investigated whether this polymorphism is also associated with TD in a Chinese population. Three hundred and one patients (TD/non-TD = 174/127) with schizophrenia being treated with long-term typical antipsychotics were enrolled in this study. There was no significant difference in the proportion of male and female participants or smokers and non-smokers, and no difference in the mean age, chlorpromazine equivalent doses or years of antipsychotic exposure. The C939T genotype and allele distribution differed significantly between the TD and non-TD groups (p = 0.003 and p = 0.002, respectively). Patients homozygous for the 939T allele and the heterozygous carriers of CT had an increased risk of TD compared with 939C homozygotes (OR_TT = 3.59, 95% CI = 1.71-7.53, p = 0.001; OR_CT = 2.37, 95% CI = 1.21-4.66, p = 0.012). Therefore, our findings suggest that, similar to the findings in Caucasians, the C939T polymorphism in the DRD2 gene is associated with TD in a Chinese population. However, given the study's small sample size, the findings should be regarded cautiously. Further studies with larger sample sizes will be necessary before any firm conclusions can be drawn.