Tardive dyskinesia and ethnicity: review of the literature.

Tardive dyskinesia (TD) is a side effect of long-term neuroleptic administration. The wide variation of 2 to 51% in its reported prevalence can be attributed to the varied definitions of TD, the use of different methods of assessment, and the lack of control of independent variables. Why only certain patients develop this side effect is an intriguing question. The occurrence of TD in family members and in those persons with a family history of Parkinson's disease (PD) is suggestive of genetic vulnerability. Further support for a genetic predisposition comes from the fact that only certain strains of monkeys, such as the Cebus apella strain, have a higher propensity to develop TD than others, such as the Macaca sepciosa strain. If genetic factors play a significant role in the development of TD, then, genetically diverse ethnic groups may have a different propensity for the development of TD. One method of evaluating such a possibility is to compare its prevalence in different countries. The current literature on ethnic differences in the prevalence rates of TD is reviewed. This area of study needs further rigorous investigation.