Epidemiological aspects of tardive dyskinesia.

Although there continues to be some debate as to the extent to which neuroleptic drug treatment is either necessary or sufficient to produce abnormal involuntary movements in various psychiatric populations, the consensus at present is that neuroleptics do play a major role in producing, precipitating or evoking abnormal involuntary movements. No doubt a variety of other factors play a critical role in predisposing particular individuals to the development of the condition. Numerous prevalence surveys have been conducted and extensively reviewed. In general, prevalence surveys have helped to identify populations at particular risk, to suggest factors which contribute to risk and to establish the overall scope of the problem. The strategy of estimating prevalence in a specific population has limitations, however, and further advances in our understanding of tardive dyskinesia (TD) will require a different type of methodology. Important progress has been made in the last several years involving prospective studies of TD development. Current estimates of incidence suggest that TD develops in about 5% of patients with each year of cumulative neuroleptic exposure. These data are derived from relatively young patients (average age 28); the incidence in older individuals is likely to be higher. Further data on the epidemiology of TD will be presented.