Objectives: To describe the incidence of tardive dyskinesia (TD) in the Yale TD Study and to identify demographic, treatment, and clinical risk factors for TD occurrence.
Design: An ongoing prospective cohort study in which subjects have been examined every 6 months since 1985.
Setting: The outpatient division of the Connecticut Mental Health Center in New Haven.
Subjects: Three hundred ninety-eight adult outpatients who had been maintained with neuroleptics for 3 months to 33 years at intake and who were free of persistent TD at intake with no history of persistent TD movements.
Outcome measure: New cases of persistent TD were defined as the presence of mild or more severe dyskinetic movements at two successive follow-up visits, using the Abnormal Involuntary Movement Scale.
Results: As of July 1, 1990, there were 62 new persistent cases of TD, yielding an average incidence rate of 0.053 per year and a 5-year risk of 20%. The TD rate was positively affected by age, being nonwhite, and neuroleptic dose, and it was inversely affected by years of previous exposure. Little or no effects were found for age at first neuroleptic exposure, type of neuroleptic, use of other psychiatric medications, and psychiatric diagnosis.
Conclusions: For outpatients maintained for many years with neuroleptics, dose should be minimized to reduce the risk of TD. This strategy does not appear to be negated by prescribing frequent changes in dosage. Although the TD rate is greatest during the first 5 years of neuroleptic treatment, new persistent cases continue to occur many years after first exposure.