To the Editor.—
The reported prevalence of tardive dyskinesia (TD)—abnormal involuntary movements that develop during chronic treatment with neuroleptic drugs—varies widely, and the data on risk factors, especially among younger patients, are contradictory.1Though these drugs themselves are known to suppress TD, the current doses of neuroleptics have received relatively little attention in the actual epidemiological studies. The results of our recent study2 illustrate how this factor may affect the findings.
Patients and Methods.—
The sample consisted of 68 patients with schizophrenic or schizoaffective illness who were from 22 to 59 years of age (73% were under 40 years of age). All were receiving long-term treatment with neuroleptic drugs, most of them with fluphenazine decanoate or flupentixol decanoate. The current dose, expressed in equivalents of fluphenazine decanoate, ranged from 4.1 to 250 mg/week, and in all but two subjects it was kept constant for at least two months