The prevalence of abnormal involuntary movements among chronic schizophrenics.

In an international survey of chronic schizophrenia, data were collected on the Abnormal Involuntary Movements Scale (AIMS) to ascertain the prevalence of tardive dyskinesia. Abnormal movements were found to present in 28% of the sample of 739 patients. Using the more stringent Research Criteria for Tardive Dyskinesia (RD-TD) the prevalence rate was found to be 13.6%. Statistically significant differences were obtained between patients meeting RD-TD criteria and patients with abnormal movement who did not meet RD-TD criteria on total score, global severity, degree of incapacity and patient awareness--all reflecting greater severity in the RD-TD group. A much lower rate of moderate/severe tardive dyskinesia than that reported in the literature was obtained in this sample. Using the Leonhard classification of chronic schizophrenia, it was found that patients with prominent negative symptomatology had a high prevalence of tardive dyskinesia--confirming the previous reported relationship between these variables. Prevalence differences, possibly related to specific psychopathological syndromes, were also obtained.