Tardive dystonia. Prevalence, risk factors, and comparison with tardive dyskinesia in a population of 200 acute psychiatric inpatients.

In a population of 200 consecutive inpatients with a history of at least 3 months' total cumulative neuroleptic exposure, the prevalence of tardive dystonia (TDt) was 4%, higher than previously reported. The prevalence of tardive dyskinesia (TDk) was 22%. Patients with TDt did not differ in demographic or clinical variables from nondyskinetic patients. In comparison with patients with TDk, patients with TDt were significantly younger, had a more severe movement disorder, and had received neuroleptics for the first time fewer years before. Patients with TDk were significantly older than patients without tardive disorders, both when they were examined and when they had started their first neuroleptic treatment. Furthermore, they had started their first neuroleptic treatment more years before. These results support the distinction between TDt and TDk, and suggest that the previously reported prevalence of TDt might have been underestimated.