Tardive dyskinesia: characterization and prevalence in a statewide system.

The prevalence of tardive dyskinesia in a state-wide mental hospital system was assessed using a new quantitative rating scale and related to demographic, medication, and medical history variables. Twenty-six percent of patients had definite signs of tardive dyskinesia, about 12% moderately severe dyskinesia, and 40% exhibited at least some minimal symptoms. Tardive dyskinesia significantly increased with age, and females had a slightly but significantly greater prevalence rate than males. There was no difference in dyskinesia prevalence between patients on or off neuroleptics at time of rating, but patients on multiple neuroleptic drugs had higher prevalence of moderately severe dyskinesia.