Tardive dyskinesia: a 3-year follow-up study.

A prospective study of tardive dyskinesia was carried out to gain information regarding the natural history of the condition and to identify risk factors. Out of an original cohort of 182 psychiatric patients receiving maintenance antipsychotic drugs 99 were available for reassessment after 3 years. In this follow-up group the point prevalence of oro-facial dyskinesia increased from 39% to 47% over the 3-year period. Twenty-two patients developed the disorder, while remission occurred in 14 others. Risk factors predicting the presence of oro-facial dyskinesia at follow-up included being over 50 years of age and the presence of akathisia. There was no convincing association between the duration of antipsychotic drug treatment and the presence or severity of oro-facial dyskinesia. Patients receiving over 1000 mg chlorpromazine equivalents of antipsychotic drug per day were unlikely to have the condition. The amount of purposeless trunk and limb movement present proved to be a relatively stable phenomenon, showing only a slight increase with age and no change over the follow-up period. The implications of these findings are discussed, with particular consideration being given to the effects of loss of patients to follow-up.