The point prevalence of tardive dyskinesia (TD) as assessed by means of the Simpson rating scale was determined for 14 psychiatric wards with 347 patients (213 and 134 female) at the time of the study. TD was found to occur in 17.3 per cent of the patients, the prevalence being significantly higher in female than in male patients. The frequency of TD increases with age.
A random group of TD patients was matched with a group of patients without TD and the total medication for both groups was calculated. No differences were found as concerns total amount of high or low dosage neuroleptics, or anticholinergic drugs, for the two groups. However, significantly more TD patients than controls had received dosage neuroleptics, or anticholinergic drugs for the two groups. However significantly more TD patients than controls had received anticholinergic drugs.
There was no significant relationship between severity of TD: age, duration of treatment, total amount of high or low dosage neuroleptics. On the other hand a significant relationship was found between severity of TD and amount of anticholinergic drugs. Significantly more patients in the TD-group than in the control group had a past history which might suggest possible brain damage prior to the neuroleptic medication.