On the pathogenesis of abnormal involuntary movements in lithium-treated patients with major affective disorder.

Abnormal involuntary movements during long-term lithium treatment were investigated on two occasions, 7 years apart, in 37 outpatients with major affective disorder according to DSM-III. The patients had been on continuous lithium treatment for an average of 8.2 years when entering the study, and all had been exposed to neuroleptics. Psychiatric status and side effects were evaluated, and abnormal involuntary movements were assessed using the Abnormal Involuntary Movement Scale (AIMS). Signs of abnormal involuntary movements were age-dependent and seen in 8% of the patients at the initial investigation in 1980, and the proportion of affected individuals had increased by 16% by the end of the study in 1987. Women above the age of 50 (in which category the frequency of abnormal involuntary movements was 38%) were selected for further analysis. Severe abnormal involuntary movements in this category were associated with the early onset of affective illness, low body weight, the occurrence of dementia among first-degree relatives, and with high 12-h lithium levels.