Association of psychosis and movement disorders in the elderly.

There are a number of different relationships among aging, psychosis and movement disorders, most of which have been proposed to involve the neurotransmitter dopamine. Dopamine content and dopamine receptors have been shown to decrease with age, which may relate to the time of onset of different motor and psychotic disorders, as well as to the appearance of these disorders. For example, some so-called senile movement disorders, such as senile tremor and senile chorea, may relate to alterations in dopaminergic transmission with age, as might the general findings of increased slowing of movements and mildly increased rigidity with age, although it is not clear how common some of these changes are in the medically healthy elderly. Decrease in dopamine with age may also be associated with the findings that choreiform and psychotic disorders (which have been proposed to be related to excess dopaminergic activity) tend to predominate at younger ages, whereas parkinsonism is more common at later ages. Certain findings support this notion, such as the appearance of both dyskinesia and psychosis in patients treated with L-dopa, the finding that psychosis may be less common in patients with later-onset Huntington's disease, and the fact that neuroleptic-induced parkinsonism is often more severe in the elderly. However, the situation is more complicated than this, because there are a number of phenomena that do not fit the pattern, including the observation of an increased incidence of tardive dyskinesia in the elderly. Age-related changes in other transmitters are undoubtedly important in both movements disorders and psychosis, and even dopamine has been proposed to have both trophic and toxic properties over the aging process. In general, care is warranted in the use of any psychotropic medications in the elderly, because there can be widespread and often unpredictable effects of these drugs on both motor and mental function.