Psychiatric side effects during the treatment of Parkinson's disease.

Dopaminergic agents including both levodopa and direct-acting agonists induce a variety psychiatric side-effects of which psychosis is the most significant. When this occurs early in the course of treatment, there is usually a history of prior psychotic illness. Chronic treatment can, however, elicit psychosis in individuals without such a history. The possible pathogenesis of this is reviewed.