Levodopa-induced psychosis: a kindling phenomenon.

Of 88 patients with idiopathic Parkinson's disease, without prior psychotic symptoms, and without significant dementia, nearly half had experienced vivid dreams, hallucinations, illusions, and nonconfusional as well as confusional psychoses as side effects of chronic levodopa therapy within the previous year of treatment. It was found that 61.3% of all hallucinations were associated with preexistent or concurrent vivid dream phenomena, that all psychotic states were associated with preexistent or concurrent vivid dreams and/or hallucinations, and that nonconfusional psychotic states tended to become confusional. These findings raise the possibility that chronic levodopa therapy may result in dopaminergic kindling and support the hypothesis that chronic dopaminergic agonism may, via such a kindling mechanism, play a role in the development of some types of psychoses.