Neuropsychological and psychiatric side effects in the treatment of Parkinson's disease.

All medications currently used to treat Parkinson's disease carry some risk of causing confusion, hallucinations, or disruption of such higher-order mental operations as problem-solving and learning. Although the elderly demented patient is at greatest risk, such complications have also been noted during treatment of younger patients. Treatment with anticholinergics may lead to a confusional state and decreased memory function in some patients, especially the elderly and those with preexisting dementia. Monoamine oxidase inhibition is considered quite benign when used alone, but may potentiate certain side effects when used in combination with other compounds. Ergot alkaloid medication, which is usually combined with levodopa, often induces severe psychiatric complications. Typical findings with levodopa treatment indicate little or no positive impact on cognition, apart from nonspecific arousal and alleviation of concomitant depressive affect. Guidelines for the management of neuropsychological and psychiatric side effects are suggested.