Cigarette smoking: effects on cognitive functions and drug-induced parkinsonism in chronic schizophrenia.

Epidemiological studies suggest an apparent protective effect of cigarette smoking on the risk of Parkinson's disease. There is also a report suggesting that patients with Parkinson's disease who smoke are less likely to develop dementia. I investigated the relationship of smoking to the severity of cognitive functions and presence of drug-induced parkinsonism in a group of 111 neuroleptic-treated chronic institutionalized schizophrenic patients. Patients who smoked had significantly less cognitive impairment (p < .02) and a lower prevalence of drug-induced Parkinsonism (p < .02) compared to nonsmokers. These findings suggest that cigarette smoking may protect against the development of dementia and drug-induced Parkinsonism in schizophrenia.