[Smoking and schizophrenia: epidemiological and clinical features].

FREQUENCY: The prevalence of cigarette smoking is significantly higher among patients with schizophrenia (60-90%) than in the general population (23-30%). While tobacco smoking decreases in the general population (from 45% in the 1960's to 23-30% in the 2000's), smoking in patients with schizophrenia remains high. Patients with schizophrenia smoke more cigarettes than control subjects. Patients smoke more deeply, thereby increasing their exposure to the harmful elements in tobacco smoke. IMPACT OF SMOKING IN SCHIZOPHRENIC PATIENTS: As in the general population, smoking contributes to the reduced life expectancy in patients with schizophrenia. Patients with schizophrenia are at increased risk for cardiovascular disease due to high rates of cigarette smoking. In the Department of Mental Health of the commonwealth of Massachusetts, cardiovascular disease was the factor the most strongly associated with excess mortality. Cardiac deaths were elevated more than six-fold. Weight gain, insulin resistance, metabolic syndrome and diabetes mellitus are frequent in patients with schizophrenia, and may worsen the risk of cardiovascular diseases. It has been reported that the risk for lung cancer in patients with schizophrenia is lower than that of the general population, despite increased smoking. However, in a study conducted in Finland, a slightly increased cancer risk was found in patients with schizophrenia. Half of the excess cases were attributable to lung cancer. IMPROVEMENT OF COGNITIVE DEFICITS: Patients with schizophrenia may use nicotine to reduce cognitive deficits and negative symptoms or neuroleptic side effects. Smoking may transiently alleviate negative symptoms in schizophrenic patients by increasing dopaminergic and glutamatergic neurotransmission in the prefrontal cortex. In patients with schizophrenia, nicotine improves some cognitive deficits: (1) sensory gating deficits and abnormalities in smooth pursuit eye movements associated with schizophrenia are transiently normalized with the administration of nicotine ; (2) high-dose nicotine transiently normalizes the abnormality in P50 inhibition in patients with schizophrenia and in their relatives; (3) in tasks that tax working memory and selective attention, nicotine may improve performance in schizophrenia patients by enhancing activation of and functional connectivity between brain regions that mediate task performance (Jacobsen et al. 2004; Paktar et al.2002); (4) cigarette smoking may selectively enhance visuospatial working memory and attentional deficits in smokers with schizophrenia. However, Harris et al., found that nicotine affects only the attention without effects of nicotine on learning, memory or visuospatial/constructional abilities. In addition, smoking could facilitate disinhibition in schizophrenic patients.