PsychiatryMatters.MD: "Cigarette smoking reduces schizophrenia risk

Study finding suggest that cigarette smoking may actually protect individuals against developing schizophrenia, although researchers warn that any potential benefits of smoking are still far outweighed by the harmful effects.
Stanley Zammit (University of Wales College of Medicine, Cardiff, UK) and colleagues assessed the effect of cigarette smoking at 18 years of age on the risk of developing schizophrenia in 50,087 Swedish individuals, 98% of whom were aged between 18 and 20 years in 1970. Of these, 362 were diagnosed as having schizophrenia by 1996.
Smoking cigarettes between the ages of 18 and 20 years was found to be associated with a lower rate of schizophrenia development later in life, after taking into account potential confounding factors such as IQ, drug use, poor social integration, disturbed behavior, and family income.
Indeed, analysis showed an inverse linear relationship between the number of cigarettes smoked and the risk of schizophrenia, with a hazard ratio of 0.5 for heavy smokers (>20 cigarettes/day) in comparison with non-smokers.
Interestingly, the researchers report in the American Journal of Psychiatry that smoking did not have the same effect on other psychotic illnesses, such as affective psychoses and substance-induced psychoses. This suggests 'smoking may have a rather specific effect in reducing the development "