People experiencing a first episode of psychosis are three times more likely to smoke tobacco than healthy controls, according to researchers, suggesting that smoking plays a role in the development of psychotic disorders.
Clinicians have generally attributed the link between smoking and psychosis to patients using smoking as a method of self-medication, however a study published in The Lancet Psychiatry suggests smoking could play a bigger role than that.
"While it is always hard to determine the direction of causality," said Dr. James MacCabe, a senior lecturer at King's College London, in a press release, "our findings indicate that smoking should be taken seriously as a possible risk factor for developing psychosis, and not dismissed simply as a consequence of the illness."
Researchers analyzed data on 15,000 smokers and 273,000 non-smokers collected during 61 observational studies, finding that 57 percent of people experiencing their first episode of psychosis were smokers. They also found that people who smoked cigarettes every day developed disorders roughly a year earlier than those who don't smoke.
"Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia," said Sir Robin Murray, a professor of psychiatric research at King's College London. "It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop."
The association is clear, researchers said, however the lack of data regarding consumption of other substances, in addition to the effect of genetics and environment on the development of psychosis, requires further research to establish an explanation.