Does Smoking Increase Schizophrenia Risk?

Quitting smoking is just about one of the hardest things you can do, but new research suggests there may be yet another serious reason to consider it. The new study in The Lancet Psychiatry finds a link between smoking and the development of schizophrenia. Whether the link is causal or not remains to be seen, but the authors suggest that it may well be, given how nicotine is known to affect the brain. More studies may be necessary to understand the link fully, but in the meantime, smoking has enough marks against that it probably doesn’t even need another as evidence that it’s bad.

The link between smoking and schizophrenia isn’t exactly news: Researches have known about it for a long time, but mostly chalked it up to self-medication – that is, people with schizophrenia are simply self-medicating their symptoms, which may be stressful and disturbing to experience. It certainly makes sense. But the authors of the new study, from Kings College London, carried out a meta-analysis to see whether there might be more going on – like a link in which smoking may actually increase the odds that schizophrenia will develop in the future.

The team looked at 61 past studies of almost 290,000 participants, and ran statistical analyses to determine any connections between smoking and the likelihood of having or developing schizophrenia. They found that daily smokers were at least two times more likely to develop schizophrenia than non-smokers.  The team also found that daily smokers tended to develop psychosis about a year earlier than non-smokers.

Though causation certainly wasn’t illustrated, it is possible, given how nicotine affects the brain’s dopamine system, which is affected in schizophrenia. “Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia,” said study author Sir Robin Murray. “It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.” On the flipside, researchers know that smoking is linked to reduced risk of Parkinson’s disease, which caused by too little dopamine in certain areas of the brain.

Nevertheless, more studies will be needed before we really understand how nicotine affects the risk of brain diseases of various types. In the meantime, it’s always a smart idea to stop smoking, given the laundry list of ailments it causes, and the evidence that the body and brain can rebound considerably after people stop.

In any case, there seems to be more going on than simple self-medication – the connection may work both ways, at least in some people. Perhaps for those who are genetically predisposed to schizophrenia, smoking, in addition to other lifestyle factors, may act as a catalyst. “While it is always hard to determine the direction of causality,” said study author James MacCabe, “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.”

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Source: Forbes