Smoking may help trigger serious mental illnesses such as schizophrenia


Everyone already knows smoking is bad for you – but if you needed another reason to quit, a new study suggests it may help trigger serious mental illnesses too.

Scientists found lighting up can triple the chances of developing psychosis.

Before the study, the fact that people with psychotic mental illnesses are more likely to be smokers was put down to other factors, such as self-medication or obtaining relief from distress.

But now researchers believe something in tobacco might actually be responsible – as well as genetic and environmental influences.

Dr James MacCabe, a member of the team from King’s College London, said: “While it is always hard to determine the direction of causality, 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.”

By making 61 observational studies of almost 15,000 people who smoked and 273,000 who didn’t, the team found 57% of people treated for a first episode of psychosis were smokers.

The study also showed that daily smokers became psychotic around a year earlier than non-smokers.

But it also acknowledged the relationship between cause and effect is difficult to prove – with another potential theory being a possible link between smoking and excess dopamine, a brain chemical that plays a role in transmitting nerve signals.

Professor Sir Robin Murray, from the Institute of Psychiatry, Psychology and Neuroscience at King’s College, said: “Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia. It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.”

A proven link has already been found between cannabis use and psychosis in genetically vulnerable people.

So the moral of the scientific study is: don’t smoke.

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