Smoking is linked to psychotic disorders
Chemicals in tobacco may trigger serious mental illnesses such as schizophrenia, a new study suggests.
Research shows that smoking can triple the chances of developing psychosis.
Previously, the fact that people with psychotic mental illnesses are more likely to smoke had been put down to non-causal factors, such as obtaining relief from self-medication.
Now, however, scientists believe something in tobacco might actually be responsible, alongside genetic and environmental influences.
Dr James MacCabe, a member of the research team from King's College London, said: "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."
The researchers analysed data from 61 studies involving almost 15,000 tobacco users and 273,000 non-users.
They found that 57pc of people treated for a first episode of psychosis were smokers. Psychotic patients were three times more likely to smoke.
One theory is a link between smoking and excess dopamine, a chemical that plays a role in transmitting nerve signals.
Professor Robin Murray, from 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."