Smokers you may need to kick that smoking habit, smoking
tobacco already known to cause cancer and stroke, may be also be a contributor
to mental illness, a new study suggests.
Researchers at King's College London have found that people
who suffer from psychosis are about three times more likely to be smokers.
Although the association between smoking cigarettes and
psychosis - particularly schizophrenia - has been acknowledged before, little
attention has been directed towards the possibility that cigarettes themselves
may increase the risk of psychosis.
The researchers analysed data from 61 observational studies
involving almost 15,000 tobacco users and 273,000 non-users.
The study also showed that daily smokers became psychotic
around a year earlier than non-smokers.
It has long been hypothesized that higher smoking rates
among psychosis sufferers could be explained by people seeking relief from
boredom or distress, or self-medicating against the symptoms or side-effects of
anti-psychotic medication.
But if this were so, researchers would expect smoking rates
to increase only after people had developed psychosis.
The King's College London team said in a statement:
"These findings call into question the self-medication hypothesis by
suggesting that smoking may have a causal role in psychosis."
They stressed they had not conclusively proven that smoking
causes psychosis, saying further research must be done.
But the results did suggest that smoking "should be
taken seriously as a possible risk factor for developing psychosis and not
dismissed simply as a consequence of the illness," they wrote.
The researchers theorised that changes in the brain's
dopamine system may explain the association.
Dopamine is a chemical messenger that helps control the
brain's reward and pleasure centres.
"It is possible that nicotine exposure, by increasing
the release of dopamine, causes psychosis to develop." said King's College
London psychiatric professor Robin Murray
Dr Michael Bloomfield, clinical lecturer in psychiatry at
University College London, said: "Much more research is needed before
scientists can say for certain that smoking definitely increases the risk of
schizophrenia since it remains possible that people who would go on to develop
schizophrenia are more likely to start smoking.
"Regardless of these findings, there is overwhelming
evidence that nicotine use through tobacco smoking is one of the most dangerous
drug problems in the world. Anyone who needs help in stopping smoking should
speak with their doctor."
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