Smoking could play a direct role in the development of schizophrenia, UK-based researchers said.
The team at King’s College London say smokers are more likely to develop the mental disorder symbolised by a withdrawal from reality and a sense of mental fragmentation.
Published in the ‘Lancet Psychiatry’, the new analysis of 61 separate studies suggests nicotine in cigarette smoke may be altering the brain.
“It’s very difficult to establish causation (with this style of study), what we’re hoping that this does is really open our eyes to the possibility that tobacco could be a causative agent in psychosis, and we hope this will then lead to other research and clinical trials that would help to provide firmer evidence,” said James MacCabe, from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London.
Smoking has long been associated with psychosis, but it has often been believed that schizophrenia patients are more likely to smoke because they use cigarettes as a form of self-medication to ease the distress of hearing voices or having hallucinations.
The team at King’s looked at data involving 14,555 smokers and 273,162 non-smokers.
It indicated that 57 per cent of people with psychosis were already smokers when they had their first psychotic episode, daily smokers were twice as likely to develop schizophrenia as non-smokers, and smokers developed it a year earlier on average.
The argument is that if there is a higher rate of smoking before schizophrenia is diagnosed, then smoking is not simply a case of self-medication.
The overall incidence of the condition is one in every 100 people normally, which may be increased to two per 100 by smoking.
The researchers said nicotine altered levels of the brain chemical dopamine, which has already been implicated in the psychosis.
