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Study: Smokers more likely to develop psychosis

Friday, 10 July 2015 10:57 AM [ Last Update: Friday, 10 July 2015 10:57 AM ]

Researchers say smokers are more likely to develop the disorder and at a younger age.

Cigarette smokers are at risk of psychosis, according to researchers who believe tobacco and cannabis could cause schizophrenia.

The author of the study, Dr James MacCabe from Institute of Psychiatry, Psychology and Neuroscience said: “Having psychosis is a very distressing thing – hearing voices, having delusions”.

“The argument goes, why wouldn’t people smoke to alleviate the distress? They might hope it would help with the symptoms and their impaired thinking processes and possibly counter the side-effects of antipsychotic drugs," he said.

Data collected from different studies and published in the Lancet Psychiatry Journal shows those who smoke on a daily basis are at an increased risk of developing psychosis, with 57% of those seeking mental health services being regular smokers. It also identifies non-smokers do not develop the condition as fast as those who do smoke.

However, Robin Murray, professor of psychiatric research at King's Institute of Psychiatry, Psychology & Neuroscience said there is no concrete proof that smoking causes schizophrenia.

“We can’t say that we have proof that cigarette smoking causes schizophrenia,” he said.

He added: “Indeed it is very difficult to point to any particular factor and say it causes schizophrenia. It is a bit like heart disease – there are a number of risk factors. You inherit some vulnerability and … are exposed to various things which increase the risk to your life.”

While most experts believe cannabis causes psychosis and schizophrenia, the authors of the study say the data they collected may not have included cannabis use. However, they are adamant on the connection between tobacco and psychosis.

“Excess dopamine is the best biological explanation we have for psychotic illnesses such as schizophrenia,” said Murray. “It is possible that nicotine exposure, by increasing the release of dopamine, causes psychosis to develop.”

Prof Michael Owen, director of the Institute of Psychological Medicine and Clinical Neurosciences at Cardiff University, supported the study, saying it makes “a pretty strong case that smoking is of causal relevance to schizophrenia”.

“The fact is that it is very hard to prove causation without a randomised trial, but there are plenty of good reasons already for targeting public health measures very energetically at the mentally ill,” he said.

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