Smoking may cause mental illness, new study suggests

SMOKING tobacco may increase the risk of developing schizophrenia and other serious mental illnesses, scientists have suggested.

In a landmark study published today, researchers highlight statistical trends which suggest cigarettes can increase the chance of someone being diagnosed with psychosis. They think nicotine interferes with the way the brain responds to pleasure and reward, which may trigger mental disorders.

Doctors have highlighted in the past the fact that people with psychotic mental illnesses are more likely to be smokers. But until now experts have assumed this is because sufferers are smoking to deal with their distress.

The study suggests for the first time the link may actually be causal. The authors used data from almost 290,000 people to conclude that those with psychosis are more likely to smoke because their habit – alongside genetic and environmental influences – caused their problem.

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 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 found 57 per cent of people treated for a first episode of psychosis were smokers. Psychotic patients were three times more likely to smoke than people without mental illness. The study also showed, on average, smokers became psychotic about a year earlier than non-smokers.