New research suggests that smoking can triple the chances of developing psychosis.

Previously the fact that people with psychotic mental illnesses are more likely to smoke has been put down to non-causal factors, such as obtaining relief from distress or self-medication. But scientists now believe something in tobacco might be responsible, alongside genetic and environmental influences.

Researchers from King’s College London analysed data from 61 observational studies involving almost 15,000 tobacco users and 273,000 non-users. They found that 57% of people treated for a first episode of psychosis were smokers......