Patients who present to ED after hallucinogen use are 21 times more likely to develop schizophrenia spectrum disorder within three years compared with the general population, a retrospective study suggests.

Even after adjusting for other mental health disorders and substance use, people with a hallucinogen-related ED visit had a 3.5-fold increased risk of schizophrenia, the Canadian researchers found.

“While there is enormous enthusiasm for psychedelic-assisted therapy as a new mental health treatment, we need to remember how early and limited the data remains for both the benefits and the risks,” said lead author Dr Daniel Myran, from the University of Ottawa.

The team tracked insurance data for 9.2 million Canadians (mean age 40) who had no history of psychosis and at least one ED visit over a median timeframe of five years.