These findings come as psychedelics, a type of hallucinogen, grow in popularity across North America in both recreational and therapeutic contexts. Hallucinogens include drugs such as psilocybin, LSD, DMT (Ayahuasca), and MDMA (Ecstasy).
The study, which followed over 9.2 million individuals in Ontario, Canada, found that those with a hallucinogen-related emergency department (ED) visit had a 21-fold increased risk of developing schizophrenia compared to the general population.
Even after considering an individual's co-occurring substance use and mental health disorders, the study found a 3.5-fold increased risk of schizophrenia.
"Our findings underscore a concerning link between hallucinogen use that requires care in the emergency room and increased risk of schizophrenia," says Dr. Daniel Myran, a Canada Research Chair in Social Accountability at the University of Ottawa, ICES Adjunct Scientist, Investigator at the Bruyère Health Research Institute, and Clinician Investigator at The Ottawa Hospital.
"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," adds Myran.
Published in the journal JAMA Psychiatry, researchers analysed health data for people aged 14 to 65 years old living in Ontario from 2008 to 2021.
The authors looked at changes in the number of ED visits involving hallucinogens over time, along with the risk of being diagnosed with schizophrenia after such visits.
Key findings:
- While annual rates of ED visits involving hallucinogens were stable between 2008 and 2012, they increased by 86% between 2013 and 2021.
- Within three years of an ED visit involving hallucinogens, 4% of individuals were diagnosed with schizophrenia, compared to 0.15% for members of the general population followed for the same period a risk 21 times higher.
- Individuals with ED visits involving hallucinogens were at 4.7 and 1.5 times higher risk of schizophrenia respectively compared to individuals with ED visits involving alcohol and cannabis.
The authors emphasize that their findings do not establish a causal link between hallucinogen use and schizophrenia and that much more information is needed about risks associated with different types and use patterns of hallucinogens. However, the study highlights risks associated with hallucinogen use that requires ED care and potentially in individuals with underlying susceptibility to psychosis or schizophrenia. The authors also emphasize the importance of further studies and public health measures to better understand and mitigate these risks.
"Clinical trials of psychedelic-assisted psychotherapy have safeguards, such as excluding individuals with a personal or family history of schizophrenia and close monitoring while participants use hallucinogens. Our findings provide a timely caution about potential risks of hallucinogen use outside of trial settings," says Myran.
"It is also important that we are able to identify those at risk of developing serious adverse events from psychedelics requiring emergency care, so that future trials can screen for baseline risk of complications of psychedelic use and inform safe recruitment practice," says Dr. Marco Solmi, Director of Research at uOttawa Psychiatry Department and Medical Director of the On Track Early Intervention Service for psychosis in Ottawa.
