Hallucinogen use linked to 2.6-fold increase in risk of death for people needing emergency care

People seeking emergency care for hallucinogen use were at 2.6-fold higher risk of death within 5 years than the general population, according to a new study published in CMAJ (Canadian Medical Association Journal) https://www.cmaj.ca/lookup/doi/10.1503/cmaj.241191.

The use of hallucinogens, such as ketamine, psychedelics, psilocybin, LSD, ayahuasca, and MDMA (Ecstasy), has rapidly increased since the mid-2010s, especially in Canada and the United States. In the US, the percentage of people reporting they used hallucinogens more than doubled from 3.8% in 2016 to 8.9% in 2021. “In Canada, an estimated 5.9% of people used a psychedelic such as LSD or psilocybin in 2023, with use as high as 13.9% in people aged 20–24,” says Dr. Daniel Myran, a family physician and public health and preventive medicine physician researcher with ICES, the Bruyère Health Research Institute, and The Ottawa Hospital.

Increasing use may partially reflect growing medical and societal interest in pairing psychedelics with psychotherapy for mental health and substance use disorders. However, although psychedelic-assisted therapy trials have generally been safe, there are few data about whether hallucinogens might increase the risk of adverse events, such as thoughts of suicide and death, when used outside of carefully controlled clinical trial settings or in populations currently excluded from trials.

“Despite the growing popularity of hallucinogen use, we know surprisingly little about potential adverse effects of hallucinogens, such as mortality risks. Contemporary clinical trials have not observed any short-term increase in risk of severe adverse events, including death, for trial participants. However, these studies involve careful supervision and therapy for trial participants and exclude people at high risk of adverse outcomes,” says Dr. Myran.

To better understand if there is an association between hallucinogen use and increased risk of death, researchers looked at health care data held by ICES on emergency department visits, hospitalizations, and outpatient physician visits for more than 11.4 million people in Ontario aged 15–105 years. Of the total group, 7954 (0.07%) sought acute care for hallucinogen use. The risk of death within 5 years for people who sought acute care for hallucinogen use was almost 10 times that of someone of the same age and sex in the general population. Individuals who received acute care for hallucinogen use had more medical comorbidities.

After accounting for other mental health conditions and substance use along with medical comorbidities (which were generally much more common in those using hallucinogens than the general population) people with acute care visits involving hallucinogens remained at elevated risk of death (2.6-fold higher).

People needing acute care for hallucinogen use were more likely to live in low-income neighbourhoods, to have been homeless at the time of a previous acute care visit, to be long-time residents of Canada, to have chronic health conditions, and/or to have received care for a mental health problem or substance use disorder in the previous 3 years. They were at higher risk of death than people who sought alcohol-related acute care, but at lower risk of death than people needing acute care for opioid or stimulant use.

“The findings highlight the need for ongoing investigation of and communication about both potential benefits and risks from hallucinogen use, particularly use outside clinical trial settings, given rapid increases in general population use,” says Dr. Marco Solmi, a psychiatrist at The Ottawa Hospital and associate professor, University of Ottawa.