A cross-national comparison of nonmedical and medical use of psychedelic drugs in the international cannabis policy study

BACKGROUND: We know little about the extent psychedelic substances are consumed therapeutically and/or discussed with medical professionals despite renewed global interest in these substances. METHODS: We examined self-reported responses from the 2023 International Cannabis Policy Study (ICPS) in repeated cross-sectional surveys in Canada, the United States, Australia, and New Zealand. The survey included questions on lifetime, past year, and past month use of psilocybin, LSD, MDMA, and ketamine. It inquired about respondents' discussions with medical professionals, their self-reported medical use, and related adverse events. We estimate the mean proportion rate for each of these using logistic regression methods that adjust for demographics, country, and sampling weights. FINDINGS: Estimated results suggest nineteen per cent of all ICPS respondents reported lifetime use of one of the four substances. Psilocybin was the most commonly estimated to be used in one's lifetime and in the past year, followed by LSD and MDMA. Estimated prevalences of ever using psilocybin were higher among respondents from Canada (16.3%, CI: 15.6-16.9%) than the USA (13.0%, CI: 12.3-13.6%) and New Zealand (12.1%, CI: 10.4-13.8%). Estimated rates of psilocybin ever use in Australia were significantly lower (7.8%, CI: 6.8-8.8%). An estimated 10-20% of respondents who report ever-use of a psychedelic asked their medical provider about medical use, and over a third who had used in the past year reported experiencing an adverse health effect. Estimated rates of past month use were low for all countries. INTERPRETATION: Consumer interest in therapeutic use of psilocybin, MDMA, LSD, and ketamine has surpassed the pace of clinical trials and therapeutic use provisions. These provisions do not necessarily equate to patient access and dual use motivations are not uncommon. Access via nonregulated pathways and self-initiated use in the absence of medical supervision may influence the proportion of individuals who experience adverse events.