Changes over time in hallucinogen-related emergency department visits in Ontario, Canada.

Recent increasing interest in hallucinogens has underscored the critical gaps in our understanding of their adverse health effects and healthcare usage over time. The current study aimed to examine changes in emergency department (ED) visit rates involving hallucinogens, clinical outcomes of visits and the characteristics of individuals with ED visits involving hallucinogens. Repeated cross-sectional study using health administrative data. Ontario, Canada. All individuals aged 10 years and older living in Ontario, Canada, from 2008 to 2023 (population of 13 492 974 in 2023). Annual rates of ED visits involving hallucinogens overall and by demographic and clinical subgroups. Linear regression was used to calculate the average annual percent change (AAPC) in rates of visits. We identified 7735 individuals with an ED visit involving hallucinogens [median (interquartile range) age at the time of visit, 24 (19-33) years; 71.5% male] who incurred 8274 visits. Visits displayed high acuity, with 54% arriving by ambulance and 13.2% requiring hospitalization. In 42% of visits another substance or co-morbid mental health diagnosis was noted as contributing to the visit. Annual rates of ED visits involving hallucinogens increased by 97.9% between 2008 and 2023 (3.3 to 6.5 visits per 100 000 individuals) with visits increasing on average by 5.6% per year [AAPC = 5.6%; 95% confidence interval (CI) = 3.9%, 7.3%]. Relative increases between 2008 and 2023 were higher in those aged 25-44 (relative change (RC) 192.5%: AAPC = 8.5%; 95% CI = 6.0, 11.0] compared with other ages (age 45 + RC 125%: AAPC = 5.5%; 95% CI = 3.6, 7.3; age 19-24 RC 75.0%: AAPC = 5.3%; 95% CI = 3.4, 7.3). Visits increased more in individuals with anxiety disorders (RC 247%: AAPC = 7.5%; 95% CI = 5.2%, 9.9%) or prior diagnosis of schizophrenia (RC 401%: AAPC = 12.2; 95% CI = 8.2%, 16.4%) than those without any mental health disorder (RC 85.5%: AAPC = 4.9%; 95% CI = 3.1, 6.7). Comparable changes over time were observed in males (RC 101.1%: AAPC = 4.7; 95% CI = 2.9, 6.5) and females (RC 85.9%: AAPC = 6.0%; 95% CI = 4.2, 7.8) and for those in the richest (RC 124.0%: AAPC = 5.7%; 95% CI = 4.6%, 6.9%) or poorest neighbourhoods (RC 70.2%: AAPC = 5.2%; 95% CI = 3.7%, 6.7%). The 97.9% increase in emergency department visits involving hallucinogens in Ontario, Canada, from 2008 to 2023 may reflect rising hallucinogen use and the need for ongoing monitoring, particularly in adults aged 25-44 years and those with co-morbid mental health diagnoses.