Trends in Hallucinogen-associated Emergency Department Visits and Hospitalizations in California from 2016–2021

Objectives Hallucinogens encompass a diverse range of compounds with increasing scientific and public interest. Risks associated with hallucinogen use are poorly understood. This study aims to evaluate the trends in hallucinogen-related emergency department visits and hospitalizations in California from 2016 to 2021, as compared to alcohol and cannabis visits and hospitalizations Methods We conducted a descriptive study on publicly available data on diagnosis codes associated with emergency department (ED) visits and hospitalizations from the California Department of Healthcare Access and Information (HCAI) to describe hallucinogen, alcohol, and cannabis associated encounters. Results Rates of hallucinogen associated ED visits increased by 69% between 2016 and 2021 compared to a 24% decrease and 1.9% decrease in rates of alcohol associated and cannabis associated ED visits respectively. Rates of hallucinogen associated hospitalizations increased by 74% compared to a 11% increase in alcohol associated hospitalizations and a 19% increase in cannabis associated hospitalizations. Conclusions The large relative, but small absolute, increase in hallucinogen associated ED visits and hospitalizations is concerning given changing public perception and increasing use of these substances. The categorization of a large number of compounds as hallucinogens limits our ability to understand trends in harms with ICD-10 codes. Improved systems for surveillance of potential harms of hallucinogen use are needed.