Researchers have found that cannabinoid hyperemesis syndrome, a vomiting condition tied to chronic cannabis use, rose sharply in US emergency departments between 2016 and 2022 and has stayed elevated. As of June 2025, nearly half of US residents live in states with legalized recreational cannabis, and policy shifts have expanded adult-use access through legalization, medical programs, and decriminalization. Among cannabis-related harms, cannabinoid hyperemesis syndrome (CHS) has been described as a growing concern in clinical and public health settings. CHS was first identified in 2004 in Australia and remains a syndrome with uncertain etiology. Proposed neurophysiological mechanisms include downregulation of cannabinoid...