The impact of recreational cannabis laws on cannabis use disorder during “treat and release” visits to hospital emergency departments in four U.S. states, 2017–2020

States’ legalization of cannabis influences cannabis use and may increase cannabis use disorder (CUD)—a problematic pattern of use leading to significant impairment. Few studies have examined the influence of recreational cannabis legalization on CUD in the emergency department (ED). We used four years of data from the State Emergency Department Databases (SEDD) (2017–2020) from three states (CO, MD, OR) and three years of SEDD from Rhode Island (2017–2019) to examine the relationship between the recreational legalization of cannabis and CUD among “treat and release” ED visits. During the study period, CO and OR were legal for recreational cannabis while it was illegal in MD and RI. We examined the proportion of ED visits for CUD and used multivariate logistic regression to examine the association between recreational legalization and CUD diagnosis. The sample had 17,434,655 ED visits (56.2 % female). The proportion of ED visits for CUD was 0.63 %. Annual rates ranged from 0.67 % (2017) to 0.59 % (2019) and state-level rates were 0.39 % (CO), 0.35 % (OR), 1.03 % (MD), and 0.79 % (RI). Compared to ED visits in legal states, a higher proportion of ED visits in non-legal states were from women (56.8 % versus 55.7 %) and Blacks (40.9 % versus 5.9 %). Compared to states where recreational cannabis was illegal, legalizing cannabis for recreational use was associated with nearly a 50 % decrease in the adjusted odds of CUD (AOR = 0.49, 95 % CI 0.47, 0.52). In summary, CUD rates among “treat and release” ED visits were significantly lower in legalized states than in non-legal states.