Cannabis legalization and increasing cannabis use in the United States: Data from urine toxicology testing in emergency room patients.

Objective: Rates of cannabis use disorder (CUD) appear to be increasing nationally, with increases greater in states that legalized cannabis use. However, as legalization has progressed and stigma declined, some of these apparent increases could be due to greater willingness of survey respondents and patients to acknowledge cannabis involvement. Biological indicators of cannabis use overcome some concerns about trends denoted by self-report data whose validity is potentially changing over time. Our objective was to investigate the relationship between medical cannabis laws (MCL) and recreational cannabis laws (RCL) and the prevalence of cannabis-positive urine drug screens (UDS) in a large patient sample.

Methods: Veterans Health Administration (VHA) emergency department (ED) patients aged 18-75 years with ≥1 ED visit for any reason in a given year from 2008 to 2019 were included. Staggered-adoption difference-in-difference analysis was used to estimate the association between MCL and RCL enactment on cannabis-positive UDS, fitting adjusted linear binomial regression models.

Results: Adjusted cannabis-positive UDS prevalences increased from 16.4 % to 25.6 % in states with no cannabis law, 16.6 % to 27.6 % in MCL-only-enacting states, and 18.2 % to 33.8 % in RCL-enacting states. MCL-only and RCL enactment was associated with a 0.8 % (95 % CI, 0.4-1.0) and 2.9 % (95 % CI, 2.5-3.3) increase in prevalence of cannabis-positive UDS, respectively.

Conclusions: MCL and RCL enactment played a significant role in the overall increases in cannabis-positive UDS among ED patients. The increase in a biological measure of cannabis use helps reduce concerns about reporting bias as cannabis becomes increasingly legalized.