Abstract Body (Do not enter title and authors here):

Background: Legal recreational cannabis sales (“legalization”) began earlier in the Western U.S. (January 2014) versus non-Western states (November 2018), providing a natural experiment to study its impact.

Aim: To test the association between legalization and cardiovascular hospitalizations.

Methods: Using the National Inpatient Sample (NIS), we performed a difference-in-differences analysis of the association between legalization and hospitalization rates for 6 cardiovascular diagnoses, a positive control (cannabis-related diagnoses), and 2 negative control diagnoses (opioid-related and urinary stones). We used survey-weighted Poisson regression modeling adjusted for age, sex, income, and race/ethnicity to estimate the relative change in hospitalization rates associated with each year of legalization.

Results: Each year of legalization was associated with the following relative change in the hospitalization incidence rate ratio (cIRR) compared with regions that did not legalize: cannabis-related diagnoses [cIRR 1.138, 95% CI 1.066-1.214, p < 0.001], atrial fibrillation/flutter (AF) [cIRR 1.023, 95% CI 1.010-1.035, p<0.001], heart failure (HF) [cIRR 1.037, 95% CI 1.029-1.046, p < 0.001], myocardial infarction (MI) [cIRR 1.031, 95% CI 1.014-1.048, p < 0.001], ischemic stroke [cIRR 1.011, 95% CI 0.999-1.024, p=0.078], venous thromboembolism (VTE) [cIRR 1.009, 95% CI 0.999-1.020, p =0.066], and ventricular tachycardia (VT) [cIRR 1.019, 95% CI 0.993-1.046, p=0.161]. For falsification testing, there was no change in hospitalizations for urinary stones [cIRR 1.006, 95% CI 0.986-1.027, p = 0.535] or opioid-related diagnoses [cIRR 0.966, 95% CI 0.927-1.006, p = 0.091].

Conclusions: Recreational cannabis legalization was associated with increased hospitalizations for AF, HF, and MI. Further work is needed to replicate these findings in state-level analyses, ideally accounting for different cannabis formulations.