Are recreational cannabis laws associated with declining medical cannabis program enrollment in the U.S.? An analysis of cardholder enrollment and demographic characteristics from 2013 to 2020

Background: There is speculation that enrollment in U.S. state medical cannabis programs differs depending on whether adult recreational cannabis use is legal. If true, this could have implications for public health and policy. Methods: Using medical cannabis registry data from U.S. states with a mandatory registry between 2013 and 2020 (N = 23 states), this study examined time-trends in medical cannabis cardholder enrollment and tested whether enrollment trends differed depending on adult recreational cannabis legalization. Results: Multilevel models showed that time-trends for registered active medical cardholders differed during years when adult recreational cannabis use was legal versus not legal (time*recreational cannabis law interaction: b = -0.004, p < 0.01, 95% CI = -0.005, -0.003). The population prevalence of registered active medical cardholders increased over time in years when recreational cannabis was not legal (i.e., medical-only years; b = 0.004, p < 0.001, 95% CI = 0.003, 0.004, corresponding to an increase of 380 cardholders per 100,000 people per year), and decreased in years when recreational cannabis was legal (i.e., recreational years; b = -0.001, p < 0.001, 95% CI = -0.002, -0.001, corresponding to a decrease of 100 cardholders per 100,000 people per year). Time-trends were similar for each sex (male, female) and age group (18–30/35, 30/35+), with each cardholder group showing increases in medical-only years and decreases in recreational years. In medical-only years, there were no differences in enrollment time-trends across sex, but older cardholder (30/35+) enrollment increased at a faster rate than younger cardholder enrollment (18–30/35) (F = 16.199, p < 0.001). In recreational years, male cardholder enrollment decreased at a faster rate than female cardholder enrollment (F = 7.347, p < 0.01), but there was no difference in trends across age. Three states, all with medical-only years, provided data on ethnicity/race. Results showed significant increases from 2016 to 2020 in enrollment of White, African-American, and Hispanic individuals. Conclusions: Findings suggest that recreational cannabis legalization is associated with decreasing enrollment in medical cannabis programs, particularly for males.