Legalization of “smokable” medical marijuana was associated with significantly increased THC use per certified patient in the Florida medical marijuana program: An interrupted time series analysis

Background/Objective: Tetrahydrocannabinol (THC) is the primary psychoactive cannabinoid in cannabis. THC has potential therapeutic efficacy for some conditions but can lead to adverse drug events when used in higher concentrations. Higher concentrations are typical for smokable medical marijuana (MMJ) products which often contain 20 % THC or more. On March 18, 2019, Florida Senate Bill 182 (SB182) authorized cannabis flower for smoking. The objective of this study was to assess the effect of SB182 on the weekly dispensed amount of THC per certified MMJ patient in Florida. Methods: Data were obtained from the Florida Department of Health Office of Medical Marijuana Use (OMMU) weekly reports, which detailed aggregate MMJ utilization from 04/06/2018 (onset of reporting) until 03/13/2020 (onset of COVID-19 emergency orders). We calculated the weekly amount of dispensed THC per certified patient by summing the total weekly amount of THC in dispensed MMJ across all non-smokable and smokable routes of administration in the pre- and post-periods. These totals were divided by total certified MMJ patients in that week. Given the lack of information of THC content in smokable MMJ products in Florida, we calculated THC amounts using averages of THC concentrations in smokable products (10% and 20%) based on published estimates from other states with MMJ programs. Interrupted time series analysis without control was conducted by fitting a generalized least squares linear model to estimate changes in the overall trend and changes in the level after SB182. We used a phase-in period to allow for time between the first dispensed MMJ products in a form of smoking (3/22/2019), and measurable effects of SB182 (07/19/2019). Autocorrelation and moving averages were ruled out by using autocorrelation and partial autocorrelation plots. Results: In the scenario with 10% average THC in smokable products, SB182 led to a significant level increase of 35.1 mg (95% CI: 4.85-56.34 mg) in the weekly dispensed amount of THC per MMJ patient. This was an increase of roughly 10.7% compared to the estimated amount in the week before the phase-in period (328.20 mg). In the same scenario, a continuously increased trend of 2.23 mg per week (95% CI: 1.16-3.31 mg) was observed in the 35 weeks following SB182. In the second scenario (assumed 20% average THC in smokable products), SB182 was associated with a level increase of 138.4 mg (95% CI: 102.14-174.75 mg) in the weekly dispensed amount of THC per MMJ patient, which corresponds to an increase of 42.2%, compared to 328.20 mg, and a trend increase of 5.62 mg (95% CI: 4.33-5.61 mg) per week in the following 35 weeks from law implementation. Conclusion: The inclusion of smokable MMJ in the Florida MMJ program was associated with a significant increase of the weekly dispensed amount of THC per certified MMJ patient, by increasing the level, as well as the overall trend following law implementation. Further studies should investigate the potential health and safety impacts of increases in dispensed THC in MMJ programs.