State Variation in U.S. Medical Cannabis Limits, Restrictions, and Therapeutic Cannabis Dosing

Wide variation exists in the possession limits of cannabis products sold for medical use in the U.S. as well as the tetrahydrocannabinol (THC) content of cannabis products. Prior work has found that legal limits on recreational cannabis sold per transaction may promote moderate use and diversion. This paper finds similar results for monthly medical cannabis limits. In the present analyses, state limits on medical cannabis were aggregated and converted into 30-day limits and 5 milligram (mg) THC doses. Grams of pure THC were calculated using plant weight limits and medical cannabis median THC potency aggregated from Colorado and Washington state medical cannabis retail sales data. Weight in pure THC was then broken down into 5 mg doses. Weight-based possession limits of cannabis for medical use varied widely across states (range: 1.5-762.05 grams pure THC per 30 days), with three states lacking a quantifiable weight limit (in which limits are not by weight but by physician's recommendation). States generally do not impose limits on the potency of cannabis products, therefore small differences in weight limits can result in large differences in the amount of total THC allowed to be sold. Assuming a typical medical dose of 5 mg and the median THC potency of 21%, current laws allow for sales of 300 (Iowa) to 152,410 (Maine) doses per month. Current state statutes and methods of cannabis recommendation allow patients to increase therapeutic THC doses independently, and perhaps unknowingly. High THC content products combined with the higher purchase or possession limits allowed by medical cannabis laws may lead to an increased potential for overconsumption or diversion.