Does the legalisation of cannabis for medicinal use impact private health insurer prescription drug expenditures?

We evaluate whether health insurer aggregate prescription drug expenditures change after the legalisation of medicinal cannabis using U.S. health insurer financial filings reported to state insurance regulators and compiled by the National Association of Insurance Commissioners for private health insurers from 2010 to 2018. We analyse this question for health insurers in the individual market, which includes plans sold on the Affordable Care Act exchanges, the small group market, which consists of fully insured plans sold to employers with fewer than 50 employees, and the large group market, which consists of fully insured plans sold to employers with more than 50 employees. For all three markets, the treatment effects are not significant. Thus, we find no impact of medical cannabis legalisation on health insurer prescription drug expenditures, despite the potential disruption to the health insurance market. Had legalisation increased prescription drug expenditures, the increases in cost would have been borne by enrollees, which is troubling since healthcare costs are rising faster than inflation.