Available online 11 November 2022, 102700

Abstract

We exploit shocks to US federal enforcement policy to assess how legal medical marijuana market size affects youth marijuana use and consequences for youth traffic-related fatalities. Using hand-collected data on state medical marijuana patient rates to develop a novel measure of market size, we find that legal market growth increases youth marijuana use. Likely mechanisms are lower prices and easier access. Youth die more frequently from alcohol-involved car accidents, suggesting complementarities for youths. The consequences of marijuana legalization for youth are not immediate, but depend on how supply-side regulations affect production and prices.

Section snippetsYouth use and legal medical marijuana access

Youth marijuana use differs from adult use in several ways that interact with regulatory design. First, in the US, people under the age of 18 have very limited legal access to medical marijuana because all states have imposed legal age-limits of 18 years. While individuals under age 18 can qualify for medical marijuana, they have stricter qualifying standards and require parental consent.4

State markets and federal enforcement over time

As of December 2020, 36 states and Washington D.C. had enacted laws providing protections for the use of medical marijuana. In most states, medical marijuana patients must register in order to access medical marijuana and be protected from state arrest. While states vary slightly in the specific information required of applicants, typically individuals must obtain a physician’s certification that they have a qualifying medical condition, provide verification of residency, and submit an

Data

Our paper offers a novel measure of medical marijuana market size, the number of registered medical marijuana patients per capita. In this section, we discuss this measure in detail and summarize sources for the policy and outcome data.

Empirical framework

We use three main frameworks to assess how use and negative health externalities respond to medical marijuana market size. We first establish that our measure of market size responds to federal enforcement efforts. Next, we exploit this natural experiment to test how changes in market size affect youth use. Finally, we assess changes in fatal car accidents in response to changes in market size.

Results

We begin by presenting results from the first stage, where we relate changes in federal enforcement to medical marijuana patient registration rates. Next, we present results for marijuana consumption outcomes, as well as exploration of potential mechanisms that may drive these results. After exploring potential mechanisms, we assess mortality from motor vehicle accidents.

Conclusion

Using newly collected data and a novel identification strategy, we study how adolescent marijuana use and associated public health externalities change in response to medical marijuana market size. Contrary to prior research that focused on passage of MMLs and found no effect, we find youth marijuana use responds to medical marijuana market size. Our estimates suggest that if a state where marijuana is illegal were to reach the median per capita medical marijuana registration rate, past-month

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