Association for Public Policy Analysis & Management

Starting with California in 1996, thirty-three states and the District of Columbia have passed medical marijuana laws (MMLs). Although MMLs are aimed at providing patients with the therapeutic benefits of marijuana, they may also increase access to and use of marijuana for recreational purposes, and this may affect other risky behaviors, such as substance consumption or criminal activity. For example, if marijuana is a gateway drug, MMLs could also increase the use of hard drugs, such as cocaine or heroin. Alternatively, if MMLs increase access to marijuana through friends and family members, marijuana users may be less likely to purchase marijuana from drug dealers providing pathways to hard drugs and the initiation of hard drug use by marijuana users may decrease. We investigate whether MMLs affect legal and illegal substance use and criminal behavior by exploiting the variation among states in the presence, timing of adoption, and characteristics of these laws.

We use data from the National Longitudinal Survey of Youth 1997 Cohort, which is a panel data set that follows the lives of a sample of American youth over time (from 1997 to 2015). This data set allows us to apply difference-in-difference and event study models to identify causal effects on individual-level, self-reported criminal activity and use of marijuana, alcohol, tobacco, and hard drugs. State MMLs have considerable variation in their characteristics, which may have important consequences on substance use and crime. Due to the nature of the data and state laws, we are able to examine the effects of MMLs on illegal behavior that may go undetected by law enforcement and investigate how possession limits, cultivation limits, and the availability of dispensaries affect these risky behaviors.

We differentiate between states with various types of MMLs that may affect access to medical marijuana. These state characteristics take into account differences like the presence of state dispensaries, types of patients who qualify for medical marijuana, and cultivation and possession limits. States that allow for a potentially larger number of patients to access medical marijuana are deemed “high level policy” states. Preliminary results indicate that MMLs may have an overall negative and insignificant effect on marijuana consumption, however, states with “high level policy” MMLs show an increase in any marijuana use compared to states with no such law. Similarly, “high level policy” states drive a positive effect for alcohol consumption, smoking and hard drug use. States that pass MMLs also experience a decrease in how many individuals are ever arrested, although not the number of arrests for an individual.