Medical marijuana laws have been suggested as a possible cause of increases in marijuana use among adolescents in the United States. This study evaluated the effects of medical marijuana laws on adolescent marijuana use from 2003 through 2011.
The authors used data from the Youth Risk Behavior Survey and a difference-in-differences design to evaluate the effects of passage of state medical marijuana laws on adolescent marijuana use. The states examined (Montana, Rhode Island, Michigan, and Delaware) had passed medical marijuana laws at different times over a period of 8 years, ensuring that contemporaneous history was not a design confound.
Among the states examined, medical marijuana laws have not measurably affected adolescent marijuana use in the first few years after their enactment. Longer-term results, after medical marijuana laws are more fully implemented, might be different.