Marijuana Policy Project

Replicating a prior study, but controlling for state characteristics and measurement error, researchers found that medical marijuana laws have little discernible impact on teen marijuana use or perceptions of the risk of marijuana use in those states. In fact, their research showed that passage of medical marijuana laws actually resulted in a slight decrease in teen marijuana use.

Using data from the national and state Youth Risk Behavior Surveys and other government sponsored data collections, researchers from the Universities of Washington, Oregon, and Colorado at Denver found no association between medical marijuana laws and increased teen marijuana use. They concluded, "[o]ur results are not consistent with the hypothesis that legalization leads to increased use of marijuana by teenagers."

Replicating prior published study results that showed higher marijuana use rates in states with medical marijuana laws, researchers examined the link between those laws and teen marijuana use. Results showed that medical marijuana laws "decreased past-month use among adolescents by 0.53 percentage points and had no discernible effect on the perceived riskiness of monthly use," leading the authors to conclude that evidence linking medical marijuana laws to increased teen marijuana use was "limited."

Comparing 101 youths (ages 12-22) with positive symptoms of psychosis to 59 healthy controls of the same age over a period of three years, this study's authors found that, of those clinically predisposed to psychosis, those who used marijuana tended to demonstrate better social functioning. Results also showed that lifetime marijuana use or abuse did not lead to psychosis, even among those youths clinically predisposed to psychosis.