Three well-controlled, large studies in New Zealand and Australia of those who used marijuana before age 17 reveal adverse changes to developing brains and significant negative impacts on motivation, drive, and cognition. Subjects were followed for up to 30 years. A dose-response relationship was observed between frequency of use and dropout rates, suicide attempts, failure to get a college degree, and use of illicit drugs.
PositiveTip: Parents must warn teens and young adults about the major adverse effects of marijuana use.