Many studies have shown that marijuana can negatively affect the cognitive development of adolescents. For some individuals, marijuana use may also initiate opioid use, dose escalation, and opioid use disorder. States that legalize marijuana should help adolescents through regulation of advertising and availability of marijuana-infused edibles. Such policies may assist in protecting neurodevelopment of the adolescent and young adult brain. The federal government should also remove its prohibition of marijuana sales and use, leaving their regulation to state law-makers.