As public attitudes about marijuana shift and some U.S. states legalize it for medicinal or recreational use, the impact of these changes on public safety and health are an active area of research and debate. The public, including youth, increasingly regard marijuana as a safe drug; however, while many uncertainties remain about its overall health effects and its long-term impact on memory and mood, current evidence suggests that marijuana has a significant impact on brain development and various associated behavioral outcomes when it is used heavily during adolescence.