Cannabis Use in United States Has Mirrored Policy Changes Image Cannabis News June 6, 2024 Long-term Trends in Cannabis Use Reflect Legalization Policies, Study Finds. Long-term trends in cannabis use have mirrored policy, with state-level legalization resulting in an increase in use, according to research published online May 22 in Addiction. Jonathan P. Caulkins, Ph.D. from Carnegie Medical Cannabis News Recreational Marijuana News Physician's Weekly