Few studies let marijuana off the hook, and yet its harms seem unclear or modest compared to tobacco or alcohol — making it hard to stand in the way of the people who want to smoke it, the industry that wants to sell it, and the politicians who want to spend its tax revenues.

Cortical thinning is a form of brain degeneration associated with older age, but Vermont researchers in 2021 found through medical imaging that it accelerated in adolescents who regularly used marijuana.

Substance abuse also rewires the brain's reward system to prefer drugs, including marijuana, over other sources of happiness, said Anna Zilverstand, a U neuroimaging expert.

Reznikoff didn't think Minnesota was ready for medical cannabis in 2014 when the state approved a tightly-regulated program that now provides access to 40,000 people with 19 different qualifying conditions.

Minnesota shouldn't expect legalization to prompt dramatic societal change, other than a windfall of tax revenues, according to a 2021 analysis by the Cato Institute, a libertarian think tank in Washington, D.C.

Dr. Mustafa al'Absi at the U medical school's Duluth campus has been studying how trauma alters brain function and makes people more susceptible to marijuana use and addiction.