DFL legislators Rep. Zack Stephenson, at podium, and Senator Lindsey Port, left, introduce a bill proposing legalizing the adult use of marijuana with other legislators on Jan. 5 at the Minnesota State Capitol. (David Joles, Star Tribune/The Minnesota Star Tribune)

Opinion editor's note: Editorials represent the opinions of the Star Tribune Editorial Board, which operates independently from the newsroom.

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Ask Minnesota's medical community what the minimum legal age for recreational marijuana use should be — if state lawmakers approve it — and the response is generally some version of this:

"Ideally it would be 25, but that's not happening."

Their resignation reflects reality on several fronts. There is serious momentum at the Legislature to allow adults age 21 and up to use cannabis for nonmedical reasons. If passed, the measure would expand action taken last year at the Capitol to legalize adult use of edibles containing a low dose of THC, the cannabis compound responsible for its high.

Marijuana momentum is also happening, or has happened, elsewhere. Twenty-one states already have enacted measures to regulate cannabis for adult nonmedical use, according to the National Conference of State Legislatures. These states, with no apparent exceptions, have set the age at 21, creating a policy consensus that this is the appropriate age.

Twenty-one is also the minimum age to smoke cigarettes or drink alcohol in Minnesota and most other locations. While there are advantages to setting the same threshold for cannabis, it's important as the debate continues at the Capitol to understand why many in health care would prefer 25 as a minimum age. This knowledge should spur legislators to add or strengthen safeguards in the bill to protect young users.

Medical concerns generally involve research suggesting that brains aren't fully mature until someone reaches their mid-20s. There are significant questions about the impact of cannabis or other substances on still-developing gray matter.

What is known, however, is sobering. A 2019 research review published in the Journal of the American Medical Association network concluded: "Although individual-level risk remains moderate to low ... the high prevalence of adolescents consuming cannabis generates a large number of young people who could develop depression and suicidality attributable to cannabis."

A report from the National Institute on Drug Abuse (NIDA) also notes the link to psychiatric disorders such as schizophrenia, particularly among those with genetic vulnerabilities. "Recent research suggests that smoking high-potency marijuana every day could increase the chances of developing psychosis by nearly five times compared to people who have never used marijuana."

The growing body of research about potentially harmful impacts is a key reason why the Minnesota Medical Association said in a statement that the minimum age should be 25.

While the organization — which represents more than 10,000 physicians, residents and students — is officially neutral on cannabis legalization, it is calling for limits on where these products can be sold, as well as strong packaging and marketing requirements to protect children. It also supports increased funding for addiction treatment through taxes raised on marijuana sales.

The state's Mental Health Legislative Network, which includes the National Alliance on Mental Illness's state chapter (NAMI), as well as the Allina and Children's Minnesota health systems, also sent legislators a letter this month stating that the minimum age should be 25.

Its reasoning: "It is well established now that the adolescent brain continues to develop well into the early 20s and to the age of 25. Research has shown that cannabis use in young people can cause disproportionately adverse effects compared to a fully formed brain."

The network is pushing hard for stronger labeling requirements to warn users under 25 of the risks. It also has called for clear warnings for pregnant women about the potential impact on neonatal development. Another sensible measure it's seeking: more robust funding for the state's First Episode Psychosis program, which provides essential support and early intervention for those encountering this illness for the first time.

The Star Tribune Editorial Board agrees that raising the age to 25 would be ideal but also acknowledges the benefits of setting the age at 21. The same age requirement for tobacco, alcohol and marijuana would provide clarity for consumers and retailers. Raising the age to 25 also could create an illicit market for young users, increasing the risk of products that are adulterated or contain doses higher than indicated.

The adult-use marijuana bill's lead author in the House is Rep. Zack Stephenson, DFL-Coon Rapids. Stephenson has gracefully accepted a number of suggested improvements. This week, he told an editorial writer that he acknowledges the research about young users' risks, but also said that "society has decided in matters big and small that 21 is the age of majority." He also questioned how "tenable" it would be to have different standards for alcohol, tobacco and marijuana.

Stephenson, however, emphasized his respect for organizations such as NAMI and said considering suggestions from health care organizations is "a priority."

That's the right attitude. Medical advocates' concerns should be taken seriously. There are risks inherent in legalizing this drug, and the goal should be to minimize harm.