Minnesota’s health commissioner has authorized a significant expansion of medical marijuana in the state, approving cannabis use for chronic pain and some eye conditions and announcing more stores and methods to deliver prescriptions.

Intractable pain already is the most common qualifying condition for two-thirds of the state’s 18,000 medical cannabis users, but the addition of chronic pain starting in August should dramatically increase the number of legal users. Cannabis also will be permissible for people with age-related macular degeneration, a retinal condition that degrades vision over time.

“The bottom line is that people suffering from these serious conditions may be helped by participating in the program, and we felt it was important to give them the opportunity to seek that relief,” state health Commissioner Jan Malcolm said in expanding to 16 the number of qualifying conditions in Minnesota.

Malcolm rejected petitions by Minnesotans to add anxiety, insomnia, psoriasis and traumatic brain injury as qualifying conditions, citing a lack of scientific evidence to support them. Chronic pain is a much broader category than intractable pain, which under state law is defined as a form of intolerable pain that cannot be addressed with other remedies or medications.

Malcolm said she was moved by success stories of patients with intractable pain, and wanted to expand access so that pain-sufferers didn’t have to exhaust all other remedies first. Public comments issued this fall illustrated the need, especially as opioid medications are being prescribed less for chronic pain due to the risks of addiction and overdose.

“I am in pain all of the time,” said one person, identified in state documents by the initials K.S. “With the changes in opiate prescribing laws, people like me are fighting a (losing) battle.”

State Sen. Melisa Franzen favored adding chronic pain, stating that people should have more “freedom” in finding treatments that work.

“No two stories of chronic pain are the same,” she wrote.

No written statements were submitted opposing the addition of chronic pain as a qualifying condition.

But some doctors remain concerned about the lack of scientific evidence proving that cannabis works — a standard that is usually required in U.S. medicine. Some also worry about the potential for users to suffer addictions and impaired judgment.

The Minnesota Academy of Ophthalmology opposed adding age-related macular degeneration. While the petition in favor of adding the condition referred to “reports of vision improvements and even reversal of the symptoms” for cannabis users, the academy countered that there is no proof of such an effect.

“This would be yet another false hope that would take desperate elderly people’s money with no benefit to them,” Dr. Mary Lawrence, academy president, said in a letter to the health department. She also worried that patients would bypass proven treatments and visits to ophthalmologists if they viewed cannabis as a quick fix.

Federal restrictions on marijuana as an illicit controlled substance have hampered studies, but Minnesota structured its cannabis program as a research project so that it can track whether cannabis is helping patients or causing any side effects.

Minnesota is one of 33 states that have legalized medical marijuana. The state requires patients to be certified by doctors and to receive cannabis from one of two licensed manufacturers. The Legislature this year voted to double the number of storefronts to 16 — with manufacturer LeafLine Labs planning new shops in Willmar, Mankato, Golden Valley and Rogers, and Minnesota Medical Solutions planning them in Woodbury, Blaine, Duluth and Burnsville.

At least one manufacturer predicted a doubling of medical cannabis patients in Minnesota with the addition of chronic pain as a qualifying condition.

Users tripled from 2,000 to 6,000 in one year after intractable pain was added in summer 2016, said Dr. Kyle Kingsley, founder of Minnesota Medical Solutions. “The inclusion of chronic pain as a qualifying condition will help pave the way for even more patients to replace highly addictive prescription opioid pain medications ... as well as illicit, related street drugs.”

Medical cannabis in Minnesota is permissible in inhaled and pill forms, but as of next summer it will also be available in water-soluble powders and sprinkles, as well as in dissolvable lozenges and mints.

The expansion comes as state health investigators are grappling with the causes of 125 probable or confirmed vaping-associated lung injuries, including three deaths. Most of the injuries involved people vaping illicit forms of THC, the psychoactive component of marijuana, although at least two of the injured Minnesotans were on the state’s medical cannabis registry. State officials said both also were vaping illicit substances.

Malcolm said the addition of new forms of medical cannabis in Minnesota would offer alternatives to people concerned about vaping.