Alzheimer’s disease will become eligible for treatment with medical marijuana in Minnesota next year, making it the 14th health condition approved since the state’s cannabis program began in 2015.

The Minnesota Department of Health announced Monday that it was adding the degenerative neurological disorder to the program, despite limited evidence on the effectiveness of treatment with cannabis. Some studies have found that marijuana inhibits the formation of tau proteins that accelerate dementia and memory loss related to the disease.

“Any policy decisions about cannabis are difficult due to the relative lack of published scientific evidence,” said state Health Commissioner Jan Malcolm. “However, there is some evidence for potential benefits of medical cannabis to improve the mood, sleep and behavior of patients suffering from Alzheimer’s disease.”

Malcolm declined to add six other conditions that had been submitted this summer to a state advisory panel. The others were hepatitis C, juvenile rheumatoid arthritis, opioid use disorders, panic disorder, psoriasis and traumatic brain injury.

Other conditions already approved in Minnesota include cancer pain, epileptic seizures, post-traumatic stress disorder (PTSD) and autism.

Minnesota will join 12 states that permit medical marijuana either for Alzheimer’s or related symptoms.

Dr. William Orr, a Minneapolis-based geriatric psychiatrist, supported the petition and argued that advanced Alzheimer’s can make patients confused, aggressive and combative. Benzodiazepines and narcotics can calm these patients, he wrote, but those drugs aren’t federally approved for the purpose and can cause severe, mood-altering side effects.

“I believe that advanced dementia patients with tremendous anxiety, restlessness, and pain will benefit,” he wrote. “Such patients are episodically distraught and become quickly angered and paranoid of staff trying to help them due to their confusion and inability to understand their circumstances.”

The Minnesota Association of Geriatrics took a neutral position, saying that cannabis to treat Alzheimer’s is not well-studied but that it supported further research.

Malcolm said the limited favorable research combined with other factors convinced her to OK Alzheimer’s, which afflicts an estimated 94,000 people in the state and caused 2,220 deaths in 2016.

The risks of long-term marijuana use are unknown, but Malcolm said they aren’t as much of a concern in an older Alzheimer’s population; the average age of onset is 75.

The absence of treatment options also was compelling. The U.S. Food and Drug Administration hasn’t approved a drug for Alzheimer’s since 2003.

Advocates had mixed reactions Monday to the single addition. Some patients already qualify for cannabis in Minnesota under the catchall category of intractable pain, but some doctors refuse to certify them because their specific diseases aren’t on the state list, said Heather Tidd of the Sensible Minnesota marijuana advocacy group. She also led the state panel that reviewed medical marijuana petitions for the commissioner.

Tidd predicted that cannabis would help families living with elderly parents or other loved ones with Alzheimer’s.

“It will help with anxiety and aggression,” she said.

Whether cannabis will be accessible to Alzheimer’s patients in memory care facilities or nursing homes is another question. Marijuana remains an illicit controlled substance under federal law, which might discourage nursing facilities that depend on state and federal revenue sources.

Malcolm said some nursing homes already support marijuana use for patients with qualifying conditions, but some don’t allow it.

Patients seeking medical marijuana from the state’s two distributors must first obtain certification from one of 1,391 authorized doctors or other practitioners in the state. Cannabis products are then sold to them in liquid or pill forms.

Curing Alzheimer’s — in mice

The state uses data from certified patients to assess whether the potential benefits of medical cannabis outweigh the known disadvantages, including impaired judgment and addiction risks. One study earlier this year found that 60 percent of surveyed patients with intractable pain believed cannabis was helping, and that 43 percent of their doctors agreed.

The state listed 12,207 patients in its cannabis registry this September, up from 7,007 a year earlier. Last year’s additions of autism and sleep apnea as qualifying conditions did not fuel the increase. Only 396 people with either of those conditions were registered this September.

Most people were registered due to intractable pain, a condition added in 2016. The 7,917 people with that condition made up 65 percent of the registry. PTSD and muscle spasms were the next most common conditions.

Dr. Ronald Petersen said he would consider the option if patients or their relatives requested marijuana for Alzheimer’s — with the understanding that it might relieve agitation, but that it hasn’t been proven to treat the disease. A few of his patients are already taking it, but for conditions other than Alzheimer’s, he noted.

Some studies have found that cannabis disrupts the tau proteins that are a hallmark of Alzheimer’s and inhibit brain function. But they were only in animal models, said Petersen, who directs the Mayo Clinic Alzheimer’s Disease Research Center and serves as a science adviser to the Alzheimer’s Association.

“We have cured Alzheimer’s disease time and time again” — in lab and animal models, he said. “But that hasn’t translated to humans yet.”