A large share of Minnesotans using medical marijuana for chronic pain say they're experiencing less discomfort and have reduced their reliance on potentially addictive opioid drugs.

In the state's first report card on cannabis and chronic pain, more than 60 percent of patients responding to a state survey said they benefited greatly from using pot in inhaled or pill forms, and 43 percent of their doctors concurred.

State health officials said patients achieved the gains in the first five months after Minnesota approved cannabis to treat pain, and that many patients reported dramatic turnarounds.

"A lot of these people have really tough lives," said Tom Arneson, research director of the state's medical marijuana program, which started in 2015 for the treatment of nine qualifying conditions, then added intractable pain a year later. "They're really suffering and they are finding out that their lives can be changed" by cannabis use.

Minnesota was the 22nd state to approve marijuana for medicinal use, but state leaders took a unique approach by setting up their program as a grand research project — hoping to address the paucity of U.S. data on whether marijuana offers therapeutic benefits that outweigh any harms.

Patients and doctors receive surveys in the mail twice each year and patients complete health assessments for research purposes each time they pick up new cannabis supplies from one of Minnesota's two approved distributors.

The assessments produce scores that reflect the intensity of patients' pain, and how much it interferes with their lives. Scores improved by at least 30 percent, which is considered clinically significant, for 42 percent of patients who received cannabis for intractable pain, the state reported.

The state had no reports of reactions that were life-threatening or required hospitalization.

Fewer opioid users

Medical records showed that at least 353 patients were taking opioid painkillers when they were certified by doctors to receive medical marijuana. Six months later, nearly 63 percent had reduced or eliminated opioid dosages.

The report also included anonymous comments from pain patients, many of them glowing.

"This program has opened up a world for me I thought I had lost," said one.

The report was based on results for 2,245 patients who took cannabis for the first time in the second half of 2016 for chronic pain.

Not all feedback was glowing. Roughly 10 percent of patients reported no benefit, and as many as four in 10 reported a mild side effect such as fogginess or fatigue. One patient found the effect temporary.

"I definitely noticed a drastic relief in my pain levels. That was so wonderful. I was so hopeful. Then, unfortunately, after a week of using the cannabis regularly, the efficacy ... began to steadily wane."

Placebo effect?

Studies have shown that people can build up tolerance to the mood-altering effects of cannabis, Arneson said, but not to any pain relief it provides. Follow-up studies will be critical to addressing such questions and proving whether cannabis effectively treats pain and other conditions, he added.

Surveys and self reports by patients and doctors don't prove cause and effect; it's possible that Minnesota patients experienced a placebo effect in which they psychologically convinced themselves that cannabis relieved their pain. Arneson also called this an "expectation effect."

Large comparative clinical trials could address these questions, but the cost and federal restrictions on cannabis as a controlled substance have discouraged them.

Meanwhile, even a placebo can be a good thing, Arneson said.

"Is there an expectation effect at work? I'm sure there is, and God bless it, because the whole idea is to try to help improve people's lives by reducing their symptoms."

Minnesota's cannabis products are produced by two companies, LeafLine Labs and Minnesota Medical Solutions. Earlier this week, LeafLine released unpublished survey results of 100 patients showing that 90 percent had used cannabis to reduce pain in 30 days and that 35 percent had cut their opioid usage.