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Enrollment in medical cannabis programs across the U.S. jumped by over four times between 2016 and 2020, according to a new study that also examined the qualifying conditions patients list on their licensing forms.

Researchers found increasing enrollment was clustered in states with medical-only cannabis programs, while enrollment in states that also permit recreational use declined or stagnated between 2016 and 2020. The researchers identified chronic pain as the most commonly listed condition specified on medical license applications.


Most studies on cannabis use look at adult use overall, without separating out medical cannabis enrollment, said lead author Kevin Boehnke, a chronic pain researcher at the University of Michigan. He said he wanted to fill that gap.

Boehnke said he kept asking himself, “How many people are using cannabis for pain? Why are people actually using [medical cannabis]?”

Thus began a multi-year investigation into medical cannabis enrollment across the U.S. Boehnke gathered the data piece by piece from publicly available reports on state websites, meeting notes, state officials, and documents obtained via Freedom of Information Act requests.


He said his aim was to keep tabs on medical use of cannabis at a time when laws governing it are quickly changing. “These changing state policies have dramatic effects on how many people might be using cannabis for medical purposes or how they might be able to do so,” said Boehnke, who published a 2019 study on the issue as well.

Bryon Adinoff, a psychiatrist, drug addiction researcher, and president of Doctors for Cannabis Regulation, was reassured by the results showing that medical cannabis use is increasing in the U.S. He said he hopes the new study will highlight the importance of cannabis as a medical treatment.

Doctors have hesitated prescribing cannabis for decades. Adinoff himself said he was wary of the medical benefits of cannabis when he first began practicing medicine in the 1980s. But his views have evolved.

“I didn’t really buy into it, but, you know, after you talk to several hundred people who have benefited from it, you start to think maybe there’s something to it,” he said.

That’s why Adinoff said it is important this study was published in the Annals of Internal Medicine. “Hopefully it will get organized medicine and physicians individually to pay increasing attention to this issue,” he added.

While most medical-only states showed a steady uptick in patient enrollment, Oklahoma experienced a substantial jump. Now, one in 10 Oklahoma residents are licensed medical cannabis patients. Oklahoma does not require patients to have specific medical conditions that qualify for enrollment. Instead, they can seek medical cannabis cards for any condition, leaving it up to the physician to decide if cannabis may help.

Other states have strict lists of qualifying conditions; chronic pain appears on most, which may explain why it’s the most prevalent qualifying condition, topping the list at 60%.

Silvia Martins, an epidemiologist at Columbia University specializing in substance use, said patients and doctors may be more willing to try cannabis to alleviate chronic pain because it’s one of the few conditions backed by evidence-based research showing cannabis can help. “Even for chronic pain, we need more evidence, but for other types of conditions, we need even more evidence,” she said. Chronic pain patients, Martins added, also happen to be targeted often with cannabis ads.

Experts say the fact that medical cannabis enrollment is flatlining or declining in recreational use states shouldn’t be interpreted to mean medical use is on the wane. Stuart Smith, co-director of cannabis advocacy for the U.S. Pain Foundation, said cannabis users may simply be self-medicating in recreational states.

“The driving force is cost,” Smith said. Enrollment in medical cannabis programs requires a visit to a doctor and a processing fee. In recreational states, adults can show their drivers license and walk through the door. Smith said recreational use laws help keep patients from going to the black market for cannabis where they do not know what they are getting.

Yet, recreational use laws that do not include separate provisions for medical cannabis use limit the doses, types of cannabis products or strains medical patients may need for medication. “Please don’t put us together under the same umbrella. We’re not the same,” said Ellen Lenox Smith, the other co-director of cannabis advocacy for the U.S. Pain Foundation.

Adinoff said he worries about self-medication, and wishes cannabis patients still sought medical advice even when living in recreational states. “These are potent drugs and if people have significant medical problems, they should be taking it under the care of a physician who knows what they’re doing,” he said.

But the greatest need, Adinoff says, is more research.

Boehnke’s study found the proportion of medical cannabis patients listing conditions not supported by “substantial” evidence, according to National Academies of Sciences, Engineering, and Medicine standards, increased between 2016 and 2020. However, it doesn’t mean the medical conditions could not benefit from cannabis, Boehnke says. The studies just have not been done.

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