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Medical cannabis might be a helpful therapy for some people who have chronic pain, but it’s unlikely to benefit most, according to new clinical guidelines published Wednesday in the journal BMJ.

The guidelines, crafted by an international group of researchers who analyzed three dozen medical cannabis studies, say there isn’t enough evidence that medical marijuana products help most patients suffering from chronic pain, so they shouldn’t be widely recommended for such people.

“When we look at the overall evidence for therapeutic cannabis products, the benefits are quite modest,” said lead author Jason Busse, associate director of McMaster University’s Michael G. DeGroote Centre for Medicinal Cannabis Research in Ontario.


Even as medical marijuana has been legalized in 36 U.S. states and Washington, D.C., health care providers and patients have had little guidance on when it’s appropriate to use, especially for chronic pain. Busse and his team set out to fill that gap, but found a limited pool of studies that met their criteria because of federal restrictions that make it difficult to research medical uses of cannabis.

Because of the limited data, the guidelines do not recommend the medical use of smoked or vaped marijuana. In analyzing the available research, Busse’s team found that only small percentages of participants reported “an important improvement” in chronic pain, physical function, or sleep quality while taking oral or topical cannabis treatments.


“So medical cannabis is not likely to be a panacea. It is not likely to work for the majority of individuals who live with chronic pain. We do have evidence that it does appear to provide important benefits for a minority of individuals,” said Busse, who is also a chiropractic doctor.

The guidelines advise clinicians to cater to the specific needs of their patients, and start with non-inhaled CBD products before adding THC or other mind-altering compounds into the mix. THC is one of the ingredients in cannabis that causes a feeling of being high, but it can also cause dizziness or other side effects that might be deal-breakers for some patients.

The patient experience is a central focus of the new recommendations. In an unusual move, several “patient partners,” including former and current cannabis users, helped develop the guidelines. Busse’s center paid for developing the guidelines, and he selected the panel of experts, who were screened to ensure none had a financial interest in cannabis companies. None of the center’s funding comes from the cannabis industry, Busse said.

More research needed to guide patients

Busse hopes the paper can help clear up some of the confusion surrounding the use of medical marijuana as an analgesic, but even his guidelines contain ample gray area. Many questions remained unanswered due to a dearth of meaningful research, he said:

  • Is medical cannabis safe and effective for some children, veterans, and/or people with mental health disorders?
  • Is there a difference in how cancer patients and non-cancer patients with chronic pain respond to medical marijuana?
  • Can medical cannabis help opioid users with chronic pain taper off these drugs?
  • Do the potential risks associated with inhaling cannabis products, including lung damage, outweigh the possible benefits?

Patients have legitimate, complex reasons for wanting to try or stay away from medical cannabis, Busse said. While some people with severe chronic pain might be willing to use medical marijuana in hopes of getting even a slight bit of relief, other patients could be fine managing their pain with the standard of care and don’t want to endure potentially negative side effects.

Even when a patient decides to try medical cannabis, there are so many products, formulations, and varieties to choose from, but no definitive information on which components are most effective at treating certain symptoms.

Part of the reason for that is because much of what is on the market is a blend, unlabeled, and goes unregulated by the Food and Drug Administration, said Judith A. Paice, director of the Cancer Pain Program at Northwestern University’s Feinberg School of Medicine.

Paice, an oncology nurse, was the lead author of a set of 2016 guidelines for managing chronic pain in cancer survivors. At the time, Paice and her panel wrote there was “insufficient evidence” to recommend medical cannabis for cancer survivors with chronic pain. That hasn’t changed, despite the advances in our understanding of cancer treatment and cannabis since 2016, she told STAT.

Since cannabis is classified in the U.S. as a Schedule I Controlled Substance — the same designation given LSD and heroin — the National Institutes of Health’s “hands have been tied” when it comes to funding research on medical cannabis, Paice said.

Smoked and vaped marijuana excluded

Smoked and vaped forms of medical marijuana have not been rigorously studied when it comes to the management of chronic pain, but patients and clinicians continue to turn to inhaled products, Busse said.

“So there appears to be the potential of a rather substantial disconnect out there with respect to what patients are currently using … and what the evidence would currently support,” he said.

Karen O’Keefe, director of state policies for the Marijuana Policy Project, said clear clinical guidelines are helpful, but they would be more realistic if they included inhaled cannabis. MPP advocates for the legalization of medical marijuana in the U.S.

The exclusion of inhaled cannabis was “unfortunate,” O’Keefe told STAT, because “there are a lot of patients that use cannabis inhalation” and can get immediate, appropriately-dosed relief instead of waiting for the delayed effects that come from using edibles or other forms.

“And in reality, people are going to most likely continue to use [inhaled] cannabis — from the streets, in some cases — if that’s what works best for them,” she said.

Even inhaled cannabis, which many clinicians consider riskier than non-smoked marijuana products, is safer than opioids and other therapies people are using to manage chronic pain, O’Keefe argued.

Of the three dozen studies analyzed by Busse’s group, 21 were funded by the cannabis industry, but he said the researchers didn’t find any important differences between trials with and without industry support.

For Busse, the guidelines’ limitations underline the need for additional research on medical cannabis. Although medical marijuana has shown some promise and cannot be fatally overdosed, he wants to avoid “repeating history.”

“We spent how many decades without good evidence, increasingly promoting and prescribing opioids for chronic pain, only to realize that the benefits were less than we thought and the harms were greater than we thought,” he said. “And now there’s this struggle to sort of try to move into a different direction, and I think unless we’re cautious, we might end up repeating the same story, but with medical cannabis.”

Isabella is the inaugural recipient of the Sharon Begley-STAT Science Reporting Fellowship.

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