The utility of cannabinoids to treat most medical conditions remains uncertain at best, but for at least three indications the data lean in favor of effectiveness, Ellie Grossman, MD, MPH, told attendees recently at the 2024 American College of Physicians Internal Medicine.
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Those are neuropathic pain, chemotherapy-induced nausea or vomiting, and spasticity in people with multiple sclerosis, said Grossman, an instructor at Harvard Medical School in Boston, Massachusetts, and medical director for primary care/behavioral health integration at Cambridge Health Alliance in Somerville, Massachusetts.
Dearth of Research Persists
Research is sorely lacking and of low quality in the field for many reasons, Grossman said. Most of the products tested come from outside the United States and often are synthetic and taken orally — which does not match the real-world use when patients go to dispensaries for cannabis derived directly from plants (or the plant product itself). And studies often rely on self-report.
Chronic pain is by far the top reason patients say they use medical cannabis, Grossman said. A Cochrane review of 16 studies found only that the potential benefits of cannabis may outweigh the potential harms for chronic neuropathic pain.
No Evidence in OUD
Grossman said she is frequently asked if cannabis can help people quit taking opioids. The answer seems to be no. A study published earlier this year in states with legalized medical or recreational cannabis found no difference between rates of opioid overdose compared with states with no such laws. "It seems like it doesn't do anything to help us with our opioid problem," she said.
Nor does high-quality evidence exist showing use of cannabis can improve sleep, she said. A 2022 systematic review found fewer than half of studies showed the substance useful for sleep outcomes. "Where studies were positives, it was in people who had chronic pain," Grossman noted. Research indicates cannabis may have substantial benefit for chronic pain compared with placebo.
Potential Harms
If the medical benefits of cannabis are murky, the evidence for its potential harms, at least in the short term, are clearer, according to Grossman. A simplified guideline for prescribing medical cannabinoids in primary care includes sedation, feeling high, dizziness, speech disorders, muscle twitching, hypotension, and several other conditions among the potential hazards of the drug.
But the potential for long-term harm is uncertain. "All the evidence comes from people who have been using it for recreational reasons," where there may be co-use of tobacco, self-reported outcomes, and recall bias, she said. The characteristics of people using cannabis recreationally often differ from those using it medicinally.
Use With Other Controlled Substances
Grossman said clinicians should consider whether the co-use of cannabis and other controlled substances, such as benzodiazepines, opioids, or Adderall, raises the potential risks associated with those drugs. "Ultimately it comes down to talking to your patients," she said. If a toxicity screen shows the presence of controlled substances, ask about their experience with the drugs they are using and let them know your main concern is their safety.
Grossman reported no relevant financial conflicts of interest.
Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News, Northwestern magazine and Nurse.com and was an editor at the Chicago Sun-Times, Cincinnati Enquirer, and St. Cloud Times. Follow her on X @MLfrellick.
