A review of medical cannabis use finds little evidence of benefit. Researchers found a chasm between the health reasons for which the public seeks out cannabis and what gold-standard science shows about its effectiveness.
Addiction experts, who studied hundreds of clinical trials, guidelines and surveys conducted over 15 years, found a gulf between how the public perceives cannabis and what gold-standard science shows. Credit…Mohamed Sadek for The New York Times
To treat their pain, anxiety and sleep problems, millions of Americans turn to cannabis, which is now legal in 40 states for medical use. But a new review of 15 years of research concludes that the evidence of its benefits is often weak or inconclusive, and that nearly 30 percent of medical cannabis patients meet criteria for cannabis use disorder.
“The evidence does not support the use of cannabis or cannabinoids at this point for most of the indications that folks are using it for,” said Dr. Michael Hsu, an addiction psychiatrist and clinical instructor at the University of California, Los Angeles, and the lead author of the review, which was published last month in the medical journal JAMA.
For the review, addiction experts at academic medical centers across the country studied more than 2,500 clinical trials, guidelines and surveys conducted mostly in the United States and Canada. They found a wide gulf between the health purposes for which the public seeks out cannabis and what gold-standard science shows about its effectiveness.
The researchers distinguished between medical cannabis, sold at dispensaries, and pharmaceutical-grade cannabinoids — the handful of medicines approved by the Food and Drug Administration with formulations containing either low-grade THC, a psychoactive compound, or CBD, a nonintoxicating compound. Those medicines, including Marinol, Syndros and Cesamet, are available by prescription at conventional pharmacies and have had good results in easing chemotherapy-related nausea, stimulating the appetite of patients with debilitating illnesses like H.I.V./AIDS, and easing some pediatric seizure disorders.
Pain is a leading reason people use medical cannabis, but the review found no evidence to indicate that cannabis could ease acute pain.
Treating chronic, noncancer pain produced more nuanced results. Several medical societies noted by the JAMA authors recommended against using cannabis as a first-line therapy because the evidence of its efficacy was limited.
A desire to sleep is another popular reason that people turn to cannabis and cannabinoids. But the researchers said that sleep trials had also produced weak or inconclusive results, precluding major sleep organizations from making strong recommendations.
But Ryan Vandrey, a Johns Hopkins University professor who helps run its Cannabis Science Lab and was not involved in the JAMA review, said that the return of insomnia can suggest something else: the patient is in cannabis withdrawal.
For anxiety treatment, the new study again showed cannabis’s mixed results. Researchers cited a trial of 80 veterans with PTSD that found no significant difference in outcome among those administered cannabis with a range of dosages of THC and those receiving placebos.
Patients have also tried to treat Parkinson’s disease, glaucoma and rheumatoid arthritis with cannabis, but the researchers said there was insufficient evidence that cannabis or cannabinoids were effective for addressing those medical conditions.
State laws establish whether cannabis can be sold as medicine, for recreation or both. But in practical terms, the paper notes, the baseline ingredients of each type of product are largely indistinguishable, with some variation in dosing and potency. The term “medical cannabis” typically refers to a customer’s reason for using it, rather than indicating something unique about its properties.
There is no national regulation of dispensary cannabis; supervision falls to individual states where it is legal. State standards for labeling, quality control and testing are highly variable and unevenly enforced, regardless of whether a product is promoted for recreational or medical use.
Without reliable monitoring, the JAMA review said, cannabis products sold at dispensaries remain at risk for contamination by mold, pesticides and heavy metals.
The increasing rates of cannabis use disorder was a major impetus for undertaking a review of the research, the researchers said. They pointed to a 2024 meta-analysis that showed that 29 percent of those who used medical cannabis had symptoms of the disorder. Earlier this year, research published in JAMA Psychiatry found that among cannabis users, 34 percent developed such symptoms, which were more frequent and pronounced among those who used the drug for medical rather than recreational reasons.
In the last few years, cannabis products generally have become more potent and more addictive. “That underscores the importance of getting the education right and having better information for both clinicians and patients,” Dr. Hill said.
James P. Randisi, President of Randisi & Associates, Inc., has been helping employers protect their clients, workforce and reputation through implementation of employment screening and drug testing programs since 1999. This post does not constitute legal advice. Randisi & Associates, Inc. is not a law firm. Always contact competent employment legal counsel. To learn more about the rights of employees who test positive for marijuana, Mr. Randisi can be contacted by phone at 410.336.0287 or Email: info@randisiandassociates.com or the website at Randisiandassociates.com
