There is “insufficient evidence” to support most claims for the medical benefits of cannabis and cannabinoids, according to a new study in the Journal of the American Medical Association.
The review of randomized clinical trials published Wednesday also flagged cardiovascular and psychiatric health risks from medical marijuana use, especially when inhaled. It urged doctors to warn patients more clearly of these dangers.
“False claims seem to bolster sales,” Dr. Kevin Hill, an addiction psychiatrist and Harvard Medical School professor who co-wrote the study, said in an email. “While most people are well aware of the risks of alcohol and nicotine, they are not clear about the risks of cannabis.”
Dr. Hill said his findings would surprise the growing number of Americans who believe false advertising claims that marijuana relieves pain and insomnia, which have become the most-cited health reasons for taking it.
The study noted that 27% of U.S. and Canadian adults report having ever used cannabis for medical purposes, reflecting a steady increase as most states have legalized health-related usage since 1996.
Another 10.5% of U.S. residents report using therapeutic cannabidiol, a chemical compound extracted from cannabis that does not produce psychoactive effects.
The analysis of existing research found that people who smoked or vaped marijuana daily for approved medical reasons were more than twice as likely to get heart disease, 1½ times more likely to have a stroke, and slightly more likely to suffer a heart attack.
Researchers also found that 29% of medical marijuana users became addicted to it, creating potential problems for them in work, school or relationships. That’s statistically equal to the 30% of recreational users who become addicts, according to other research.
On the other hand, the study found that evidence “does not support the use of cannabis or cannabinoids for most conditions for which it is promoted, such as acute pain and insomnia.”
Several medical experts not connected to the study said it confirms that physicians should halt recommending medical marijuana until the line between recreation and health uses becomes clearer.
“We simply do not have the data to tell our patients that the benefits outweigh harms for almost every condition written into medical cannabis laws,” said Dr. Andrew Hyatt, a Harvard Medical School psychiatrist who researches marijuana.
He noted that he has treated several patients who developed psychotic disorders after taking medical marijuana for approved reasons, suggesting abuse of state laws and insufficient screening at dispensaries.
In Pennsylvania alone, 17 doctors issued about 132,000 medical marijuana certifications in 2022, or one-third of the state’s total for that year.
“We want to see federal and state laws and regulations that tamp down to zero any medical claims about marijuana and cannabinoids that have not passed the usual process of FDA scrutiny and approval,” said Kevin Sabet, founder of Smart Approaches to Marijuana, an informational nonprofit group.
Keith Humphreys, a Stanford University psychologist and addiction researcher, predicted future studies comparing cannabis to newer treatments for chemotherapy-induced nausea will further weaken the evidence for its medical benefits.
“Overhyped claims of the therapeutic effects of marijuana were cynically advanced by activists to promote legalization,” Mr. Humphreys said. “Even most of them knew their claims were somewhere between inflated and entirely made up.”
Marijuana advocates said the study underscores the need to legalize cannabis federally, making it easier to standardize medical research and treatments.
“The cannabis sector is still developing the research infrastructure that most industries take for granted,” said Destinee Blanco, president of the Marijuana Industry Trade Association. “Studies like this should be treated as a call for more data, not a dismissal of current progress.”
“The study saying ‘insufficient evidence’ is not the same as ‘doesn’t work,’” added Jerry Joyner, a Texas-based marijuana advocate. “It means we haven’t been allowed to study it properly.”
Coleman Drake, a University of Pittsburgh public health professor who researches recreational marijuana laws, noted that anecdotal reports and a 2017 federal study still insist that cannabis can be effective for relieving chronic neuropathic pain.
“It is rare that people obtain approval to use medical cannabis from their regular primary care provider,” Mr. Drake said. “They may not tell their primary care provider that they are using it.”
According to doctors, the study suggests it’s time to remind people that cannabis remains a dangerous drug, especially for those who inhale marijuana smoke daily.
“People are using medical claims to justify utilization for recreational purposes, and assuming that since there are medical benefits in some cases, the overall risks are not significant,” said Dr. Craig Escude, a family physician and fellow of the American Academy of Developmental Medicine.
Weighing the risks
In the study published Tuesday, cannabinoids fared slightly better than psychoactive cannabis.
The Food and Drug Administration has approved cannabinoids for the treatment of pediatric seizures, HIV/AIDS-related anorexia, and chemotherapy-induced nausea and vomiting.
The study’s authors noted that clinical trials “reported a small but significant reduction in nausea and vomiting” from prescribed cannabinoids such as dronabinol and nabilone, compared with placebos and other drugs.
Patients with HIV/AIDS also experienced moderate weight gain from taking cannabinoids, compared with a placebo.
“Beyond the indications for which we have FDA-approved cannabinoids, the evidence for cannabis as a treatment for other medical conditions is limited,” said Dr. Hill, the study’s lead author. “Medical cannabis is definitely used in far more clinical situations than the evidence warrants.”
While doctors may write prescriptions for cannabinoids, cannabis remains illegal under federal law.
In states with medical cannabis policies, physicians write a certification for its medical use, allowing patients to buy it directly from dispensaries.
The study also warned that cannabis, which has increased in potency in recent decades, could have damaging psychiatric effects on patients. That includes potentially worsening the mental health of pregnant, schizophrenic, and heart disease patients.
The study found that 12.4% of patients using high-potency cannabis developed psychotic symptoms, compared to 7.1% of low-potency users.
Another 19.1% of high-potency users reported generalized anxiety disorder, compared with 7.1% of low-potency users.
The study said patients should avoid using medical marijuana simultaneously with “alcohol or other central nervous system depressants such as benzodiazepines,” use “the lowest effective dose,” and abstain from use “when driving or operating machinery.”
• Sean Salai can be reached at ssalai@washingtontimes.com.
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