Major cannabis study finds little proof for popular medical claims, flags big dangers

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Cannabis has been linked to some significant medical benefits, but recent research calls those into question.

A major new analysis published in JAMA examined more than 2,500 scientific papers from the last 15 years, including other reviews, clinical trials and guidelines focused on medical marijuana.

"While many people turn to cannabis seeking relief, our review highlights significant gaps between public perception and scientific evidence regarding its effectiveness for most medical conditions," Dr. Michael Hsu of University of California – Los Angeles (UCLA) Health Sciences, author of the study, said in a press release.

Many medical claims about cannabis are not supported by strong scientific evidence, according to a comprehensive review published in JAMA. (iStock)

The researchers — led by UCLA with contributions from Harvard, UC San Francisco, Washington University School of Medicine and New York University — set out to determine how strong the research is on the effectiveness of medical cannabis and to offer evidence-based clinical guidance.

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The review found that evidence supporting most medical uses of cannabis or cannabinoids is limited or insufficient, the release stated.

"Whenever a substance is widely used, there is likely to be a very wide set of outcomes," Alex Dimitriu, MD, double board-certified in Psychiatry and Sleep Medicine and founder of Menlo Park Psychiatry & Sleep Medicine, told Fox News Digital.

"Cannabis is now used by about 15 to 25% of U.S. adults in the past year, for various reasons ranging from recreational to medicinal. This study points to the reality that this widely used substance is not a panacea," said Dimitriu, who was not involved in the study.

There are very few conditions for which cannabinoid therapies have clear, well-established benefits backed by high-quality clinical data, according to the researchers.

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The strongest evidence supports FDA-approved cannabinoid medications for treating specific conditions, including HIV/AIDS-related appetite loss, chemotherapy-induced nausea and vomiting, and certain severe pediatric seizure disorders.

The review identified significant safety concerns, with high-potency cannabis use among young people linked to higher rates of mental health issues. (iStock)

For many other conditions that are commonly treated with cannabis — such as chronic pain, insomnia, anxiety or post-traumatic stress disorder — evidence from randomized trials did not support meaningful benefit.

The analysis also examined safety concerns — in particular, how young people using high-potency cannabis may be more likely to suffer higher rates of psychotic symptoms and anxiety disorder.

Daily inhaled cannabis use was also linked to increased risks of coronary heart disease, myocardial infarction (heart attack) and stroke when compared with non-daily use.

Daily inhaled cannabis use is associated with increased cardiovascular risks, including coronary heart disease, heart attack and stroke. (iStock)

Based on these findings, the review emphasizes that clinicians should weigh potential benefits against known risks when discussing cannabis with patients.

The authors suggest that clinicians screen patients for cardiovascular risk, evaluate mental health history, check for possible drug interactions and consider conditions where risks may outweigh benefits.

They recommend open, realistic conversations and caution against assuming that cannabis is broadly effective for medical conditions.

The review highlights the need for caution, urging clinicians to weigh risks, screen patients appropriately and avoid assuming cannabis is broadly effective. (iStock)

"Patients deserve honest conversations about what the science does and doesn't tell us about medical cannabis," Hsu said.

This article is a narrative review rather than a systematic review, so it did not use the strict, standardized methods that help reduce bias in how studies are selected and evaluated, the researchers noted.

The review notes further limitations, including that some evidence comes from observational research rather than randomized trials, which means it cannot establish cause and effect.

The trial results also may not apply to all populations, products or doses.