Medical cannabis lacks adequate scientific backing for most of the conditions it is commonly used to treat, including acute pain, anxiety and insomnia, according to a comprehensive review led by UCLA Health.
The paper, published in JAMA, reviewed more than 2,500 articles published from January 2010 through September 2025 including randomized clinical trials, meta-analyses and clinical guidelines. More than 120 studies were prioritized based on their large samples, recency, topics covered and relevancy.
The findings come as medical uses for cannabis and cannabinoids such as CBD have grown in popularity, with 27% of people in the U.S. and Canada having reported using it for various purposes such as pain relief, anxiety and sleep problems, according to a 2018 survey.
Dr. Michael Hsu, the review’s first author and health sciences clinical instructor at the UCLA Health Department of Psychiatry and Biobehavioral Sciences, said, “In medical training, we just don't receive extensive education on the topic of medical cannabis. Many physicians lack comprehensive training on its benefits, risks and proper dosages, leading to confusion, and, at times, avoidance of the conversation altogether.”
The review confirmed that pharmaceutical-grade cannabinoids approved by the U.S. Food and Drug Administration have demonstrated effectiveness but only in a narrow range of conditions. These include medications for HIV/AIDS-related appetite loss, chemotherapy-induced nausea and vomiting and certain severe pediatric seizure disorders such as Dravet syndrome and Lennox-Gastaut syndrome. The review also highlighted that there is some evidence to suggest that cannabinoids may be beneficial for spasticity patients with multiple sclerosis and certain forms of chronic pain, such as neuropathic pain. For most other conditions, the evidence remains either inconclusive or lacking, the review found.
When asked why many people are convinced that they benefit from cannabis for treating medical conditions not supported by evidence, Hsu said, “In some cases, this could be because there aren’t enough studies to determine its benefits, even if they exist. In other cases, cannabis may provide short-term relief but may not be addressing the underlying condition; in fact, it may worsen it or impede engagement in other treatments like physical therapy or psychotherapy.
“For some conditions, our research found evidence that cannabis was not effective,” Hsu continued. “However, it is important to acknowledge that presenting facts or evidence alone is not a substitute for recognizing patients’ humanity and lived experiences. Being with patients and understanding their stories is crucial in providing evidence-based recommendations and addressing their underlying conditions.”
The review also highlighted potential health risks associated with cannabis use. Longitudinal data from adolescents indicated that high-potency cannabis may be linked to increased rates of psychotic symptoms (12.4% versus 7.1% for low-potency) and generalized anxiety disorder (19.1% versus 11.6%).
About 29% of people who use medical cannabis also met criteria for cannabis use disorder. Daily use of cannabis, particularly use of inhaled and/or high-potency products, may be associated with cardiovascular risks, including higher rates of coronary heart disease, heart attack and stroke compared to non-daily use.
The review emphasizes that clinicians should carefully screen patients for cardiovascular disease and psychotic disorders, evaluate potential drug interactions and assess whether the risks outweigh the benefits before considering THC-containing products for medical purposes.
“Patients deserve honest, non-judgmental conversations about what the science does and doesn't tell us about medical cannabis,” Hsu said.
The authors noted several limitations of the review. The paper was not a systemic review, and it did not conduct a formal risk of bias assessment of the included studies. Several studies in the review were observational and may be subject to confounding. Additionally, recommendations from clinical trials may not apply to all patients due to variations in their design, patient characteristics and cannabis products tested.
“Further research is crucial to better understand the potential benefits and risks of medical cannabis. By supporting more rigorous studies, we can provide clearer guidance and improve clinical care for patients,” said Hsu.
Researchers from Harvard, UC San Francisco, Washington University School of Medicine, and New York University contributed to the study.
