Study Reveals Weaknesses in the Evidence Supporting Medical Cannabis

The authors of this comprehensive review concluded that medical cannabis lacks sufficient scientific backing for most of the conditions for which it is commonly used. However, some experts believe the study may not present a complete picture of the available evidence.

Published in the journal JAMA, the paper was led by researchers at UCLA Health and examined over 2,500 articles published from January 2010 to September 2025, including randomised trials, meta-analyses, and clinical guidelines. More than 120 studies were prioritised based on their large sample sizes, relevance, and other important factors.

What did the Review Show?

The review confirmed that FDA-approved pharmaceutical-grade cannabinoids have shown effectiveness, but only for a limited number of conditions. These conditions include treatments for appetite loss related to HIV/AIDS, nausea and vomiting caused by chemotherapy, and severe pediatric seizure disorders like Dravet syndrome and Lennox-Gastaut syndrome.

For most other conditions, such as chronic pain, anxiety, and insomnia, the evidence is either uncertain or lacking altogether. Despite over half of medical cannabis users reporting its use for chronic pain, current guidelines do not recommend cannabis-based medicines as a first-line treatment for this condition.

Dr Michael Hsu, the lead author of the review from UCLA Health, highlighted the disconnect between public perceptions and the latest scientific research regarding the medical benefits of cannabis.

"Many people turn to cannabis for relief, but our review shows large gaps between what the public believes and what the scientific evidence supports regarding its effectiveness for most medical issues," Dr Hsu explained. He emphasised the importance of clear guidance from healthcare professionals to help patients make informed decisions about medical cannabis.

The review also pointed out potential health risks associated with cannabis use, stressing that healthcare providers should carefully screen patients for cardiovascular issues and mental health disorders, as well as evaluate potential drug interactions before recommending THC-containing products.

What Are the Limitations of the Review?

The authors acknowledged some limitations in their review, including the absence of a formal assessment of bias in the included studies. Many of the studies analysed were observational and varied widely in design and patient demographics.

However, some experts raised additional concerns about the quality of the research findings. Dr Simon Erridge, Director of Research at Curaleaf Clinic and co-author of many peer-reviewed studies on medical cannabis, expressed worries about the transparency of the study selection process and the review's tendency to focus on negative outcomes.

"The recent JAMA review of therapeutic cannabis provides an overview of current evidence, but I have concerns about the clarity of how studies were chosen for inclusion," Dr Erridge stated. He noted that the methodology was unclear regarding why some studies were included while others with similar findings were excluded.

In 2023, the BMJ published a comprehensive review that examined similar evidence. While both reviews reached comparable conclusions about the effectiveness of cannabidiol for epilepsy and the use of cannabis-based medicines for conditions like multiple sclerosis and chronic pain, Dr Erridge pointed out that the BMJ authors used clearer methods.

The BMJ review presented the evidence in a more balanced way, clearly acknowledging both risks and benefits for readers. Dr Erridge concluded, "Both healthcare professionals and patients deserve access to balanced information that doesn't exaggerate benefits or amplify concerns unnecessarily. Sadly, this article does not meet that standard." Researchers agree that there is still a pressing need for high-quality, long-term studies on medical cannabis.

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