Medical Cannabis Lacks Strong Scientific Evidence for Most Common Uses, Major JAMA Review Finds

Medical cannabis has become a popular option for people looking to manage pain, anxiety, sleep problems, and a wide range of other health conditions. But a new and extensive scientific review suggests that the evidence supporting these uses is far thinner than many people realize.

Researchers from UCLA Health, along with collaborators from Harvard, UC San Francisco, Washington University School of Medicine, and New York University, conducted a large-scale review of medical cannabis research. Their findings were published in The Journal of the American Medical Association (JAMA) and paint a much more cautious picture of cannabis as a medical treatment than public perception often suggests.

A massive review of more than a decade of research

The research team examined over 2,500 scientific studies published between January 2010 and September 2025. These included randomized clinical trials, meta-analyses, observational studies, and clinical guidelines. From this pool, more than 120 studies were given priority based on factors such as sample size, relevance, recency, and study quality.

The goal of the review was simple but ambitious: to assess what the science actually says about the therapeutic use of cannabis and cannabinoids, including THC and CBD, across a wide range of medical conditions.

The results reveal a clear pattern. While cannabis is widely used and often perceived as helpful, solid scientific backing exists for only a small number of medical applications.

Where medical cannabis does show clear benefits

The review confirmed that FDA-approved, pharmaceutical-grade cannabinoid medications do have proven effectiveness, but only for a narrow set of conditions. These include:

• Loss of appetite related to HIV/AIDS
• Nausea and vomiting caused by chemotherapy
• Severe pediatric seizure disorders, such as Dravet syndrome and Lennox-Gastaut syndrome

In these cases, the benefits are supported by high-quality clinical trials using standardized, regulated formulations, not general cannabis products available through dispensaries.

This distinction is important. The review makes it clear that evidence for specific FDA-approved drugs cannot be automatically applied to smoked cannabis, edibles, or unregulated CBD products.

Popular uses don’t match the science

Despite limited evidence, medical cannabis is frequently used for conditions such as chronic pain, anxiety, and insomnia. Surveys show that more than half of medical cannabis users rely on it for chronic pain alone, and overall, about 27% of people in the U.S. and Canada reported using cannabis for medical purposes in a widely cited 2018 survey.

However, the review found that for most of these common uses, the evidence is either inconsistent, inconclusive, or simply lacking. Current clinical guidelines do not recommend cannabis-based medicines as a first-line treatment for chronic pain, even though pain relief is one of the most common reasons people seek medical cannabis.

The researchers emphasize that there is a significant gap between public perception and scientific evidence, which can lead to unrealistic expectations and potentially risky choices.

Health risks that deserve more attention

Beyond limited effectiveness, the review highlights several potential health risks associated with cannabis use, especially when used frequently or in high-potency forms.

One area of concern is mental health, particularly among adolescents and young adults. Long-term data suggest that people using high-potency cannabis experience higher rates of:

• Psychotic symptoms (about 12.4% compared to 7.1% among users of low-potency products)
• Generalized anxiety disorder (around 19.1% versus 11.6%)

Another major issue is cannabis use disorder. The review estimates that roughly 29% of people using medical cannabis meet criteria for this condition, raising concerns about dependency even when cannabis is used for health-related reasons.

Cardiovascular concerns are growing

Daily cannabis use, especially inhaled or high-THC products, may also pose cardiovascular risks. The review links regular use to higher rates of coronary heart disease, heart attacks, and strokes compared with non-daily users.

Because of these risks, the researchers advise clinicians to carefully screen patients before recommending THC-containing products. This includes evaluating:

• Cardiovascular disease history
• Psychotic or mood disorders
• Potential drug interactions
• Overall risk-versus-benefit balance

Why clearer medical guidance is needed

One of the key messages from the review is that patients often turn to cannabis without clear, evidence-based guidance. Many assume that because cannabis is natural or widely accepted, it must be safe and effective.

The researchers argue that clinicians play a crucial role in correcting misconceptions and helping patients make informed decisions. Honest conversations about what science supports and where uncertainty remains are essential, especially as cannabis products become more potent and more accessible.

Important limitations of the review

While comprehensive, the review does have limitations. It was not a formal systematic review, and the researchers did not conduct a full risk-of-bias assessment for every included study. Many of the analyzed studies were observational, meaning they may be influenced by confounding factors.

Additionally, results from specific trials may not apply to all patients, since cannabis products, dosages, delivery methods, and patient characteristics vary widely.

Even so, the authors stress that the overall pattern is consistent: robust evidence is the exception, not the rule, when it comes to medical cannabis.

Why studying cannabis is so challenging

Research on cannabis faces unique obstacles. Variability in THC and CBD concentrations, differences in consumption methods, and legal restrictions have historically made high-quality clinical trials difficult to conduct. Unlike conventional medications, cannabis is not a single standardized compound, which complicates study design and interpretation.

This complexity partly explains why evidence remains limited, despite widespread use.

What future research needs to focus on

The review strongly calls for more rigorous, well-designed clinical trials. Researchers need to better define:

• Which conditions may genuinely benefit from cannabinoids
• Optimal dosages and formulations
• Long-term safety risks
• Differences between THC-dominant and CBD-dominant products

Only with stronger evidence can clinicians provide clearer, safer, and more consistent guidance to patients.

The takeaway

Medical cannabis is often viewed as a versatile solution for many health problems, but the latest scientific review suggests that its proven benefits are far more limited than popular belief. While certain FDA-approved cannabinoid medications are effective for specific conditions, most common uses lack strong scientific support and carry meaningful risks.

As cannabis continues to move into the medical mainstream, evidence—not enthusiasm—will need to guide its role in healthcare.

Research paper reference:
https://jamanetwork.com/journals/jama/fullarticle/10.1001/jama.2025.19433