A groundbreaking analysis recently published in the journal Frontiers in Oncology brings to light strong scientific evidence in favor of medicinal cannabis, both as a treatment for cancer symptoms and as a potential weapon against the progression of the disease itself.
The study, led by Ryan Castle, director of research at the Whole Health Oncology Institute, aimed to identify a scientific consensus around the use of cannabis in cancer – an area until recently fragmented by conflicting and isolated studies. Due to the fact that cannabis remains a Schedule I substance in the US, the conduct of clinical research has been limited until now.
To overcome this challenge, the research team analyzed more than 10,000 studies, a number ten times larger than any previous meta-analysis in the field. Using artificial intelligence techniques, specifically sentiment analysis, they classified the studies according to their attitude toward medical cannabis: positive, neutral, or negative.
The results were impressive: 75% of the studies reached conclusions that supported the effectiveness of medical cannabis. In addition to clearly relieving symptoms such as loss of appetite, nausea, inflammation, and pain, a significant percentage of studies highlighted cannabis’ ability to induce apoptosis (the natural death of cancer cells) and inhibit the spread of tumors.
Castle said his team had expected a modest consensus of around 55%. The fact that 75% of the studies supported the therapeutic use of cannabis was a “shocking level of consensus” for such a controversial public health issue.
However, medical cannabis is not without its challenges. A 2024 meta-analysis published in the journal JAMA found that adults with cannabis use disorder had an increased risk of head and neck cancer. Dr. Donald Abrams, an oncologist at the University of California, San Francisco, said the study was methodologically flawed because it did not adequately account for the frequent combination of cannabis use with tobacco and alcohol—known carcinogens.
Abrams himself acknowledges cannabis’s value in relieving cancer symptoms, but remains skeptical about its anticancer properties in humans. However, he admits that there is “elegant” preclinical evidence in test tubes and animal models that cannabinoids can affect the growth of cancer cells and tumors.
Examples from early clinical trials are encouraging. In a pilot study of 21 cancer patients, those who received medicinal cannabis along with chemotherapy survived longer than those who received a placebo alone. In another study of 119 patients, the use of synthetic CBD was associated with a reduction in tumor size and the circulation of cancer cells in the blood.
While this evidence is promising, scientists agree that larger, rigorously designed human clinical trials are needed to confirm the effects and determine the optimal forms and dosages of treatment.
The research team hopes that this review will pressure relevant authorities, such as the US Drug Enforcement Agency (DEA), to proceed with the declassification of cannabis, facilitating scientific research and its safe use in oncology.
“We are not asking for the criteria for approving cancer treatments to be relaxed,” Castle said. “We are arguing that medicinal cannabis meets or exceeds those standards – often to a greater extent than many current pharmaceutical treatments.”