High Cannabis Use May Be Connected to Increased Mortality Seen in Colon Cancer Patients

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According to a recent study conducted by the University of California San Diego School of Medicine (San Diego, California), researchers saw that colon cancer patients who had a documented history of high cannabis use “were more than 20 times more likely to die within five years of diagnosis compared to those without such a history,” (1,2).

“This study adds to a growing body of evidence suggesting that heavy cannabis use may have underrecognized impacts on the immune system, mental health and treatment behaviors — all of which could influence cancer outcomes,” lead author Raphael Cuomo, Ph.D., associate professor in the Department of Anesthesiology at UC San Diego School of Medicine and a member of UC San Diego Moore’s Cancer Center, commented (1).

To gather data, researchers gathered and analyzed more than 1,000 colon cancer patients electronic health records that received treatment in the University of California Health system between 2012 to 2024 (1,2). With these records, the cancer outcomes of these patients were reviewed on “patients’ documented cannabis use before diagnosis, controlling for age, sex and indicators of disease severity such as tumor staging and cancer biomarkers,” (1).

UC San Diego Today reported that the analysis found (1):

• Patients with a history of cannabis use disorder (CUD) had a substantially higher five-year mortality rate (55.88 %) compared to patients without CUD (5.05 %).
• Patients diagnosed with CUD prior to cancer diagnosis were 24.4 times more likely to die within five years of diagnosis compared to those without CUD.

“High cannabis use is often associated with depression, anxiety and other challenges that may compromise a patient’s ability to engage fully with cancer treatment,” Cuomo said (1). “However, this isn’t about vilifying cannabis. It’s about understanding the full range of its impacts, especially for people facing serious illnesses. We hope these findings encourage more research — and more nuanced conversations — about how cannabis interacts with cancer biology and care.”

References

1. Martin, M. High cannabis use linked to increased mortality in colon cancer patients https://today.ucsd.edu/story/high-cannabis-use-linked-to-increased-mortality-in-colon-cancer-patients (accessed Apr 30, 2025).
2. Cuomo, R.E., Cannabis use disorder and mortality among patients with colon cancer, Annals of Epidemiology,2025, 106, Pages 8-10, ISSN 1047-2797, https://doi.org/10.1016/j.annepidem.2025.04.012.