Researchers at the University of California San Diego School of Medicine have discovered a significant link between high cannabis use and poor outcomes in colon cancer patients. According to their study, individuals with a documented history of cannabis use disorder (CUD) were over 20 times more likely to die within five years of a colon cancer diagnosis than those without such a history.
The research, which analyzed electronic health records from more than 1,000 colon cancer patients treated across the University of California Health system between 2012 and 2024, aimed to understand how prior cannabis use might affect cancer prognosis. The team accounted for various factors, including age, sex, tumor stage, and cancer biomarkers, to isolate the impact of cannabis use on survival.
The findings were striking. Patients with CUD had a five-year mortality rate of 55.88%, compared to just 5.05% in patients without CUD. Even after adjusting for other risk factors, individuals with CUD were found to be 24.4 times more likely to die within five years following diagnosis.
These results raise concerns about the broader implications of cannabis use among medically vulnerable populations. While some laboratory studies suggest that certain cannabis compounds may have anti-cancer properties, researchers stress that real-world usage patterns and patient health contexts are far more complex. The growing acceptance and legalization of cannabis use further underline the importance of understanding its health effects, particularly in individuals with serious conditions such as cancer.
"High cannabis use is often linked to depression, anxiety, and other factors that can interfere with a patient’s ability to adhere to treatment plans,” said Dr. Cuomo, a co-author of the study and a member of UC San Diego Moore’s Cancer Center. “This isn’t about condemning cannabis, but about fully understanding how it may influence health outcomes. Our hope is that this work spurs further research and fosters more nuanced discussions about cannabis in cancer care.”
The study ultimately highlights a critical need for deeper investigation into how cannabis affects cancer progression and patient outcomes, urging the medical community to consider these risks when guiding treatment and support strategies.