Cannabis Use Disorder Linked to Risk of Death in Colon Cancer Patients

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Despite often being associated with relief from symptoms associated with certain types of cancer, new research suggests cannabis use could increase risk of death from colon cancer.

A study from the University of California (UC), data indicates patients with cannabis use disorder (CUD) at the time of colon cancer diagnosis experienced a risk of death within the next 5 years that was about 8 to 10 times higher than people without CUD at the time of diagnosis.

“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,” said lead researcher Raphael Cuomo, Ph.D., associate professor in the Department of Anesthesiology at UC San Diego School of Medicine, in a press release.

CUD is a medical condition where a person’s cannabis use causes major problems in daily life, health, or responsibilities, based on criteria from the DSM-5, a manual doctors use to diagnose mental health conditions. Cuomo explained as laws surrounding cannabis use have changed, prevalence of CUD has also increased.

“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,” said Cuomo, who is also a member of UC San Diego Moore’s Cancer Center.

According to a 2022 study conducted among veterans, CUD diagnoses increased from 1.7% to 4.8% in those under 35 between 2005 and 2019. Older groups also showed smaller but steady increases. Rates were higher among individuals with psychiatric disorders, growing from 2.5% to 4.7%.

The study from Cuomo used health records from six University of California hospitals between 2012 and 2024 to analyze how CUD affects survival in people with colon cancer. To be included in the study, patients had to meet several criteria: they needed a confirmed diagnosis of primary colon cancer, a recorded drug use disorder screening before their cancer diagnosis, and available information on cannabis use disorder, age, and gender. Researchers also collected information on cancer severity through tumor stage and a blood test called CEA when available.

In total, 1,088 adults were included in the study. From this group, 34 patients had a history of CUD before they were diagnosed with cancer. The researchers then compared the five-year survival rates between patients with and without CUD.

Findings from the study included:

• Patients with CUD had a five-year death rate of about 56%, while those without CUD had a death rate of about 5%.
• Before adjusting for other health factors, patients with CUD were 24 times more likely to die within five years.
• After adjusting for age, gender, and cancer severity, patients with CUD were still 8 to 10 times more likely to die.
• In long-term follow-up, patients with CUD had a six times higher risk of death compared to those without CUD.

The researchers used advanced statistical methods to fill in missing cancer stage data and made sure cannabis use was identified before the cancer diagnosis. This helped them reduce the chance that cannabis use was a reaction to cancer rather than a factor influencing survival.

“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,” Cuomo added.