Colon cancer mortality and cannabis use could have a connection, according to a groundbreaking new study from the University of California San Diego.
People who use marijuana may be up to 20 times more likely to die from colon cancer, the study indicates. THC, the active ingredient in cannabis, may cause inflammation in the colon, which causes cancer cells to grow.
“This study raises serious concerns about the potential health risks associated with cannabis use,” says Dr. Rosario Ligresti, chief of Gastroenterology at Hackensack University Medical Center. “While further research is needed to fully understand the underlying mechanisms, these findings underscore the importance of educating the public about the potential dangers of marijuana, particularly in relation to colon cancer.”
Researchers at the University of California San Diego tracked over 1,000 colon cancer patients and compared daily marijuana users to non-users.
The difference was stark — people who used weed daily before their diagnosis had a 56 percent chance of dying within five years of spotting the cancer. That was 11 times higher than those who never touched the drug.
The outlook was even worse for patients who had an official cannabis addiction diagnosis. They were 24 times more likely to die than their peers within five years.
The experts believe THC, the active ingredient in cannabis that causes hallucinogenic effects, may cause inflammation in the colon, which causes cancer cells to grow.
The study analyzed health records of over 1,000 individuals diagnosed with colon cancer. The data revealed a significantly higher mortality rate among those who reported cannabis use. This alarming discovery challenges the unsubstantiated claims of cannabis’s anti-cancer properties, a myth that experts say has circulated for decades.
Consuming cannabis nearly every day increased the risk of dying from colon cancer by up to 20-fold, the research found.
This new research comes on the heels of an increase of cannabis use in the United States, particularly since increasing legalization efforts began. The 2021 National Survey on Drug Use and Health (NSDUH) showed significant increases in past-year marijuana use among adults aged 18 and older compared to previous years.
Experts say this study highlights the urgent need for further research into the link between cannabis use and cancer, as well as the importance of dispelling misinformation surrounding cannabis and its purported health benefits.
In addition to inflammation in the colon being a factor, experts say inflammation may also suppress T cells, a type of white blood cell meant to kill cancer cells.
THC may also block the production of disease-fighting T cells, which normally destroy cancer cells.
Additionally, cannabis use disorder may lead to depression and anxiety, making patients less likely to commit to cancer treatments, the researchers said.
However, just three percent of participants had cannabis use disorder, and it’s unclear what stage their cancers were.
The researchers said more studies are needed to understand how exactly cannabis addiction may increase the risk of colon cancer death.
But the findings come at a critical time: cannabis use among young people has never been higher and a record number of youngsters are developing colon cancer.
According to recent data from the National Survey on Drug Use and Health (NSDUH), 4.5 million young adults aged 18 to 25 in the US reported using cannabis daily or nearly every day.
And of them, eight in 10 daily users met the criteria for cannabis use disorder, indicating problematic patterns of use that can lead to health and social issues.
Research shows that about 18 million Americans of all ages use marijuana daily or nearly everyday. Cannabis use disorder (CUD) is defined as using cannabis every day or nearly every day to the point where it negatively impacts a user’s life, such as making it difficult to hold down a job.
“Inflammation also damages colon tissue over time, causing cells to rapidly form to help repair the destruction,” explains Dr. Ligresti. “The faster cells form, the more likely they are to divide and mutate into cancer cells.”
The research team drew on electronic health records from more than 1,000 colon cancer patients treated across the University of California Health system between 2012 and 2024. They evaluated how cancer outcomes differed based on patients’ documented cannabis use before diagnosis, controlling for age, sex and indicators of disease severity such as tumor staging and cancer biomarkers.
The analysis found:
- 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.