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• Posted August 1, 2025

Heavy Weed Use Brings High Risk for Oral Cancers

Folks who smoke a lot of marijuana could be facing a more than four-fold odds of developing an oral cancer, new research suggests.

“Cannabis smoke contains many of the same carcinogenic compounds found in tobacco smoke, which have known damaging effects on the epithelial tissue that lines the mouth," noted study lead author Raphael Cuomo, associate professor of anesthesiology at UC San Diego School of Medicine. 

As with any smoked product, over time this ongoing cellular damage can give rise to cancer, he said.

The findings were published in the September 2025 issue of the journal Preventive Medicine Reports.

The study focused on people with daily or near-daily use of the drug, which can develop into what clinicians call cannabis use disorder. More than 17.7 million Americans reported this level of use in 2022, according to the study.

In the study, Cuomo and team tracked the electronic health records of more than 45,000 patients, of whom 949 were diagnosed with cannabis use disorder. 

Even after adjusting for other oral cancer risk factors, such as age or cigarette smoking, people with cannabis use disorder had a 325% higher odds of developing some form of oral cancer over a five-year period, compared to folks who didn’t have the disorder.

Adding cigarettes into the mix upped the odds even higher: People who smoked a lot of weed plus cigarettes had a 624% higher risk of oral cancer, compared to people who didn’t have cannabis use disorder, Cuomo’s team found. 

Based on the findings, researchers suspect that more than simply smoke exposure may be driving the high oral cancer risk in people who use a lot of weed. It’s possible, they say, that the THC in marijuana might be suppressing the immune system, leaving people more vulnerable to cancer.

Whatever the reasons, the findings “add to a growing body of evidence suggesting that chronic or problematic cannabis use may contribute to cancer risk in tissues exposed to combustion products,” Cuomo said in a UC San Diego news release.

More information

There’s more on oral cancers at the American Cancer Society.

SOURCE: University of California San Diego, news release, July 29, 2025