High cannabis use may inflate the threat of oral cancer, UCSD study suggests

As cannabis, or marijuana, becomes more widely available and socially acceptable than ever before, a recent study by the UC San Diego School of Medicine indicates a close association between frequent cannabis use and long-term health risks.

The study, published online by Preventive Medicine Reports, was authored by Raphael Cuomo, an associate professor in the Department of Anesthesiology and a member of UCSD’s Moores Cancer Center.

Cuomo’s study tracked decades-long records from 45,000 patients in the University of California Health Data Warehouse across six academic medical centers.

Overall, screenings spanned January 2012 to December 2019, and data was collected through December 2024.

According to the study, Cuomo found:

• The likelihood of contracting oral cancer within five years — adjusting for age, sex, body mass index and smoking tendencies — was 325% higher in patients diagnosed with cannabis use disorder, or CUD.

• People diagnosed with CUD who also smoke tobacco were 624% more likely to contract oral cancer within five years than those without CUD.

CUD is a psychological diagnosis that doesn’t require a specific level of consumption, Cuomo said. But smoking at least 14 cannabis cigarettes a week is seen as a benchmark for someone to develop the disorder, he said.

Recent research indicates that about three in 10 cannabis users will develop CUD at some point, though it requires a formal diagnosis and is not a catch-all for semi-frequent users, he said.

“It is certainly possible for somebody that recreationally uses cannabis to consume more than 14 joints per week and not develop cannabis use disorder and have some sort of healthy psychological relationship with cannabis,” Cuomo said. “But typically speaking, those who do have cannabis use disorder have higher consumption of cannabis compared to people who do not have cannabis use disorder.

“The implications of this, of course, is that consuming a high amount of cannabis is going to put you at much higher risk for oral cancer.”

A statement from UC San Diego Health says that while many people consider cannabis a safer alternative to substances such as tobacco and alcohol, the jury is still out on its health effects.

Cuomo said he “was not entirely surprised there was an association” between cannabis use disorder and oral cancer, but “three times the odds is very high, so the magnitude of it was a little surprising.”

Cuomo said he hopes to further assess “long-term oncologic risks” of what he describes as problematic cannabis use.

But he emphasized that his study is not a “pros and cons” list about legalization of marijuana.

“This study is not saying that legalization is good or bad,” Cuomo said. “This study is saying that in clinical care, we have to consider whether or not a patient is frequently exposed to cannabis, and if they are, it’s likely a good idea for them to be screened for oral cancer.

“If we catch oral cancer early, like other cancers, that makes it much more treatable and much less likely that it is going to be disabling for the patients.”

To read Cuomo’s full study, go to sciencedirect.com/science/article/pii/S2211335525002244.

Related story:

Careful treatment timing can improve results against oral cancer, UCSD study says