Cannabis use linked to head and neck cancer risk

Using cannabis heavily and regularly may raise the risk of head and neck cancers, a new study finds.

The research looked at 20 years' worth of medical records from more than 116,000 U.S. adults with cannabis use disorder (CUD). Estimated to affect 3 in 10 cannabis users, the disorder is defined as problematic cannabis use that leads to significant impairment or distress and involves signs of tolerance — in which someone needs to use more of a drug to get the same high — and dependence, including withdrawal symptoms.

Compared to adults without CUD, these individuals were 3.5 to five times more likely to develop head and neck cancers, according to the new study, published Thursday (Aug. 8) in the journal JAMA Otolaryngology-Head & Neck Surgery. These include cancers of the mouth, throat, voice box, saliva glands and oropharynx, which encompasses the tongue, tonsils and back wall of the throat.

"This is one of the first studies — and the largest that we know of to date — to associate head and neck cancer with cannabis use," senior study author Dr. Niels Kokot, a head and neck surgeon at the University of Southern California Head and Neck Center, said in a statement. "The detection of this risk factor is important because head and neck cancer may be preventable once people know which behaviors increase their risk."

Related: Could cannabis treat cancer someday? Here's what the science says so far

The research pulled data collected between 2004 and 2024 from TriNetX, a trove of patient data from 64 U.S. health centers. In addition to the patients with CUD, the study included data from over 3.9 million people without a diagnosis of the disorder.

The people with CUD were directly compared with people of the same age and sex, and the researchers also accounted for alcohol and tobacco use, which are major drivers of head and neck cancers.

Compared with the control group, people with CUD were more likely to develop every type of head and neck cancer, except hypopharyngeal cancer, which affects the lower throat.

The study did not investigate how patients used cannabis — for instance, whether they smoked or took edibles. Thus, it can't say for sure whether it's the smoke that's driving the cancer, given that cannabis smoke contains some carcinogens that are similar to those in tobacco smoke. Alternatively, it could be that active components in cannabis, such as THC, activate certain enzymes that can fuel cancer.

"The cannabinoids themselves could be carcinogenic, and it could also be that the smoke itself has potential for carcinogenesis," Kokot told NBC News.

The study does have some limitations, however. For example, people's cannabis use was self-reported, and the exact doses they were exposed to are unknown.

While it's too soon to say if the link between heavy cannabis use and head and neck cancers holds up over time, "the implications of the report … are sobering," doctors from the UC San Diego Moores Cancer Center and Xiangya Hospital in China wrote in a commentary about the study.

It's worth noting that the study's data spanned two decades in which cannabis use became more commonplace, they wrote. If cannabis can be confirmed to fuel cancer in some way, we might expect that the rate of head and neck cancers linked to the drug will become more common in line with cannabis use, they concluded.

This article is for informational purposes only and is not meant to offer medical advice.

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