Cannabis use linked to head and neck cancer risk

According to a new study, heavy and frequent cannabis use may increase the risk of head and neck malignancies.

Twenty years’ worth of medical records from over 116,000 adult U.S. patients with cannabis use disorder (CUD) were examined in this study. The disorder, which is thought to impact three out of ten cannabis users, is characterized by problematic cannabis use that causes noticeable impairment or distress. It also includes symptoms of dependence, such as withdrawal, and tolerance, which is the need to take more of a substance to experience the same high.

The new study was published in the journal JAMA Otolaryngology-Head & Neck Surgery on Thursday, August 8, and found that adults with CUD had a 3.5 to 5 times higher risk of head and neck cancers. These include malignancies of the tongue, tonsils, and back wall of the throat as well as those of the mouth, throat, voice box, saliva glands, and oropharynx.

Senior research author Dr. Niels Kokot, a head and neck surgeon at the University of Southern California Head and Neck Center, stated in a statement that “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.” “The detection of this risk factor is important because head and neck cancer may be preventable once people know which behaviors increase their risk.”

The study used information gathered from TriNetX, a treasure mine of patient records from 64 U.S. health facilities, between 2004 and 2024. Apart from the CUD patients, the study encompassed information from more than 3.9 million individuals who were not diagnosed with the illness.

In addition to taking tobacco and alcohol use into consideration—two key risk factors for head and neck cancers—the researchers also directly compared the individuals with CUD to others of the same age and sex.

With the exception of hypopharyngeal cancer, which affects the lower throat, those with CUD had a higher risk of developing any kind of head and neck cancer when compared to the control group.

The study did not look at the patients’ cannabis use habits, such as smoking or consuming edibles. Because some of the carcinogens in cannabis smoke are comparable to those in tobacco smoke, it is therefore impossible to determine with certainty if the smoke is the cause of the cancer. On the other hand, it’s possible that THC and other active ingredients in cannabis cause specific enzymes to be activated, which can promote cancer.

“The cannabinoids themselves could be carcinogenic, and it could also be that the smoke itself has potential for carcinogenesis,” Kokot stated to NBC News.

Nonetheless, there are several restrictions on the study. For instance, individuals self-reported their cannabis use, hence it’s unclear what dosages they were exposed to.

Doctors from the UC San Diego Moores Cancer Center and Xiangya Hospital in China said in a commentary about the study that “the implications of the report… are sobering,” even if it’s too early to tell if there is a lasting link between high cannabis usage and head and neck malignancies.

They noted that the study’s data covered a two-decade period during which cannabis use increased in popularity. They concluded that if it can be demonstrated that cannabis in some manner causes cancer, we could anticipate an increase in the frequency of head and neck malignancies associated with cannabis usage.