Using cannabis, the most commonly consumed illicit substance worldwide, increases risk of head and neck cancer, according to a new study by the University of Southern California (USC) Head and Neck Center, part of Keck Medicine of USC, and the USC Caruso Department of Otolaryngology.
The research team tracked cancer cases in adults with one to five years of cannabis use, without distinguishing between the types of use. They found that adults with cannabis dependence, known as cannabis use disorder, are 3.5–5 times more likely to develop head and neck cancer than those who do not use the substance. The researchers compiled 20 years of data acquired via a health research network of 64 health care organizations that gathered information from more than 90 million individuals.
Notably, the research team found that the prevalence of head and neck cancer among those with cannabis use disorder was independent of other factors like age, gender, and ethnicity. Alcohol and tobacco use, which have also been associated with head and neck cancer, did not play a role in the increased risk associated with cannabis.
The study was published in JAMA Otolaryngology-Head and Neck Surgery. The senior author is Niels C. Kokot, MD, a head and neck surgeon with the USC Head and Neck Center.
“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,” said Kokot. “The detection of this risk factor is important because head and neck cancer may be preventable once people know which behaviors increase their risk.”
Head and neck cancer, the sixth most common cancer in the world, includes several cancers like cancer of the mouth, pharynx, larynx, oropharynx (tongue, tonsils, and the back wall of the throat), and adjacent salivary glands.
The researchers discovered that those with cannabis use disorder had higher rates of all types of head and neck cancers.
Kokot and his colleagues hypothesize that the primary reason why cannabis raises the risk of head and neck cancer is the damaging effect of smoke. Cannabis is primarily consumed through inhalation (although the study did not distinguish between methods of consumption). Additionally, research has shown that tobacco smoke contains numerous chemicals that cause DNA damage and inflammation that, if unchecked, can lead to cancer. The study team speculates that cannabis smoke may cause similar harm.
In fact, Kokot said that there is some evidence that the smoke from cannabis may be worse than tobacco smoke.
“Cannabis smoking is typically unfiltered and involves deeper inhalation compared to tobacco,” he said. “Additionally, cannabis burns at a higher temperature than tobacco, increasing the risk of cancer-causing inflammation.”
Kokot would like to see further research examining the link between cannabis and head and neck cancer. In the meantime, he hopes this study will help people make more informed choices and raise awareness about the link between head and neck cancer and cannabis use.
