Using marijuana daily for years may raise the overall risk of head and neck cancers by 3.5% to 5%, according to a new study that analyzed millions of medical records.
Research shows that people who use cannabis, particularly those with a cannabis use disorder, are significantly more likely to develop head and neck cancers compared to those who do not use cannabis,” said senior study author Dr. Niels Kokot, a professor of clinical otolaryngology-head and neck surgery at the Keck School of Medicine at the University of Southern California in Los Angeles.
Cannabis use disorder is diagnosed when a person has two or more of such symptoms as craving weed, becoming tolerant to its effects, using more than intended, using marijuana even though it causes problems in life, using it in high-risk situations, experiencing withdrawal and being unable to quit, according to the US Centers for Disease Control and Prevention.
“While our study did not differentiate between methods of cannabis consumption, cannabis is most commonly consumed by smoking,” Kokot said in an email. “The association we found likely pertains mainly to smoked cannabis.”
Some 69% of people with a diagnosis of oral or throat cancer will survive five years or longer after their diagnosis, according to the National Cancer Institute. If the cancer metabolizes, however, that rate drops to 14%. About 61% of people diagnosed with cancer of the larynx will be alive five years later — a rate that drops to 16% if the cancer spreads.
The study used insurance data to look at the association of cannabis use disorder with head and neck cancers, said Dr. Joseph Califano, the Iris and Matthew Strauss Chancellor’s Endowed Chair in Head and Neck Surgery at the University of California, San Diego. He was not involved in the study.
Causes of head and neck cancers
In the United States, head and neck cancers make up 4% of all cancers, with more than 71,000 new cases and more than 16,000 deaths expected in 2024, according to the National Foundation for Cancer Research.
Tobacco use, which includes smoking cigarettes, cigars, pipes and smokeless tobacco, and the use of alcohol are the two most common causes of head and neck cancers, experts say. Other risk factors include poor oral hygiene; gastroesophageal reflux disease, or GERD; a weakened immune system; and a diet low in fruits and vegetables. Occupational risk factors include exposure to asbestos and wood dust.
A growing number of head and neck cancers are due to infection with the human papillomavirus or HPV, or the Epstein-Barr virus, or EBV, which are DNA viruses that affect genes, making them susceptible to malignancies.
Epstein-Barr virus is linked to infectious mononucleosis, also called the “kissing disease,” as well as various cancers. Researchers estimate that 90% of the world’s population is infected with EBV. A vaccine is available for HPV, which is linked to a high risk of developing cervical cancer and some non-Hodgkin lymphomas.
