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CNN
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Using marijuana daily for years could increase the overall risk of head and neck cancer by three to five times, according to a new study that analyzed millions of medical records.
“Our research shows that people who use cannabis, particularly those with cannabis use disorder, are significantly more likely to develop head and neck cancer than those who do not use cannabis,” said the study’s lead author, Dr. Niels Kokot, professor of clinical otolaryngology and head and neck surgery at the Keck School of Medicine at the University of Southern California in Los Angeles.
According to the U.S. Centers for Disease Control and Prevention, cannabis use disorder is diagnosed when a person experiences two or more symptoms such as craving for weed, tolerance to its effects, using more than the intended dose, using marijuana even though it causes problems in life, using in high-risk situations, craving, and inability to quit.
“Although our study did not distinguish between different methods of cannabis consumption, cannabis is most commonly consumed through smoking,” Kokot said in an email. “The link we found likely primarily involves smoking cannabis.”
According to the National Cancer Institute, about 69 percent of people with mouth or throat cancer will survive five years or more after diagnosis. However, if the cancer metabolizes, that rate drops to 14 percent. About 61 percent of people with laryngeal cancer will be alive five years later, a rate that drops to 16 percent if the cancer spreads.
The study used insurance data to examine the association between cannabis use disorder and 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.
“The researchers used a huge data set, which is really extraordinary, and there’s enormous power in looking at such large numbers when we typically only see small studies,” said Califano, who is also director of the Hanna and Mark Gleiberman Head and Neck Cancer Center at UC San Diego.
“On average, people with cannabis use disorder smoke about one joint today and do so for at least two years, if not longer,” said Califano, co-author of an editorial published Thursday in JAMA Otolaryngology–Head & Neck Surgery in conjunction with the new study.
However, he added, the study does not find a link between “occasional recreational marijuana use and head and neck cancer.”
Causes of head and neck cancers
In the United States, head and neck cancers account for 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..
According to experts, smoking, which includes cigarettes, cigars, pipes and smokeless tobacco, and alcohol consumption are the two most common causes of head and neck cancer. Other risk factors include poor oral hygiene, gastroesophageal reflux disease (GERD), weakened immune system, and a diet low in fruits and vegetables. Occupational risk factors include exposure to asbestos and wood dust.
An increasing number of head and neck cancers are caused by 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 malignancy.
Epstein-Barr virus is associated with infectious mononucleosis, also known as the “kissing disease,” as well as various cancers. Researchers estimate that 90% of the world’s population is infected with Epstein-Barr virus. There is a vaccine for human papillomavirus (HPV), which is associated with an increased risk of developing cervical cancer and some non-Hodgkin’s lymphomas.
It is possible to be infected with both viruses at the same time, and this combination is responsible for 38% of all virus-associated cancers, according to research.
The study, published Thursday in JAMA Otolaryngology–Head & Neck Surgery,AThe team analyzed a database of 4 million electronic medical records and found more than 116,000 diagnoses of cannabis use disorder in people with head and neck cancers. These men and women, whose average age was 46, were then matched with people who also had head and neck cancers but had not been diagnosed with cannabis use disorder.
TThe analysis showed that people with cannabis use disorder were about 2.5 times more likely to develop oral cancer; nearly five times more likely to develop oropharyngeal cancer, which is cancer of the soft palate, tonsils and back of the throat; and more than eight times more likely to develop laryngeal cancer. These findings applied to all age groups, the study said.
According to experts, tobacco smoke is one of the main reasons for the link between cannabis use and head and neck cancers. Smoking tobacco doubles the risk of developing squamous cell carcinoma of the head and neck, which accounts for 90% of all head and neck cancers. Heavier tobacco use carries an even higher risk, and when alcohol is added, the risk is even greater.
Because of the way marijuana is smoked (unfiltered, inhaled deeply and held in the lungs and throat for a few seconds), the risk from cannabis smoke may be even greater, experts say.
Another key to the puzzle of how cannabis causes cancer: Research has linked various cannabinoids to tumor growth. According to the National Center for Complementary and Integrative Health, the cannabis plant contains more than 100 cannabinoids, biological compounds that bind to cannabinoid receptors in the human body. In total, each marijuana plant contains about 540 chemicals.
Tetrahydrocannabinol, or THC, is the substance that makes you feel high, while cannabidiol, or CBD, has been shown to have medicinal uses for seizures and epileptic seizures in children.
“Some of the research we’ve already published shows that THC or related compounds can certainly accelerate tumor growth,” Califano said. “We also have data showing that cannabinoids promote the growth of HPV-related throat cancers.”“
With marijuana use on the rise, there is concern that head and neck cancer diagnoses will increase in the coming years, Kokot said.
“As (marijuana) becomes more legalized and socially accepted, we could see a corresponding increase in head and neck cancer cases if the association is confirmed,” he said.
“This highlights the importance of educating people about the potential risks and conducting further research to understand the long-term impacts of cannabis use on the development of cancer.”
Correction: Correction: A previous version of this article confused percentage and risk ratio.
