A recent study has found that consistent daily marijuana smoking over several years may increase the risk of head and neck cancers by 3.5% to 5%. CNN reports that this research, which analyzed millions of medical records, highlights the potential health risks associated with cannabis use.
According to the National Cancer Institute, about 69% of people diagnosed with oral or throat cancer survive for at least five years. However, survival rates drop significantly to 14% if the cancer metastasizes. Tobacco use—including cigarettes, cigars, pipes, and smokeless tobacco—along with alcohol consumption, remains the leading cause of head and neck cancers. Other factors include poor oral hygiene, gastroesophageal reflux disease, a weakened immune system, and a diet low in fruits and vegetables. Occupational exposures to hazards like asbestos and wood dust also contribute.
Dr. Niels Kokot, the study’s senior author and a professor of clinical otolaryngology-head and neck surgery at the Keck School of Medicine at the University of Southern California, stated, “Our research shows that individuals with cannabis use disorder are significantly more likely to develop head and neck cancers compared to non-users.”
Cannabis use disorder is diagnosed when a person exhibits symptoms such as craving marijuana, developing tolerance, using more than intended, and continuing use despite negative life impacts. The US Centers for Disease Control and Prevention outline these criteria.
For laryngeal cancer, the five-year survival rate is 61%, which drops to 16% if the cancer spreads. Dr. Kokot emphasized that while the study did not differentiate between methods of cannabis consumption, smoking is the most common method, and the findings likely relate mainly to smoked cannabis.
The study, which used insurance data, examined the link between cannabis use disorder and head and neck cancers. Dr. Joseph Califano, who was not involved in the study but is the Iris and Matthew Strauss Chancellor’s Endowed Chair in Head and Neck Surgery at UC San Diego, praised the research for its large dataset and significant findings. He noted that the study does not link occasional recreational marijuana use with head and neck cancer.
Experts suggest that smoking marijuana, like tobacco, may increase the risk of head and neck cancers. In the U.S., these cancers account for 4% of all cancer cases, with more than 71,000 new cases and over 16,000 deaths expected in 2024.
Infections with human papillomavirus (HPV) and Epstein-Barr virus (EBV) are increasingly linked to head and neck cancers. HPV is linked to cervical cancer and some non-Hodgkin lymphomas, while EBV is associated with infectious mononucleosis and various cancers. It is estimated that 90% of people are infected with EBV.
The study, published in *JAMA Otolaryngology–Head & Neck Surgery*, reviewed a database of 4 million electronic health records and identified over 116,000 diagnoses of cannabis use disorder among individuals with head and neck cancers. These patients, with an average age of 46, were compared with those who had head and neck cancers but no cannabis use disorder.
The analysis found that individuals with cannabis use disorder were about 2.5 times more likely to develop oral cancer, nearly five times more likely to develop oropharyngeal cancer, and more than eight times more likely to develop laryngeal cancer. This association was consistent across all age groups.
Experts attribute the increased cancer risk to smoke inhalation, noting that smoking tobacco doubles the risk of head and neck squamous cell carcinoma. The risk increases with more frequent tobacco use and alcohol consumption. Given the typical unfiltered, deeply inhaled nature of marijuana smoke, the risk from cannabis smoke could be even higher.
Cannabinoids, compounds found in cannabis, may also play a role in tumor growth. THC, the compound responsible for marijuana’s euphoric effects, and CBD, known for its medicinal benefits, are among the over 100 cannabinoids in cannabis.
Dr. Califano noted that some research indicates THC or THC-like compounds may accelerate tumor growth and possibly enhance the growth of HPV-related throat cancers. As marijuana use rises, there is concern that head and neck cancer diagnoses might increase. Dr. Kokot warned that as cannabis becomes more legalized and socially accepted, there may be a rise in head and neck cancer cases, emphasizing the need for public awareness and further research.
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