Studies suggest heavy marijuana smoking could raise cancer risk, but researchers are still working to understand the long-term effects and the role of dosage.
As marijuana becomes legal in more states, many people are asking whether it is actually safe. While the link between tobacco smoking and lung cancer is well established, the connection between marijuana use and cancer remains less clear, according to Brooks Udelsman, MD, a thoracic surgeon with USC Surgery, part of Keck Medicine of USC.
Researchers are continuing to investigate whether marijuana smoking raises the risk of lung cancer. A recent Keck Medicine study led by Niels Kokot, MD, an otolaryngologist with the USC Caruso Department of Otolaryngology – Head and Neck Surgery, found that heavy marijuana smokers may face a greater risk of both small cell and non-small cell lung cancer.
Another study led by Dr. Kokot found that people who use marijuana daily are 3.5 to 5 times more likely to develop head and neck cancers compared to nonusers. These cancers include those affecting the mouth, pharynx, larynx, oropharynx (tongue and tonsils and back wall of the throat), and nearby salivary glands.
Heavy Marijuana Use and Lung Cancer Concerns
As studies continue, Dr. Udelsman says one major unanswered question is how much marijuana use increases cancer risk.
“What we don’t know right now is the dose relationship,” he says. “So, if someone smokes marijuana occasionally once a week, once a month, or a few times a year, do they still have that same risk? My suspicion is that there is probably minimal risk. All we know right now is that people who smoke a lot of marijuana—to the point that they develop a dependency on it or require hospital care or evaluation for it—do appear to have a higher cancer risk.”
Researchers are also examining whether marijuana use could be linked to other cancers, including bladder and gastrointestinal cancers, Dr. Udelsman says.
“With tobacco, we do see an increased prevalence of bladder cancer. Whether that relationship is also the same for heavy marijuana smoking, we don’t know,” he says. “That’s why we’re trying to determine what the risks are so that people can know what risks they’re taking,” he says.
