As marijuana becomes legal in more states, many people assume it is relatively safe. But when it comes to cancer, the picture is far less clear. While tobacco smoking has long been established as a major cause of lung cancer, scientists are still working to understand exactly how marijuana affects cancer risk, according to Brooks Udelsman, MD, a thoracic surgeon with USC Surgery at Keck Medicine of USC.
Researchers continue to investigate whether smoking marijuana increases the likelihood of developing cancer. A recent Keck Medicine study led by Niels Kokot, MD, an otolaryngologist at the USC Caruso Department of Otolaryngology -- Head and Neck Surgery, found that people who smoked large amounts of marijuana appeared to face a higher risk of both small cell lung cancer and non-small cell lung cancer.
In another study, Dr. Kokot and colleagues reported that people who used marijuana daily were 3.5 to 5 times more likely to develop head and neck cancers than nonusers. These cancers include those affecting the mouth, pharynx, larynx, oropharynx (tongue and tonsils and back wall of the throat), and nearby salivary glands.
How much marijuana is too much?
Although the evidence linking heavy marijuana smoking to cancer continues to grow, researchers still do not know exactly how much use is required before the risk begins to rise.
