Jan. 21, 2000 (Lake Worth, Fla.) -- People who smoked pot in the '60s may have something to worry about, if the researchers at the UCLA School of Public Health are correct. They find that head and neck cancer, which often takes 30-40 years to develop, may be related to smoking marijuana. Thus, those who smoked pot in their teens and 20s may just now be feeling its adverse effects.
Published in the December issue of Cancer Epidemiology, Biomarkers & Prevention, this is the first statistical study to look at the relationship between marijuana smoking and head and neck cancer -- including cancers of the tongue, throat, mouth, and voicebox.
The investigators compared a group of 173 patients who had cancer of the head and neck with 176 blood donors without cancer. They asked the subjects questions concerning age, lifestyle, alcohol intake, cigarette smoking, and marijuana use. Adjusting for the effects of alcohol and cigarette use, they found a relationship between the frequency of marijuana use and the disease.
In other words, the number of marijuana cigarettes smoked and the number of years smoked has a direct relationship on the development of these cancers.
Pot smokers were 2.6 times more at risk for head and neck cancer than their non-pot-smoking counterparts. "If they used more than one [marijuana cigarette] a day, the risk jumped to 4.9 times more than someone who never smoked," lead author Zuo-Feng Zhang, MD, PhD, tells WebMD. Zhang is director of the Cancer Epidemiology Training Program and professor of epidemiology at the UCLA School of Public Health.
"I think it makes a lot of sense, because we've known for a long time there's a lot more tar in marijuana -- more than cigarette smoke. So people are being exposed to more carcinogens," Patricia Reggio, PhD, tells WebMD. Reggio, who has researched marijuana (cannabinoids) for more than 15 years, reviewed the study for WebMD. She is a member and past president of the International Cannabinoid Research Association.
A genetic defect may put people at even greater risk, Zhang says. The patients were tested for a genetic defect that predisposes to cancer. Those with the defect who smoked marijuana had a 77-fold higher risk for cancer than those without the defect.
The study also showed that smoking cigarettes increased a person's risk of head and neck cancer. Additionally, alcohol was found to be a risk factor, but it was not as strong as either the genetic risk or cigarette smoking.
However, since the study involved a relatively small number of people, the researchers may not have had enough information on alcohol. David Arnold, MD, from the University of Miami's Sylvester School of Medicine, tells WebMD that he and his colleagues have found a significant risk of cancer development if alcohol is also used with marijuana smoking. "Nobody knows why that is. People talk about the alcohol making the cells more [receptive] to the [cancer-causing agent in marijuana] so that it can actually get into the genetic level," he explains. Arnold is a professor of otolaryngology, in the division of head and neck surgery at the University of Miami, Sylvester Comprehensive Cancer Center.
All in all, Zhang, Arnold, and Reggio agree that this is sobering news for people who smoked pot in the past and those who are smoking it now. They should be forthcoming with their doctors about their recreational drug use. "If they have ever used marijuana, they should see their dentists twice a year to be checked for precancerous lesions," Zhang says. "The message is: Anything you smoke is bad."
- A new study has linked past marijuana smoking with an increased risk of cancers of the head and neck.
- More tar is found in marijuana than in cigarettes, so marijuana smokers have more exposure to cancer-causing agents.
- For those who have ever smoked marijuana, a dental visit twice a year can catch precancerous lesions.