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.