Smoking marijuana significantly increases the risk of head and neck cancers, according to a study in the Cancer Epidemiology, Biomarkers and Prevention. Researchers found that smoking marijuana was almost as damaging as tobacco in terms of respiratory tract cancer, even though the drug was generally regarded as safer.

The study compared the use of marijuana, tobacco and alcohol by 173 patients suffering from head or neck cancers to the habits of a control group of 176 cancer-free patients.

• The study found marijuana users faced 2.5 times the risk of cancer as nonusers.

• Tobacco users faced an increased the risk 3.5 times.

• And people who smoked both tobacco and marijuana raised their risk 36 times.

The lead researcher, Zuo-Feng Zhang, of the Jonsson Cancer Center at the University of California at Los Angeles, predicts more cases of head and neck cancers as baby boomers age.

Source: John O'Neil, "A Downer for Aging Marijuana Users," Vital Signs, New York Times, December 28, 1999.