In a study, researchers have found that long-term pot smokers were roughly 62 percent less likely to develop head and neck cancers than people who did not smoke pot. The new study featured 434 patients with head and neck cancers, which include tumors in the mouth, tongue, nose, sinuses, throat and lymph nodes in the neck, and 547 individuals without these cancers seen in the Greater Boston area from December 1999 to December 2003. After factoring out the impact of smoking, drinking, and other factors that might influence the results, smoking marijuana from once every two weeks to three times every two weeks, on average, was associated with about half the risk of head and neck cancer, compared with less frequent use. Those who took up pot smoking at an older age appeared to have less risk of these cancers than those who started it at a younger age. Compared to people who never smoked pot, those who began smoking marijuana between the ages of 15 and 19 years were 47 percent less likely to develop head and neck cancer, while users who began at age 20 or older had a 61 percent reduced risk, Kelsey and colleagues found. The authors note that chemicals in pot called cannabinoids have been shown to have potential antitumor effects. Other studies have linked marijuana use to a reduced risk of some cancers, such as cancer of the prostate, and now head and neck cancer. It's also been suggested that smoking pot may help stave off Alzheimer's disease and help combat weight loss associated with AIDS, and nausea and vomiting associated with chemotherapy in cancer patients.