Smoking pot reduces cancer risk, study?

NEW YORK (Reuters Health) - You've heard about using marijuana and drugs derived from it to keep some of the side effects of toxic cancer chemotherapy in check. But what if smoking marijuana for 10 to 20 years could actually protect against certain tumours?

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 tumours 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.