Pot's low cancer risk a surprise finding

People who smoke marijuana may be at less risk of developing lung cancer than tobacco smokers, according to a new study.

The study of 2,200 people in Los Angeles found that even heavy marijuana smokers were no more likely to develop lung, head or neck cancer than non-users, in contrast with tobacco users, whose risk increases the more they smoke.

The findings are a surprise because marijuana smoke has some of the same cancer-causing substances as tobacco smoke, often in higher concentrations, said the senior researcher, Donald Tashkin, a professor at the David Geffen School of Medicine at the University of California-Los Angeles.

One possible explanation is that THC, a key ingredient in marijuana not present in tobacco, may inhibit tumor growth, he said in an interview.

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