SAN DIEGO, May 24 Smoking marijuana does not appear to increase the risk of lung cancer or head-and-neck malignancies, even among heavy users, researchers reported here.
"We expected that we would find that a history of heavy marijuana use, more than 500 to 1,000 uses, would increase the risk of cancer from several years to decades after exposure to marijuana, said Donald Tashkin, M.D., of the University of California in Los Angeles.
But in fact, they reported at the American Thoracic Society meeting here, marijuana use was associated with cancer risk ratios below 1.0, indicating that a history of pot smoking had no effect on the risk for respiratory cancers.
