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    Smoking Pot, Cigarettes Ups COPD Risk

    Study Shows Higher Risk for the Lung Disease Among Smokers of Both Marijuana and Tobacco

    COPD Risk continued...

    When COPD was clinically confirmed though a diagnostic method known as spirometric testing:

    • The incidence of COPD among participants who smoked cigarettes alone was 2.7 times higher than among nonsmokers.
    • The incidence of COPD was 2.9 times higher among participants with a history of smoking both cigarettes and pot, even after controlling for other risk factors for the pulmonary disease.
    • COPD risk among people who smoked marijuana, but not tobacco, was slightly higher than among nonsmokers, but the increase was not statistically significant.

    The study appears in the April 14 issue of the Canadian Medical Association Journal.

    Marijuana and COPD

    Tan tells WebMD that the fact that no link was found between pot smoking alone and COPD does not mean that marijuana is not harmful to the lungs.

    She says the study was probably too small, with too few participants who identified themselves as marijuana smokers alone, to show an association.

    "We can't say that smoking marijuana alone does not increase the risk for COPD," she says. "We definitely need bigger studies to explore the question."

    Donald P. Tashkin, MD, a researcher on marijuana and pulmonary disease, agrees that firm conclusions cannot be made about the association between marijuana smoking and COPD based on the research that has been done.

    He notes that the studies have been limited by their small size and uncertain accuracy of self-reported marijuana use.

    But in an editorial accompanying the study, Tashkin writes that the research makes an increasingly compelling case that smoking marijuana alone is not a major risk factor for lung disease.

    Tashkin's own research, reported in 2006, found no link between marijuana use and lung cancer.

    "Given the consistently reported absence of an association between use of marijuana and abnormal [lung function] or signs of macroscopic emphysema, we can be close to concluding that smoking marijuana by itself does not lead to COPD," he writes.

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