Marijuana May Increase Smokers' Risks, Study Says

By chillinwill · Apr 17, 2009 · ·
  1. chillinwill
    Smokers who light up an occasional joint may be putting themselves at a dramatically higher risk of developing chronic lung disease, according to a new study by Canadian researchers.

    The findings indicate that marijuana, even in small doses, seems to accelerate the harmful effects of smoking and greatly boosts respiratory problems and chronic obstructive pulmonary disease ( COPD ). The disease, which is often caused by smoking, actually encompasses a few disorders, including chronic bronchitis and emphysema. People with COPD often have difficulty breathing and shortness of breath, and experience increased coughing. It's one of the leading causes of death in Canada.

    In the study, published today in the Canadian Medical Association Journal, researchers found that, as expected, smokers were at an increased risk of developing COPD. But that risk was much higher among those who smoked cigarettes as well as marijuana, according to Wan Tan of the James Hogg iCapture Centre for Cardiovascular and Pulmonary Research, based at St. Paul's Hospital in Vancouver.

    "Smoking marijuana and cigarettes is harmful for your lungs even in small amounts if you smoke them together," said Dr. Tan, who is the study's lead author.

    But the risk of developing COPD was not heightened among those study participants who said they smoked only marijuana.

    Researchers don't know exactly why smoking tobacco and marijuana apparently boosts the risk of the lung disease so greatly. Dr. Tan said they believe a chemical reaction may occur in the individual's airway that spurs the onset of health problems.

    Study participants who reported smoking both tobacco and marijuana were almost three times more likely to develop COPD than non-smokers, as determined by spirometric testing.

    In the study, researchers surveyed nearly 900 randomly selected Vancouver residents aged 40 or over.

    Researchers defined smokers as anyone who reported having at least 365 cigarettes in their lifetime, while marijuana users were defined as anyone who had smoked the substance in their lives. Researchers defined substantial marijuana use as anyone who reported smoking at least 50 marijuana cigarettes in their life.

    They found the risk of developing COPD among cigarette smokers increased if they were heavy marijuana users.

    While the risk of COPD didn't seem to noticeably

    increase among those who only smoked marijuana, that doesn't mean they're not doing damage to their lungs.

    Dr. Tan said the study found the risk of developing COPD was slightly higher among those who smoked only marijuana. The increase was too small, however, for researchers to draw conclusions about health risks.

    More research should be done focusing solely on the health risks of smoking marijuana, Dr. Tan said, to address public confusion about the issue.

    "It's not really widely known that it has this harmful effect. I think [people] are probably a bit confused by the lack of information in the public domain to tell them that it's actually got a harmful effect."

    Despite this, an editorial being published today with the study suggests that marijuana users may not need to worry their habit will lead to serious lung problems. Dr. Tan's study, as well as past research, hasn't identified a strong association between marijuana use and chronic lung disease, writes Donald Tashkin, medical director of the Pulmonary Function Laboratory in the division of pulmonary and critical care medicine at the David Geffen School of Medicine at the University of California, Los Angeles.

    Dr. Tashkin argued the scant evidence supporting the link means that "we can be close to concluding that marijuana by itself does not lead to COPD."

    Author: Carly Weeks
    Pubdate: Tue, 14 Apr 2009
    Source: Globe and Mail

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  1. Greenport
    "But the risk of developing COPD was not heightened among those study participants who said they smoked only marijuana."

    Looks like swiM's in the clear ;)

    Don't smoke cigarettes guys, they're bad for you. *Takes rip off bong* :)
  2. Nature Boy
    Peculiar finding. Without actually being able to identify this supposed chemical reaction, one might suspect that the damage is caused by the habits of the smokers. Perhaps marijuana-using tobacco smokers inhale regular cigarettes deeper. Although cigarettes are obviously harmful, you rarely see attention given to the actual way people smoke. Some people lightly puff away on a cigarette and stomp it out. Others suck up those cigarettes to the last grain of tobacco. Over time, this difference could be vital.
  3. chillinwill
    Smoking both tobacco and marijuana increases the risk of respiratory symptoms and chronic obstructive pulmonary disease (COPD), found a study in the Canadian Medical Association Journal. Smoking only marijuana, however, was not associated with increased risks.

    The study, which surveyed 878 people aged 40 years or more in Vancouver, Canada, was part of the Burden of Obstructive Lung Disease (BOLD) Initiative that sought to determine the prevalence of COPD in adults over 40 years in the general population. It differed from other studies in that the study population was older and the prevalence of tobacco smoking was lower in participants.

    COPD is characterized by diseased lungs and narrowed airways and is associated with high mortality.

    The researchers defined smokers as people who reported smoking at least 365 cigarettes in their lifetime, and a history of marijuana smoking as self-reporting of any previous smoking.

    While tobacco smoking was associated with increased risk, smokers who reported using both tobacco and marijuana were 2.5 times more likely than nonsmokers to have respiratory symptoms and almost 3 times more likely to have COPD as defined by spirometric testing.

    "We were able to detect a significant synergistic effect between marijuana smoking and tobacco smoking," write Dr. Wan Tan of the University of British Columbia and St. Paul's Hospital and coauthors. "This effect suggests that smoking marijuana (at least in relatively low doses) may act as a primer, or sensitizer, in the airways to amplify the adverse effects of tobacco on respiratory health."

    The researchers were limited by lack of data on the potential variations in marijuana potency, on differences in inhalation and the number of smokers who combine both substances in the same cigarette.

    In a related commentary, Dr. Donald Tashkin of the University of California Los Angeles (UCLA) writes that "the findings of Tan and colleagues add to the limited evidence of an association between marijuana use and COPD because their study focuses on an older population (aged 40 or older) that is at greater risk of COPD." Previous studies have failed to find an additive effect of marijuana and tobacco on either chronic respiratory symptoms or abnormal lung function in younger smokers. Dr. Tashkin states that "we can be close to concluding that marijuana smoking by itself does not lead to COPD."

    However, Dr Wan Tan and coauthors conclude that "Although our study had insufficient power to show an association between marijuana alone and increased risk for COPD, it remains uncertain whether marijuana by itself is harmful for the lungs. Larger studies are needed to address this critically important issue in the future."

    April 18, 2009
    Science Daily
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