Study Finds No Cancer-Marijuana Connection

  1. Universal Expat
    Study Finds No Cancer-Marijuana Connection
    By Marc Kaufman
    Washington Post Staff Writer
    Friday, May 26, 2006; A03

    The largest study of its kind has unexpectedly concluded that smoking marijuana, even regularly and heavily, does not lead to lung cancer.

    The new findings "were against our expectations," said Donald Tashkin of the University of California at Los Angeles, a pulmonologist who has studied marijuana for 30 years.

    "We hypothesized that there would be a positive association between marijuana use and lung cancer, and that the association would be more positive with heavier use," he said. "What we found instead was no association at all, and even a suggestion of some protective effect."

    Federal health and drug enforcement officials have widely used Tashkin's previous work on marijuana to make the case that the drug is dangerous. Tashkin said that while he still believes marijuana is potentially harmful, its cancer-causing effects appear to be of less concern than previously thought.

    Earlier work established that marijuana does contain cancer-causing chemicals as potentially harmful as those in tobacco, he said. However, marijuana also contains the chemical THC, which he said may kill aging cells and keep them from becoming cancerous.

    Tashkin's study, funded by the National Institutes of Health's National Institute on Drug Abuse, involved 1,200 people in Los Angeles who had lung, neck or head cancer and an additional 1,040 people without cancer matched by age, sex and neighborhood.

    They were all asked about their lifetime use of marijuana, tobacco and alcohol. The heaviest marijuana smokers had lighted up more than 22,000 times, while moderately heavy usage was defined as smoking 11,000 to 22,000 marijuana cigarettes. Tashkin found that even the very heavy marijuana smokers showed no increased incidence of the three cancers studied.

    "This is the largest case-control study ever done, and everyone had to fill out a very extensive questionnaire about marijuana use," he said. "Bias can creep into any research, but we controlled for as many confounding factors as we could, and so I believe these results have real meaning."

    Tashkin's group at the David Geffen School of Medicine at UCLA had hypothesized that marijuana would raise the risk of cancer on the basis of earlier small human studies, lab studies of animals, and the fact that marijuana users inhale more deeply and generally hold smoke in their lungs longer than tobacco smokers -- exposing them to the dangerous chemicals for a longer time. In addition, Tashkin said, previous studies found that marijuana tar has 50 percent higher concentrations of chemicals linked to cancer than tobacco cigarette tar.

    While no association between marijuana smoking and cancer was found, the study findings, presented to the American Thoracic Society International Conference this week, did find a 20-fold increase in lung cancer among people who smoked two or more packs of cigarettes a day.

    The study was limited to people younger than 60 because those older than that were generally not exposed to marijuana in their youth, when it is most often tried.

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  1. Heretic.Ape.
    Great news! Now if I can just convince my labrat to quit smoking cigarettes...

    But this is wonderful in deflating even more the already rapidly deflating claims of marijuana's dangers. Good find.
  2. Nature Boy
    Finally, a proper study that backs up what I have believed for a very long time. Those idiots with their "one joint equals six cigarettes" can go shove this up their backsides. It's been obvious to me that smoking cannabis isn't as harmful as smoking tobacco. Tobacco causes the lungs to retract, cannabis seems to do the opposite, even with a little tobacco mixed in with it. It's little wonder SWIM's lungs heave anytime he smokes a cigarette and nothing happens anytime he smokes a spliff (granted there's no grit in there).
  3. Nagognog2
    Better make a copy and file it. Something tells me this will be last we see of this study. Then next week: Marijuana proven to cause cancer of the butthole!
  4. augentier
    Interesting says Tashkin still believes that mj is potentially harmful..I'm wondering in which ways he still believes it is harmful..for the mind ? Body? Both?
  5. Nature Boy
    Meh, "potentially harmful" is a nice politically correct catch 22 term for "I don't want to look like a pro-drug advocate". I wouldn't read too much into it. If he had any real doubts, he would announce them for sure. People would probably pay him more to make negative findings more than likely.
  6. darawk
    All I can say is: fucking owned.
  7. The Doors
    I have bookmarked the link to the article!
  8. Alicia
    splendid news. kinda of a whiffy middle finger to the idiots who say otherwise..
  9. Nacumen
    "Friday, May 26, 2006"

    Not really news anymore, is it?
  10. Alicia
    still useful for information gathering references.
  11. Heretic.Ape.
    I didn't see the cited research in the archive. Has anyone grabbed this yet?
  12. grandbaby
    Whoa, nice noticing! Hard to believe this went without comment here and elsewhere when originally posted. The real news is how suppressed it was!

    Nice tidbit to drop into conversation, though, still. And unless further studies refute it, I'll take this as the final word on the subject.
  13. Bajeda
    Ooooohhh, and I bet they definitely are NOT happy!

    Anyone know if this particular study was officially published yet? Swim may have to a take a look around for it and see if he can get it into the archive.

    Hey, its the scientific way. Hard to argue with that one without demonstrating some bias. :p
  14. Heretic.Ape.
    I checked it out. The study is out but I couldn't find a free version (full). It seems my journal privilages don't extend to that particular journal :(
    I might have better luck from the university though so I'll try when I'm there next.
  15. Bajeda
    Whats the exact name of the study? I may be able to procure it.
  16. Heretic.Ape.
    I believe it is this study:
    Marijuana use and the risk of lung and upper aerodigestive tract cancers: results of a population-based case-control study.
    [SIZE=-1]Cancer Epidemiol Biomarkers Prev. 2006 Oct;15(10):1829-34.

    One of the researchers (Tashkin) was quoted in the cited article.
  17. Bajeda
    Marijuana Use and the Risk of Lung and Upper Aerodigestive Tract Cancers: Results of a Population-Based Case-Control Study

    Description: Despite several lines of evidence suggesting the biological plausibility of marijuana being carcinogenic, epidemiologic findings are inconsistent. We conducted a population-based case-control study of the association between marijuana use and the risk of lung and upper aerodigestive tract cancers in Los Angeles.

    Although using marijuana for [​IMG]30 joint-years was positively associated in the crude analyses with each cancer type (except pharyngeal cancer), no positive associations were observed when adjusting for several confounders including cigarette smoking.
  18. chillinwill
    Marijuana Does Not Raise Lung Cancer Risk

    May 23, 2006

    People who smoke marijuana do not appear to be at increased risk for developing lung cancer, new research suggests.

    While a clear increase in cancer risk was seen among cigarette smokers in the study, no such association was seen for regular cannabis users.

    Even very heavy, long-term marijuana users who had smoked more than 22,000 joints over a lifetime seemed to have no greater risk than infrequent marijuana users or nonusers.

    The findings surprised the study’s researchers, who expected to see an increase in cancer among people who smoked marijuana regularly in their youth.

    “We know that there are as many or more carcinogens and co-carcinogens in marijuana smoke as in cigarettes,” researcher Donald Tashkin, MD, of UCLA’s David Geffen School of Medicine tells WebMD. “But we did not find any evidence for an increase in cancer risk for even heavy marijuana smoking.” Carcinogens are substances that cause cancer.

    Tashkin presented the findings today at The American Thoracic Society’s 102nd International Conference, held in San Diego.

    Boomers Reaching Cancer Age

    The study population was limited to people who were younger than 60 because people older than that would probably not have used marijuana in their teens and early adult years.

    “People who may have smoked marijuana in their youth are just now getting to the age when cancers are being seen,” Tashkin says.

    A total of 611 lung cancer patients living in Los Angeles County, and 601 patients with other cancers of the head and neck were compared with 1,040 people without cancer matched for age, sex, and the neighborhood they lived in.

    All the participants were asked about lifetime use of marijuana, tobacco, and alcohol, as well as other drugs, their diets, occupation, family history of lung cancer, and socioeconomic status.

    The heaviest marijuana users in the study had smoked more than 22,000 joints, while moderately heavy smokers had smoked between 11,000 and 22,000 joints.

    While two-pack-a-day or more cigarette smokers were found to have a 20-fold increase in lung cancer risk, no elevation in risk was seen for even the very heaviest marijuana smokers.

    The more tobacco a person smoked, the greater their risk of developing lung cancer and other cancers of the head and neck. But people who smoked more marijuana were not at increased risk compared with people who smoked less and people who didn’t smoke at all.

    The THC Connection

    Studies suggest that marijuana smoke contains 50 percent higher concentrations of chemicals linked to lung cancer than cigarette smoke. Marijuana smokers also tend to inhale deeper than cigarette smokers and hold the inhaled smoke in their lungs longer.

    So why isn’t smoking marijuana as dangerous as smoking cigarettes in terms of cancer risk?

    The answer isn’t clear, but the experts say it might have something to do with tetrahydrocannabinol, or THC, which is a chemical found in marijuana smoke.

    Cellular studies and even some studies in animal models suggest that THC has antitumor properties, either by encouraging the death of genetically damaged cells that can become cancerous or by restricting the development of the blood supply that feeds tumors, Tashkin tells WebMD.

    In a review of the research published last fall, University of Colorado molecular biologist Robert Melamede, PhD, concluded that the THC in cannabis seems to lessen the tumor-promoting properties of marijuana smoke.

    The nicotine in tobacco has been shown to inhibit the destruction of cancer-causing cells, Melamede tells WebMD. THC does not appear to do this and may even do the opposite.

    While there was a suggestion in the newly reported study that smoking marijuana is weakly protective against lung cancer, Tashkin says the very weak association was probably due to chance.

    Cancer risk among cigarette smokers was not influenced by whether or not they also smoked marijuana.

    “We saw no interaction between marijuana and tobacco, and we certainly would not recommend that people smoke marijuana to protect themselves against cancer,” he says.

    By Salynn Boyles, reviewed by Louise Chang, MD
  19. 3rd_high
    Re: Marijuana Does Not Raise Lung Cancer Risk

    I've also read that THC slows or reverses cancer, but the government refuse to fund/research it, despite proven cases.

    I guess they rather stay in the pockets of the trillion dollar pharmaceutical industry. :thumbsdown:
  20. Each Hit
    Re: Marijuana Does Not Raise Lung Cancer Risk

    i remember hearing this back when the results were originally published. any info on any follow-up studies??

    i think the coolest thing about the article is that it's from foxnews. never thought i'd see the day :)
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