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Marijuana Does Not Increase Risk Of Lung Cancer

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Marijuana habit not linked to lung cancer

WASHINGTON – Regular cannabis smokers are no more likely to develop lung cancer than are people who indulge occasionally.

The finding of no significant increased risk held true whether the smokers imbibed once or twice – or more – each day, and regardless of how many years they had smoked, Dr. Li Rita Zhang reported at the annual meeting of the American Association of Cancer Research.


©Scott Harms/iStockphoto.com

According to a recent study, habitual cannabis smokers had no significant increase in cancer risk than those who only smoke once or twice per day.

The study included data from six case-control studies conducted from 1999 to 2012 in the United States, Canada, the United Kingdom, and New Zealand, with a subject pool of 2,159 lung cancer cases and 2,985 controls. All of the studies were part of the International Lung Cancer Consortium (ILCCO), an international group of lung cancer researchers with the aim of sharing comparable data from ongoing and recently completed lung cancer studies from different geographical areas and ethnicities.

Dr. Zhang of the University of California, Los Angeles, performed two analyses. One compared all lung cancer cases and all controls, regardless of concurrent or past tobacco use. Then, to reduce confounding by tobacco, she restricted the analysis to those who had never smoked tobacco. That group comprised 370 cancer cases and 1,358 controls. The models were also adjusted for age, sex, sociodemographic factors, and tobacco pack-years. Habitual use was defined as one joint per day per year.

When compared with cannabis smokers who also used tobacco, habitual pot smokers had no significant increase in cancer risk.

In an analysis of marijuana smokers that excluded tobacco smokers, there were no significant differences in any of the comparisons, including habitual vs. nonhabitual use; number of joints smoked per day; duration of up to 20 years or duration of more than 20 years.

Other literature has shown a link between cannabis smoking and lung cancer, pulmonologist Michael Alberts said in an interview. However, he said, "The conventional wisdom is that cannabis smoking is not as dangerous as cigarette smoking."

The difference in risk is likely related to chemical additives in commercial cigarettes that aren’t present in most methods of inhaling marijuana smoke.

As a general recommendation, smoking anything isn’t good for the respiratory system, said Dr. Alberts, chief medical officer of the Moffitt Cancer Center, Tampa. But for patients using medical marijuana, the benefit could outweigh the risks.

"You can think of it as similar to a CT scan. Radiation isn’t good, but if the scan is something beneficial and the risk is low, you take it. If cannabis is indicated, and if it’s legal, and if there’s literature backing up the indication for use, then you weigh the risk of smoking and the benefit it could bring, and make the decision."

Dr. Zhang declined to comment on the study. In her poster presentation she noted that, "Our results cannot preclude the possibility that cannabis may exhibit an association with lung cancer risk at extremely high dosage over long periods of continued exposure."

Dr. Zhang did not disclosure any financial relationships. Dr. Alberts said he had no disclosures.


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well another study with truthful information that HAD to be funded outside the US


they still won't issue any permit for any study/science without a pre-determined negative outcome


the article doesn't make mention of another property of marijuana that I've always believed was part of the puzzle.


as a natural expectorant, marijuana smoke breaks up mucus and MAKES you cough. deep, productive, lung clearing coughs.


I've always felt that a good bong/skillet rip, one that brings tears to your eyes just before you cough up a quart of irritants, contaminates and mucus from deep within your lungs, removes more than it ever could have deposited.


after all these years, even with my cigarettes, I still have the lung capacity to back this editorial up!! latest test, I was able to blow the ball to the top and even hold it there for a sec, every time. also was able to levitate my ball up to the target mark (about 2/3rd's up) and keep it there for an easy 5 count.

never had a Dr. argue with me that I couldn't have smoked both cigarettes and "that crazy amount" of marijuana EVERY day for over 30

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As has been pointed out, this isn't really news to many of us.  What is important is that it came off a main stream Internal Medicine news serve I am on.  Studies are nice, the fact that they are making inroads into the traditional medical literature and being discussed by non-cannabis docs is the good news. I also put it up to get it a little google love to get the article a little higher in the ratings.  I suggest others post it around as well on some of the other boards.  We want it found.


Dr. Bob

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  • 1 year later...

It would be easy enough to urge a no vote on all three, and to call on the city to impose a full-scale ban instead. It was sloppily written and partly because it set up an inevitable conflict with the federal government, which continues to classify marijuana as illegal and dangerous.

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