Study: Cannabis Smoking Not Associated With Increased Lung Cancer Risk Or Other Serious Pulmonary Complications

A forthcoming review to be published in journal Annals of the American Thoracic Society reiterates that the ingestion of cannabis smoke poses nominal pulmonary risks compared to those associated with tobacco smoke. The author of the paper, Donald P. Tashkin, MD, emeritus professor of medicine and medical director of the Pulmonary Function Laboratory at the David Geffen School of Medicine at University of California, Los Angeles performed US-government sponsored studies of marijuana and lung function for over 30 years.

A preview of Dr. Tashkin’s forthcoming review appears on the American Thoracic Society news website here. It reads:

Dr. Tashkin found that regular smoking of marijuana by itself causes visible and microscopic injury to the large airways that is consistently associated with an increased likelihood of symptoms of chronic bronchitis that subside after cessation of use. He also found that the evidence does not indicate that habitual use of marijuana leads to significant abnormalities in lung function when assessed either cross-sectionally or longitudinally, except for possible increases in lung volumes and modest increases in airway resistance of unclear clinical significance.

The author finds no clear link between marijuana use and the development of COPD or lower respiratory tract infections. In addition, “findings from a limited number of well-designed epidemiological studies do not suggest an increased risk for the development of either lung or upper airway cancer from light or moderate use, although evidence is mixed concerning possible carcinogenic risks of heavy, long-term use,” Dr. Tashkin notes. “In summary, the accumulated weight of evidence implies far lower risks for pulmonary complications of even regular heavy use of marijuana compared to the grave pulmonary consequences of tobacco.”

The full paper will be available later this month.

In May, presenters at the annual meeting of the American Academy for Cancer Research reported that subjects who regularly inhale cannabis smoke possess no greater risk of lung cancer than do those who consume it occasionally or not at all — according to an analysis of six case-control studies, conducted between 1999 and 2012, involving over 5,000 subjects (2,159 cases and 2,985 controls) from around the world.

Last year, clinical data published in the Journal of the American Medical Association (JAMA) reported that subjects’ exposure to moderate levels of cannabis smoke, even over the long-term, is not associated with significant adverse effects on pulmonary function.

Vaporizers, which heat marijuana to a point where cannabinoid vapors form, but below the point of combustion, reduce subjects’ intake of potentially hazardous combustible compounds. In several clinical trials, investigators have concluded that vaporization is a “safe and effective” cannabinoid delivery mode that “does not result in exposure to combustion gases.” Researchers also report that vaporization results in higher plasma concentrations of THC compared to smoked cannabis.

8 thoughts

  1. I’m sure your group has addressed this in a fragmented way, but point by point is the stance against legalization outlined by the Obama administration here still factually supported, or are studies like this one refuting it?

    They use a lot of projections which I guess could be plausible, but also could go the other way. Example: They say legalization wouldn’t undercut criminal activity since illegal pot would just be sold at lower, unregulated/untaxed prices. But people could also grow it themselves (analogy home brewing). Conversely, would people really risk potential prosecution for and risk poor quality buying illicit pot after legalization? I mean how many people buy illegal liquor (i.e. moonshine) even though it’s cheaper?

    [Editor’s note: Unfortunately, the federal government, be it the executive branch or anti-drug bureaucracies (i.e., DEA, ONDCP, NIDA, PDFA, DARE, etc…) still largely broadcast propaganda about cannabis.

    This white paper from the Obama Administration is very similar to other templates going back to the Clinton years.

    Those interested with this kind of point-by-point type engagement of government can see an example of such here.

    You’re quite correctly ask the question in conclusion, ‘who buys illegal alcohol?’ when the product is legal and taxed. Other than a small regional area of the country with an affinity for producing an unregulated and taxed alcohol product (ie, moonshine), and even in those regions they hardly scratch the legal market’s reach and efficiencies, there is a teeny and hard to identify market for illegal alcohol products.

    In 5-20 years, after cannabis is legal in a state like CA could a traditional cannabis cultivation region of the country like the ’emerald triangle’ still be a hotbed for anti-govt/anti-regulation of their cannabis crop? Sure.

    Is this a reason the ban cannabis nationwide?


    Will people grow their own cannabis? Sure.

    Will the percentage look similar to the home brew market?

    Yes. Meaning that if the prohibitionist’s argument is to be taken seriously at all, how does the ever-expanding 6,500 commercial brewer industry survive when beer consumers have the legal choice to brew their own?


    Cops and other anti-cannabis groups putting forward this argument increasingly sound ridiculous trying to advance the illogical notion that by legalizing cannabis an underground market will be created. If this is their concern, what do they say to the last 75-year underground (and thriving!) market created by the current prohibition laws??]

  2. The government has known this for quite some time. Big tobacco had a hand in suppressing information like this. Wouldn’t wan’t people having a safer alternative. Who are we to decide that a plant is somehow dangerous? All plants should be investigated for their medicinal useses. It has been on this Earth far longer than we have!

  3. With this whole craze of concentrates i wonder if more concentrated substances have varying effects on the risk? or possibly could one type of rolling paper or papers in general be responsible for increased cancer risks? Regardless i must agree that vaporizers to me at least provide the smoothest most pure experience. And i would assume it to put you “less at risk”.

    Vaporize Me

  4. I think we’ve known this for years now. Anyone who try’s to make it seem like marijuana is as harmful as tobacco has a definite agenda.

  5. Cannabis is more harmful than tobacco because of the federal response to its cultivation, not its personal cosumption. If someone is researching cannabis for its addictive properties, it is because that avenue is the only way to obtain research funds.

  6. With this study taken into account, it now seems ridiculous for life insurance companies to treat medical and recreational users the same as cigarette smokers when it comes to their rates.

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