Study: Habitual Marijuana Smoking Not Associated With Increased Risk Of Lung Cancer

Subjects who regularly inhale cannabis smoke possess no greater risk of contracting lung cancer than do those who consume it occasionally or not at all, according to data published online ahead of print in the International Journal of Cancer.

An international team of investigators from Canada, New Zealand, the United Kingdom, and the United States analyzed data from six case-control studies involving over 5,000 subjects (2,159 cases and 2,985 controls) from around the world.

Authors concluded, “Results from our pooled analyses provide little evidence for an increased risk of lung cancer among habitual or long-term cannabis smokers.”

Investigators had previously presented their data at the 2013 annual meeting of the American Academy for Cancer Research.

Their findings are similar to those of a 2013 review published in the journal Annals of the American Thoracic Society, which concluded: “[H]abitual use of marijuana alone does not appear to lead to significant abnormalities in lung function. … Overall, the risks of pulmonary complications of regular use of marijuana appear to be relatively small and far lower than those of tobacco smoking.”

An accompanying commentary in the same journal affirmed, “[C]annabis smoking does not seem to increase risk of chronic obstructive pulmonary disease (COPD) or airway cancers. In fact, there is even a suggestion that at low doses cannabis may be protective for both conditions.”

Preclinical studies have documented that cannabinoids possess potent anti-cancer properties, including the inhibition of lung cancer cell growth. To date, however, scientists have yet to conduct controlled clinical trials replicating these results in human subjects.

The abstract of the study, “Cannabis smoking and lung cancer risk: Pooled analysis in the International Lung Cancer Consortium,” appears online here.

28 thoughts

  1. Marijuana prohibition is built on scientific fraud. The government discovered that THC killed lung cancer cells in 1974. That was 40 years ago! It is unconscionable that still there are no clinical trials in humans. The entire science community in America deserves to be censured for having turned a blind eye to this nonsense for 40 years.

    [Paul Armentano responds: Correct. The first preclinical models showing cannabinoids possess anti-cancer activity were conducted in 1974 and this data was published in 1975 in the Journal of the National Cancer Institute: Notably, CBD did NOT show anti-cancer activity in these models:

    “Lewis lung adenocarcinoma growth was retarded by the oral administration of delta9-tetrahydrocannabinol (delta9-THC), delta8-tetrahydrocannabinol (delta8-THC), and cannabinol (CBN), but not cannabidiol (CBD). Animals treated for 10 consecutive days with delta9-THC, beginning the day after tumor implantation, demonstrated a dose-dependent action of retarded tumor growth. Mice treated for 20 consecutive days with delta8-THC and CBN had reduced primary tumor size. CBD showed no inhibitory effect on tumor growth at 14, 21, or 28 days. Delta9-THC, delta8-THC, and CBN increased the mean survival time (36% at 100 mg/kg, 25% at 200 mg/kg, and 27% at 50 mg/kg, respectively), whereas CBD did not.”]

  2. Re: Concentrates

    (Legal MMJ user here) A couple months ago I picked up a vaporizer pen that uses cartridges filled with concentrate. The “high” is not too much different overall, maybe more of a body high than the flower. When it comes to hybrids and indicas I really do prefer the vaporizer. With sativas I prefer the flower; the concentrate gives maybe too much of a body high for my tastes (although someone more athletically oriented might love it)

    I think the vape pens should be a positive contributor to our movement. Less combustible material going into your body!

    I see the point about edibles etc. having a possibly negative influence. This can be avoided by starting a sincere movement to get all “stoners” to act with class — no need to glorify it — just enjoy it and live your life.

  3. “The entire science community in America deserves to be censured for having turned a blind eye to this nonsense for 40 years.”

    To thwart the advance of medical science is a crime against us all.

  4. Well this is fantastic news. I had no idea this much research has been done on pot. It’s a travesty that the substance which could help with cigarette addiction and alcohol abuse is the exact substance that the government considers to have no therapeutic use!

    The root of all evil is economics. Economics made pot illegal and through economics is the only way pot will be slowly legalized. Look at the laboratories of democracy in the US, Colorado and Washington, to see that it is the economic argument that has swayed voters. Nothing to do with research. The research is conclusive.

    America, smokers and non, let’s join hands to take the money away from criminal syndicates and build some fucking schools cuz I’m gonna smoke whether it’s legal and healthy or not.

  5. Someone needs to tell Gov Cuomo & Friends about this.
    Our bill in NY they made smoking it illegal, i think it is now a felony too Fuckin sad.

  6. I heard patents last 20 years. Any hope patent “507” for cannabis as neuroprotectants owned by the Department of Health and Human Services could become open source within 7 years since it was unconstitutionally, immorally and hypocritically established in 2001?

  7. And the scientific evidence just keeps pouring in. This is government imposed moral values. This is a violation of the first amandment.

  8. While smoking should of course remain legal on private property, smoking cannabis will quickly become increasingly socially unacceptable. Vaporization of buds is low odor, clean and not a fire or security risk, even when traveling.
    Cannabis buds vaporized or low dose cooked should be promoted as the ideal form of cannabis consumption. This will counter the current tactic the pharmaceutical industry is using in attempt to takeover the cannabis industry. Americans have far more trust in cannabis buds than anything in pharmaceutical or concentrated form.
    Cannabis buds also provides the most support for the legalization of small secured private cannabis gardens. Small gardens avoid all the negative aspects associated with cultivation in residential areas. For a small garden, off the shelf small carbon filters remove all odor, and cool to the touch LED lighting eliminates all fire risk. These products plug into a standard outlet, there is no dangerous alteration to wiring or high voltages, small garden LEDs are very low wattage.
    Legitimate use of concentrates is mainly for serious medical conditions. It would make sense for Norml to propose that there should be minimal regulation of cannabis buds for adults, but concentrates are what need oversight.

  9. @Paul – Cuomo needs to read this. I’ll send him a copy.

    Q: Has anyone heard how the Kentucky hemp crop is doing?

    Once all states realize the potential economic benefits and no risk reward for hemp farming we need to refrain from saying “I told you so” and say let’s strengthen our nation and grow more.

  10. I think there needs to be some kind of organic pot shop campaigns or projects to make sure monsanto doesn’t take over and there should be some kind of symbol to let people know if certain shops are organic so we can continue to see more great studys like this one and keep monsanto out

  11. @Ray
    The Kentucky hemp test plots have been planted within the last few weeks. It will be a couple of years before the testing phase is completed. Then we will know what seeds grow best in the area, along with the best techniques for growing on a farm scale.

  12. I quit smoking nicotine the same way Willie Nelson did when I was almost 18;
    I smoked my first joint.
    There were no vaporizers back then, and it wasn’t like I needed to smoke another joint the way I “had” to smoke another cigarette. I was hanging with a girl that smoked a pack a day. After I smoked 1 rolled marijuana joint I could never smoke another corporately packed tobacco product again because it smelled and tasted awful. Tobacco cigarettes suddenly twisted my stomach. Im 36 years old and never craved another cigarette. Still smells like carbon monoxide death buried under suicidal tendencies. And weed is nice, but unless I was sick, i never felt like I HAD to have some marijuana. Funny thing is I only smoked tobacco When I was sick and thanked God I quit when I did.
    Google Altria and Phillip Morris.
    Then google ” marijuana cures cancer.”

  13. One probably should take remember that just because they didn’t find evidence that cannabis smoke increases cancer or emphysema risk, doesn’t prove that it doesn’t.

    Smoke from a joint is much harsher and contains more tar than a cigarette.

    [Editor’s note: “Smoke from a joint is much harsher and contains more tar than a cigarette.”

    Is this accurate? What scientific papers can you cite that support your claim?]

  14. @ Charles, no marijuana doesn’t have anywhere near the same amount of “tar” as does tobacco. The lying asshats just call CBD and THC and other cannabiniods as “tar”. They say that something good is bad and even though it has been explained to people a thousand times, yet morons still parrot this goofy message that good chemicals are the same as toxic chemicals. You can use hydrogen peroxide to clean your cuts and scrapes, but would you also use bleach for the same purposes?

  15. I can say I am 51 and started smoking weed only at the age of 15. Just had a check up and my lungs are clear as a bell Hmmmm! I must say though I do love edibles and vaping which does cut down on the smoking… Plus you get a better effect! LUV Da WEED!

  16. Hello Charles, I need to breakdown this statement, “One probably should take remember that just because they didn’t find evidence that cannabis smoke increases cancer or emphysema risk, doesn’t prove that it doesn’t.

    Okay, on the surface what you’re saying sounds logical. However, this is not a case where an individual has been accused of a misdeed and this statement then would apply. “Well we don’t have any evidence he robbed the bank, but he could have.” That statement makes sense.

    But they didn’t study one case, they studied 2,159 cases with 2,985 controls which means that if marijuana was causing cancer, well then we’d see an up tick in the number of cancer cases in the marijuana using group just like we see in the tobacco/cigarette using group. Which is how we proved tobacco causes cancer.

    So really, what you said is more like, “Well sure they photographed all the different phases of the moon, but I think maybe the moon stays full all month long anyway. Just a hunch.”

    Uh, what??? It makes me think you didn’t really understand the point of this article… Because next you could include, “And just because they showed tobacco causes cancer, doesn’t mean it doesn’t cause cancer too.” Again, huh???

  17. Pot contains nothing like the tar of cigarettes. It has an entirely different chemical makeup. While the allegation is frequently made by pot prohibitionists, I have seen none of them address its chemical makeup. Putting aside this point, to the extent that joints contain something like tar, it does not cause cancer like cigarette tar. As to it being harsher, in general, I find pot smoke to taste a lot less harsh. Do you have evidence of your claims? Harsh in what way? Also, pot smokers smoke far fewer joints than, e.g. three pack a day smokers.

  18. To be honest with you all at my age, responding to the tar non debate issue is anal. Anybody who has smoked cigs at one time or another and pot knows the truth. Their tar stance is based on old school yellow fingers. Please cigs and pot, the statement speaks for itself. Everybody must just grow all together now!

  19. Gee what a surprise, NOT.
    If cannabis smoking caused cancer, that would have been found years ago, with heavy users of cannabis. Since that is has not happened, besides with people who already smoke many ordinary cigarettes, it’s safe to conclude, that cannabis does not add to the problem.

    Instead, there’s data to conclude that cannabis does the opposite, and can actually prevent, and cure cancer.

    If it caused cancer, we would have found this years ago. We did find, that tobacco causes more then one type of cancer. That is a fact, and the stuff remains legal for any adult to do. (I started when I was 13-years-old. I am 44 now, and have quit going on 3 years.)
    Quit smoking Pot? NO. Our government can lie to me all they want, that cannabis is a bad drug, but as far as I’m concerned, it’s really not. The Buzz goes away in just a few hours, and you can usually do a lot more under its influence then you can when drunk.

    Why on God’s green earth, don’t they try to regulate on a legal level? Prohibition of cannabis makes no sense at all. Pharmaceutical companies? They will eventually lose some of their money, as public opinion changes, and the majority of Americans demand fair laws. They might as well give in, and then move on. They’ll find other ways to make money.

    Times are changing, and eventually, it will be legal nation wide. And eventually after that, throughout the world.

  20. @ Julian:
    I too stopped tobacco using MJ (1970): MJ is an excellent substitute for tobacco; many Herbs can be used; Hemp; Mint; White Willow;
    Marijuana is an excellent way to “be Sober too
    Marijuana not a “drug”; Marijuana is an Herb!@

  21. If I were a tobacco co. researcher: I would conduct tests using different Herbs and patent the world’s first Herbal Cigarette w/Hemp Leaves(CBD or male plants) w Mint buds!
    Give the people what is beneficial for Health!

  22. Anne, they have known for almost 50 years that in order to “make a safer cigerette” all you have to do is mix in some marijuana extract.

    However, they would rather lie to our faces and say completely dumb things like, there is no way to make a “safer cigarette”, which is just the excuse they use in their own heads for lacing poisons into the cigarettes to increase their addiction potential and make them kill you faster.

  23. Most people do not know almost any Herb can be “smoked” or “brewed for Tea”; take the common Mullein Plant: flowers are used for Tea; the roots are boiled for syrup; the leaves are smoked by American Indians; the soft velvety leaves line the Indian Moccasins.

  24. I was reading “smoking Mullein or using Tea” actually “clears the lungs”! Indian Tobacco !
    (I would use the Tea; buy @ store or grow mine

    Mullein can be used as a short acting candle:
    other names: Aaron’s Rod and Indian Flannel; because the leaves are soft like Flannel…
    Mullein is a tall weed seen in fields/meadows.

  25. I would be interested in finding out how to make topical and or tinctures + extracts…
    my brownies came out like “stones; I ate them anyway; fed some to the birds; Brownies are expensive to make; Weed is way to0 expensive!!

  26. Your over cooking them for one. Turn the heat down, learn to grow.
    Brownies will harden very quick.Make cupcakes.

  27. “Why on God’s green earth, don’t they try to regulate on a legal level? Prohibition of cannabis makes no sense at all. Pharmaceutical companies? They will eventually lose some of their money, as public opinion changes, and the majority of Americans demand fair laws. They might as well give in, and then move on. They’ll find other ways to make money.”

    Yeah, but if you count hurting people as part of your profit, there is muck less profit for you in legal regulations that make sense. Where is the opportunity to harm an innocent person under that law??? How can you turn around and use marijuana as an excuse to put people in jail if it is legal and well regulated? The primary goal of marijuana prohibition is to lock up and otherwise harass innocent people and steal their money.

    Unlawful arrest and detention.

    Stealing of money from the general fund and directly from arrested victims; often expressly used to maintain the fiction marijuana is a “bad drug”.

    Everyone is the government is taught to have a bias against marijuana. Nearly all government jobs piss test. These folks already have a sheeple mindset. The judges look at the situation like, “well if I don’t have this right, why would I defend and thus extend it to someone else?”

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