Does weed cause lung cancer?

We don’t know if weed causes lung cancer yet. But marijuana use and cancer risk are associated. Learn more about lung cancer and marijuana here.

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Maybe. But right now we do not know precisely if marijuana causes lung cancer, or not.

In fact, some studies offer different conclusions about the relationship between marijuana and cancer. One study indicates that long-term cannabis use increases the risk of lung cancer in young adults. While other studies suggest that the association of cancer with marijuana, even long-term or heavy use, is not strong and may be below practically detectable limits. Read on to learn more about the carcinogenic properties of marijuana and how marijuana impacts the lungs. And PLEASE ask your questions about marijuana use below. We’ll be happy to respond to them!

Is marijuana carcinogenic?

Yes, marijuana is carcinogenic (has the potential to cause cancer). In fact, marijuana smoke contains 50 – 70% more cancer causing compounds than tobacco smoke. And because marijuana users usually inhale more deeply and hold their breath longer than tobacco smokers do, they increase their lungs’ exposure to carcinogenic smoke.

So doesn’t that mean that marijuana can cause lung cancer?

Well, the short answer is maybe. Marijuana CAN cause lung cancer. But smoking weed (even daily) has not yet been associated directly with the development and outcome of lung cancer. In other words, not enough people who smoke marijuana have developed lung cancer in order for experts to define the relationship as causal. Although we know that marijuana affects the immune system, the implications for its impact on cancer are unclear.

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How marijuana affects the lungs

WE DO KNOW that marijuana affects the brain and that memory loss smoking weed is common. But how does marijuana smoke affect the lungs? Simply, marijuana smoke irritates the lungs. In fact, smoking marijuana increases the risk of respiratory problems. This is because as you smoke and inhale weed into your lungs, you also inhale carcinogens and other toxins. A recent study reported that people who smoke marijuana frequently (but not tobacco) have more health problems and miss more days of work than nonsmokers. Many extra sick days among marijuana smokers are for respiratory illnesses. Repeated exposure to marijuana smoke can lead to a number of medical conditions such as:

  • excess phlegm production
  • lung infections
  • more frequent acute chest illnesses
  • repetitive, chronic cough

Tobacco (in your spliff) and lung cancer risk

If you smoke weed and add tobacco to your spliff, you are at increased risk of developing lung cancer. The fact is that many people who smoke marijuana also smoke cigarettes and cigarettes DO cause cancer. In fact, cases of lung cancers are often more likely than controls to have smoked cigarettes and to have used alcohol heavily in addition to smoking pot. So, although lung cancer cannot be linked to marijuana per se, cigarettes can. And if you are rolling your joint with tobacco, this tobacco can cause lung cancer.

Why you should avoid smoking marijuana

Is weed good for headaches and other medical conditions? Yes. Marijuana can actually be helpful and is prescribed for a number of different medical conditions ranging from glaucoma to cancer treatment. This is why some experts recommend that you avoid smoking marijuana for medical purposes, and instead use synthetic THC compounds that you take orally for the therapeutic potential of pain relief, nausea control, appetite stimulation, and decreasing ocular pressure.

Questions about smoking marijuana

Studies HAVE NOT YET found an increased risk of lung cancer in marijuana smokers, as compared with nonsmokers. But smoking marijuana can impact your health for the worse. Do you have a question about smoking marijuana and your health? Please leave it below. We answer all questions personally and may even respond by writing a new article!

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Reference sources: Marijuana: Facts Parents Need to Know from NIDA
Marijuana Use and the Risk of Lung Cancer
and Upper Aerodigestive Tract Cancers: Results of a Population-Based Case-Control Study
Womens Health [dot] gov on How To Quit Smoking Marijuana
American Lung Association  publication on”Hazards of Smoking Marijuana”
NIDA Info Facts on Marijuana
Cannabis use and risk of lung cancer: a case-control study
Epidemiologic review of marijuana use and cancer risk
About the author
Lee Weber is a published author, medical writer, and woman in long-term recovery from addiction. Her latest book, The Definitive Guide to Addiction Interventions is set to reach university bookstores in early 2019.


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  1. Just remember….all sources used to claim that smoking tobacco was a healthy pastime….I for one have no prejudice regarding pot use but I do have an issue with smoking….stop lying to yourself and find another way to injest it….brownies, cookies, etc ad infinitum….enjoy but spare your lungs ….you will miss them….

  2. I’ve been smoking for over 9 years, bongs,blunts joints gravity bongs, apples, potatoes heck even aluminium cans, with that being said. I have a few times we’re I forget what I did last year, besides that I breath fine they must do research on cannabis that is grown in the worse possible way, it’s like buying milk with Rbst treated cows catch ma drift? No addiction, just smoke as i go no time wasted.

  3. My friend started smoking when he was 11 and now he is 17 years old. He is highly addicted to it. He smokes everyday. 6 – 20 times a day. I am worried for him. Does he have a chance of having lung cancer?

  4. marijuana is good and should pe legal all over the world and dont smoke it enjoyed delicious pastries like cookies and rice kryspie if you dont want to get lung canser.

  5. When you say “In fact, marijuana smoke contains 50 – 70% more cancer causing compounds than tobacco smoke,” are you referring to smoke from tobacco in its natural and simply dried out form, or in its cigarette version after dozens of chemicals have been added to it?

  6. Every one of your “reputable” sources has been disproved by numerous legitimate scientific studies from universities such as Harvard and Yale, just to name a few. Specifically, the NIDA and American Lung Association have been repeatedly shown to be biased and propaganda filled.

    You’re website can do some legitimate good and really help people, but much like programs such as D.A.R.E. attacking marijuana only makes you seem ignorant and biased as more and more of the world wakes up to realize they’ve been lied to for decades. You do yourself a disservice by allowing outdated lies like this article to exist.

  7. Having read through numerous messages written here on this page. I get the impression, that a lot of people have an argument against marijuana, due to their experiences with it in the past. Them experiences were most likely formed, from the fact that it was and has been illegal since the 1930s. To outlaw the creation of God! Makes no sense to me. How many studies and or investigations took place before outlawing in the 30s? Not enough obviously! Take note the native used to smoke marijuana for many medically,and spiritual conditions. So for all those ignorant people who have been convinced by the government that marijuana is a drug and or harmful, really shouldn’t speak on the matter. It’s people like you who affect, mine and several million others conditions. We got so many man-made medicines in this world that causes so many side effects and have so many harmful risks. Where’s the argument there? Where’s the argument with the man-made alcohol that we sale in every convenient store? Because nobody understands the amount of deaths that occur every year,each day from the effects and the use and abuse of alcohol. There are no recorded harmful effects from marijuana. The lung cancer or short-term memory loss, accusations against marijuana, upsets me. Allow me to be realistic! If anyone claims marijuana is harmful, there the foolish ones. I smoked it 20+ years Ever since I was a boy. The only illness it has ever caused me, is that ill feeling I have when I don’t have it. So for all of you who have a disagreeing opinion on medical marijuana, and the good it does for so many people. They should do everyone including God, a huge favor . And quit ridiculing the use of marijuana! If you’re looking for a debate, you should focus on the matter of alcohol and or prescription drugs? Or even tobacco! Right ? Those issues all have recordable and verifiable harmful and in some cases fatal affects. Shouldn’t we spend our energies towards the problem rather than the solution. Marijuana is a solution for several conditions, and to contest that to me only seems hateful .,,,,

  8. I don’t smoke it regularly anymore, but I definitely have a greater lung capacity when I do. I have mild asthma. I am also often anxious, so maybe that is connected to being able to breathe deeper, I don’t know. I found this article to be much more of an opinion piece than an informative article, and the fact that the author asked the first commenter if he smoked weed was highly unprofessional.

  9. My husband smoked marajuana for 42 years and just passed last May 14th of urine bladder cancer. I’ve never read this but I think that you end up swallowing a lot of carcinogens from the smoke being inhaled and mixing with the saliva in your mouth. Has there ever been a study to see if there is an increase of bladder cancer with marijuana smokers? It also caused a a lot of problems with raising our boys. Very confusing for young boys to have a father that smokes it yet it’s illegal. Caused a a lot problems in my marriage. Causes a lot of phobias as to whether someone would find out. It’s really bad situation all around. My husband regretted smoking it basically all his adult life and repented of it on his death bed, begging his one adult son to stop destroying his life and to start acting responsible and working hard to make something of himself before its too late. I pray others can see the truth that it controls you and it’s nothing but bad news.

  10. Dan B — I have been smoking pot pretty much on a daily basis for 44 years and have NEVER coughed up black tar. Hopefully, I can continue to afford and access it for the rest of my life. I am a much happier, calmer and peaceful person with it, than without. Personally, I worry more about those poor deluded souls pounding the pavements (jogging) along major roadways, snuffing in all those car emissions in the name of ‘good’ health.

  11. You all sound like me (an addicted fool) while I was hooked on the MJ.

    A bunch of addicted fools here.

    Think about this… let’s forget about all the chemicals and shit that could or could not be in marijuana.

    Let’s just focus on the smoke.

    Do you REALLY think the delicate and soft tissue within your lungs can withstand being smoked daily for years on end?

    Think about what happens to meat when they smoke cure it. You are essentially doing the same thing to your lung tissue.

    Lastly, take a look at all that black shit inside your bowl the next time you smoke.

    Do you really think that stuff isn’t coating the crap out of your lungs. Your lungs are completely coated with that junk.

    I quit smoking 2 months ago and I’m still hocking up black tar every morning.

  12. Marijuana is a TRUE curse.

    It ruined my life and stole my childhood along with most every person that I know..

    Anyone that claims otherwise is either addicted or profiting from illegal sales. 50 years in Humboldt – I’ve seen it ALL and it’s nothing but bad news. Have known several people with cancer and the weed did not keep them from dying. It’s all a lie. Don’t be a fool. 🙂

  13. What about the use of marijuana to help treat vertigo? I am taking meclizine but do not the side effects(can cause liver /kidney damage , constipation , etc.)

  14. Hi Sheila. You can call 1-800-662-HELP to reach the National Drug Abuse Hotline and talk with a counselor about taking steps to help your son address possible addiction to Spice. Or, you can talk directly with a psychologist or licensed clinical social worker with experience in treating family addiction issues and start looking at options. Either way, help is out there.

  15. I’ve quit after some difficulty. There is no withdrawal, just cravings for about 3 days. And I can go back to it after a few months, a year, whatever and enjoy much less of the plant.

  16. “We did not observe a positive association between MJ use — even long-term, heavy use — with lung cancer.”

    “Marijuana use does not cause or potentiate emphysema in any way.”

    Dr. Donald Tashkin, M.D., UCLA
    Marijuana and Lung Cancer: Results of a Case Controlled Study

    “Marijuana, in its natural form, is one of the safest therapeutically active substances known to man.”
    – Francis L. Young, the DEA’s Administrative Judge himself
    Marijuana Rescheduling Petition Sept. 6, 1988

    All the links here are from the Institute on Drug Abuse and Drugfree, what do you think they’re going to tell you? Note the constant, mandatory use of the words “may” “should” “can” and “could.” Not to mention, these were lab rats.
    Don’t give in to the lies, people. Let only the truth guide your decisions. Read Marihuana Reconsidered, by Harvard Medical Professor Dr. Lester Grinspoon M.D. and watch the documentary The Union, directed by Brett Harvey, and educate yourself about a government that does not care for you. 400,000 deaths a year from (government-funded) tobacco. 0 from cannabis.

  17. Hi Katie. Thanks for your comment. You make a good point. While I cannot find government helplines specifically addressing marijuana cessation (they exist for cocaine and heroin use), you can call the National Drug Abuse Hotline at 1-800-662-HELP and ask for guidance. Best of luck!

  18. I am 26, and I have been a heavy marijuana smoker for 10 years now, (about 3-4 joints a day) and I now have a bad cough.. Not sure how long I should let the cough go, before I become concerned it could be a sign of lung cancer or other illness… I was also exposed to second hand smoke my entire childhood. I wish I could stop smoking, but I find it nearly impossible, I guess after all these years, I am somewhat addicted. I know they have alot of support out there for people who want to quit tobacco, but what about people who need help quitting marijuana?

  19. This article claims 50 to 70% more carcinogenic compounds in cannabis than tobacco. That’s simply a lie.
    Cannabis is natural and usually smoked alone.
    Tobacco from cigarettes is one of over 400 ingredients like ammonia, high fructose corn syrup, artificial flavoring, saltpeter, etc.
    Based on simple math, once cigarette is more carcinogenic than smoking cannabis for a year.
    The compounds in cannabis smoke do not bond to the human body (throat, lungs in particular) the same way as tobacco smoke. Furthermore, tobacco is grown in irradiated soil and has a half-life of 25 years.
    If cannabis is so dangerous, why must you lie about it?
    To continue, the statistic 50-70% instantly sends up a red flag to anybody used to doing investigative research.
    The red flag is: Why is there a 20% margin of error?
    The reason that percentage is used in the first place proves that there is no conclusive evidence that cannabis smoke contains that much more carcinogens.
    In fact, research proves the opposite, but this is not my forum so I’ll stop here for now.
    But one more thing: This article is filled with so many contradictions. I really hope that nobody suffering from or denying addiction looks for help from this article.
    The section Why you Should Avoid Smoking Marijuana starts by listing known benefits of cannabis, then saying that smoking is not the best form of ingestion. Although the research and clinical studies (not shown here, curiously enough) of synthetic THC or THC/CBD treatments such as Marinol prove that it has a much lower range of effect on patients, while also being effective for way less than 60% of users.
    Smoking or eating cannabis is the best method of ingestion for any
    Cannabis smoke helps break up mucus and relieve symptoms of tobacco-related build up, phlegm, irritation, etc.
    Similar to the plant Mullein. Since Mullein doesn’t make you high, nobody lies about it.

  20. I looked into a lot of science sites and they all say thanks to thc it cant cause cancer basically. Theres yours short answer so no and in fact it kills the old cancer cells so it keeps u from dieing from cancer and ma by cure it.

  21. Hello Osiris. The reference sources for this article are listed at the bottom. All information and data comes from reputable and trusted institutions, like the American Lung Association, or the NIH’s National Institute of Drug Abuse. Out of curiosity, do you smoke weed?

  22. NoIn 2007 Harvard actually did a study on this very question, they found that THC actually fights of lung cancer and can be used as a combatant. Later a group in Europe did the same test a few years later on mice that had been implanted with cancerous cells and then injected with THC and what do you know the cancer was actually in remission. It is true, marijuana (when smoked) does introduce more tar in your body than cigarette smoke, HOWEVER and that is a big however, there is still no proof or research that has concluded in Marijuana giving you anymore of a chance to contract cancer…In fact marijuana smokers have been said to be less prone to cancer and those who smoke marijuana have 20-30% better lung capacity then those who don’t…this has all been researched and is public information. Not sure where your information came from but it is not fact and should be deleted and or corrected.

  23. Hey there are stuies that marijuana does not cause cancer. Now they have discovered it is the cure for cancer. Check out the stuff on Marijuana Planet all kinds of research there.

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