Study Says Smoking Marijuana Worse for Lungs than Cigarettes

Smoking a single marijuana joint is equivalent to smoking 2.5 to 5 cigarettes in terms of damage to the lungs, largely due to differences in how pot and cigarette users smoke.

The Guardian reported July 31 that researchers at the Medical Research Institute of New Zealand found that the deep drags taken by marijuana users, along with their penchant for holding smoke in before exhaling, can cause problems like obstructed airways and hyperinflation of the lungs. The lack of filters on marijuana joints also contributes to lung problems, researchers said.

The study involved 339 adult volunteers divided into four groups: marijuana-only smokers, tobacco-only smokers, marijuana and tobacco smokers, and nonsmokers.

All of the smokers reported coughing and wheezing, but only tobacco smokers exhibited signs of emphysema.

The study was published online in the journal Thorax.

31 Responses to Study Says Smoking Marijuana Worse for Lungs than Cigarettes

  1. terris harmon | February 24, 2013 at 5:32 pm

    Don’t wanna smoke anymore

  2. carla | April 26, 2013 at 1:20 pm

    i belive that weed does not affect as much as cigarettes! because first my teacher told me. and second of all…….. forget it.

    • Chris | August 16, 2013 at 11:39 pm

      You defy scientific research and common logic? You are in what is called “denial”.

      • Driaan | November 22, 2013 at 10:09 am

        any highschool senior should be able to identify Di-Hydrogen Monoxide as WATER.

      • some guy | December 12, 2013 at 10:35 pm

        but “scientific research” backed buy the company that is advocating one product is never trustworthy science, they will always take the numbers that support their claim and disregard the numbers that prove them wrong.

    • Bob Marle | August 17, 2013 at 8:26 am

      I’m not saying either one is good, but, somebody got the brilliant idea to mislead kids in regard to both Tobacco and Marijuana. Every breathe you take contains Methane, it’s a natural part of air, admittedly in small amounts. Your body, for instance your blood contains urea, Nicotine is one of the reasons cigarettes are addictive, it’s not what kills you. There are alot of carcinogens in cigarettes. Generally smokers die from damage to the Cardiac or Pulmonary systems in the form of cancer,strokes,heart attacks, Lung Cancer,….Since I was in high school, I’ve noticed something, more and more people are using longer papers to roll there joints (I’m in College, I’ve seen 3 out of 5 smoke pot). If anti-smoking groups and anti-drug groups didn’t lie and exagerate, there would be much less drug use by minors. To understand, ask yourself, what is fire? Fire or combustion is a chemical reaction, Tobacco does give off more chemicals. What I find interesting is that not one search turned up the actual number of chemicals released when Tobacco or Marijuana combusts, this is a text book only a med student would have. The bottom line for me is that the key to life is moderation, impulse control. Drugs will make you feel great, and after the first time someone uses them the next day they think about all the bullcrap they were told and forget every bit of it. I mentioned urea and Methane because you did but the anti-smoking group truth, were asking people which fact is grosser “the fact that cigarettes contain urea which is in cat pee or that Methane is in Cigarettes and dog crap, Your in constant contact with both at all times. Di-Hydrogen Monoxide kills thousands of babies every yearDHMO is found naturally in fruit. When inhaled DHMO can kill an adult in minutes, even though DHMO is not regulated, DHMO is often used by marijuana smokers, they use it in special pipss to enhance the experience;, everything I said is true, try googling DHMO or Di-Hydrogen Monoxide. The group Truth is like the brady campaign. Mislead, lie do whatever it takes for what they are against, where the end justifies the means. Once again I’m not saying you should start, but, ask questions, don’t be intimidated

    • natalie | January 9, 2014 at 12:23 pm


  3. Wisdom | July 9, 2013 at 2:29 pm

    This is completely untrue.
    Tobacco is an aliotrophic plant that contains Nicotine, which has 8 times the toxicity rate of rattlesnake venom, and cigarettes contain urea and methane.
    Cannabis/Marijuana is a flowering herb with a solid bud. The herb contains 80 different cannabinoids, the most important being 9-delta-tetrahydrocannabinol, or THC. THC has no LD50 and therefore can -not- be overdosed on. The USA ran an experiment where they put masks on monkeys and pumped them full of 30 grams of marijuana smoke; that’s over $200 worth of marijuana at once. After several experiments the monkeys died of brain atrophy from suffocation with 0 visible effects from marijuana.

    If you believe in God, then read the bible. God gave us Marijuana.
    “And God said, Behold, I have given you every herb bearing seed, which is upon the face of all the earth, and every tree, in the which is the fruit of a tree yielding seed; to you it shall be for meat.” Genesis 1:29

  4. James | July 24, 2013 at 12:29 pm

    My aunt smokes around a pack of cigarettes a day and is always going back for more and more. Cigarettes are very addictive mentally and physically and I hear my aunt coughing all the time from smoking. But with marijauna yes you do cough but when your smoking and after you hit whatever your smoking out of because it’s not filtered, and cigarettes have about 4,000 chemicals.

  5. bobby | August 8, 2013 at 6:05 pm

    Really? a 339 person study? and they think they can apply this to the 16 million plus marijuana smokers in America? Idiots, this isn’t science, this is propaganda.

  6. Jhunda | October 3, 2013 at 1:11 am

    I would like to see this ‘proof’. Look at a weed smokers lungs after YEARS of smoking.. looks normal. It hurts your lungs cause in this study they just held their breathe for a long time and lost oxygen.. thats what holding your breathe does. its not the weed.. its just people trying to keep weed illegal (mo’ tickets (+3475438698 other things) mo’ monies)

    secret to life: follow the monies

  7. Jay | October 6, 2013 at 9:15 pm

    anyone else notice how this article is meant to say marijuana is worse than cigarettes, but the end it discusses tobacco-only users, not marijuana-only users?

  8. reaper919 | October 7, 2013 at 2:08 pm

    every one remembers being in high school when pot hits the students. i am 21 have never done pot have thought about the negitives and positives of both i fermly belive that pot is a lot better for you in the long run pot is a plant the is not main stream comersalived it dosnt have tarr it dosnt have half the cemicals in it a cigs i understand that it must be ilegal for a reason but its legal in colorado and becoming more accepted in groups between the substancel amount of people the some cigs and the same # of people that smoke weed i have seen people die in my own family from cigs and i know people that smoke weed that are now 42 the are in great health uyou shouldnt smoke ever way it screws uyou up eather way but i u do pick pick weed

    • Kubar | November 21, 2013 at 7:19 am

      Actually weed is not so bad; weed does have tar, but tar alone is not bad. People can easily cough tar up, and tar alone doesnt do much harm; it is only harmful when you cannot cough it up.
      Weed actually has more tar than cigs, but cigs have chemicals in them which make our lungs close up- this causes a build up of tar- which is bad.
      Weed on the otherhand has no chemicals added to it, and actually opens out lungs up more, and make them more sensitive: this is why after smoking weed people cough- it makes our lungs (temporarily) more sensitive.
      This actually helps- because it makes us cough we can easily get rid of the tar.

      The only reason Weed is (still) illegal is because a lot of people would loose a lot of money from it- There would be no need for most pain relieving medicine, not to mention all the other drugs that would not be used because of weed.

      • me | November 25, 2013 at 5:29 pm

        Please don’t talk about something you have no idea about. Marijuana has no tar. Tar is bad for you, it contains the most potent carcinogen, or cancer causing substance, in cigarettes. You cannot cough up the tar you get from cigarettes, and the closing of the lungs has nothing to do with what tar does to your lungs. When the lungs close, that causes emphysema, which is a totally different disease where air gets trapped in your lungs. You might be right about marijuana increasing the sensitivity of your lungs, iv’e never heard about something like that, but that has nothing to do with coughing up tar. Also, most chemicals in tobacco are found in the plant itself, and how are you sure that the marijuana you bought from the shady street vendor doesn’t have anything other than marijuana in it? With cigarettes you at least know that whoever made it knows what they’re doing. I’m not saying that cigarettes are better, because they’re not. I’m just saying that marijuana is very bad for you.

        • Joe Johnson | February 11, 2014 at 3:42 pm

          Oh, sweetie. You clearly don’t understand how the drug industry works, no one gets their ‘dro from some random on the street. This isn’t 1982.

  9. Chris | October 24, 2013 at 4:59 pm

    Jan. 11,2012 —Using marijuana carries legal risks, but the consequences of occasionally lighting up do not include long-term loss of lung function, according to a new study in the Jan. 11,2012,issue of the Journal of the American Medical Association. This was one of the largest and longest studies ever done on pot. The name of this website leads me to believe there may be some bias hear…. or maybe its just the reefer madness kicking in.

    • Josh | November 3, 2013 at 1:36 am

      Well, their first mistake is that they even mention marijuana on a site called “drugfree”, as it is not a drug. Ignorance is hard to annihilate these days. There is no legitimate scientific “study” that proves marijuana smoke can be even close as harmful to lungs as tobacco, let alone more harmful… I’m not even gonna start about addiction. People are being poisoned by propaganda every day. The public needs to know that cannabis, magic mushrooms and LSD are NOT harmful. Call them drugs or whatever, but they will never do any damage to your body like general pharmaceutical drugs do.

  10. Robert Vaughn | November 14, 2013 at 9:50 pm

    Not to take everyone’s attention off of the study’s results, but they say 339 people divided into 4 groups? That’s not possible. That would be 84.75 people, who’s the .75?

    • me | November 25, 2013 at 5:29 pm

      they never said equal groups

  11. some guy | December 12, 2013 at 10:27 pm

    This study is a bold faced lie funded by the tobacco industry.

  12. stupid internet | December 21, 2013 at 7:00 am

    come on, we all know ciggarettes are more harmful unless the marijuana is mixed with windex or other chemicals. Also people who are talking about DHMO (dihydrogen monoxide), it is not true. DHMO is IUPAC name for water. Please stop spreading false imformations.

  13. Andre | January 12, 2014 at 1:00 am

    the January 2014 issue of this magazine THORAX; studies are showing that COPD is caused by the deep inhalation of KB because people hold their hits in longer and it expands when you cough. Jock boys quit swim team and workouts shortly after they start to hangout in stairwells and start getting stoned. After a while your values change but so what. That is why a few years ago nobody wanted to legalize dope and now nobody cares because we are all stoned. After a while you start snorting pills and shooting smack. That is why these people want us all drug free. Are you going to prove them right?

    The study has one young white guy, and a few cab drivers that hardly smoked any tobacco at all and they had the same damaging effects in 15 years of toking up refer. It said 3 or 4 joints is equal to one pack. So for sure Don’t smoke any tobacco if you like to smoke pot. Be sensible you don’t need a scientist to tell you this stuff. It is common knowledge. I am kinda middle of the road. I got busted with a pack of papers so I lost my teaching license. It could have been worse.
    I actually got a break the way I look at it.

    Teachers don’t really have competency test and they don’t test us like nurse, but we have to drive sober and get up at 5 am and do our lesson plans. Some of us got C’s but we had to learn this stuff in the first place. It is a difficult life trying not to get a traffic citation or avoiding restaurants that serve liquor.

  14. GrumpyDude | January 24, 2014 at 11:50 pm

    Luckily smoking is not the only way to ingest it.

  15. Alex | February 7, 2014 at 10:37 am

    I’m sorry, but if your only reference is from a study done in 2007 I can not find your findings credible. Also, if you look at the full text of the study anywhere it says “of” is in red. What is that about? It doesn’t seem legitimate to me.

  16. Joe Johnson | February 11, 2014 at 3:38 pm

    This is a blatant lie. The act of smoking in of itself is harmful to the lungs because you’re inhaling dried plant matter; that being said marijuana is not addictive (like cigarettes), does not cause cancer (like cigarettes), and does not cause heart disease (like cigarettes). Literally every other study ever conducted has proven medical benefits of marijuana; to claim the exact opposite of a known scientific fact is duplicitous and harmful to the public.
    You should actually be ashamed of yourself.

  17. steven | April 7, 2014 at 12:04 am

    This is quite funny how many people are so misinformed about this tobacco the plant is not harmful until smoked and yet it also depends on how it was cured and made by the farmers also pot is also a plant tobacco and weed are plants when burned they give off tar which contains majority of carcinogens in tobacco therefore also pot and pot smokers hold the smoke in and yet is unfiltered so has more tar in it also to get tar you need to combust it plainly light it on fire otherwise you don’t get tar smoke is smoke no matter what u burn tobacco contains naturally more chemicals in it which during combustion makes about 200 chemical compounds if I’m correct 4000 chemicals when combusted turns to chemical compounds chemistry 101 weed is better for you then cigs but if you do reaserch not by much yes weed can cause cancer to those ignorant misinformed people but not as high alot a chance and weed can be addictive pshycologically not physically nonetheless addictive just eaiser to quite do reaserch

  18. J | April 10, 2014 at 1:21 am

    I can’t find this study, where’s the results that show this because other studies are showing the opposite

  19. sebas | April 10, 2014 at 3:51 pm

    i beleive that it says ciggarrete caused emphysema, whereas weed was left apart so one can assume that weed does not cause this since the research didnt state nuthing. i wonder what happens whn u smoke weed with tabacco and just weed in a pipe, i hope theres no difference. just weed makes it better worth is my guess, hope weed is fine : -)

  20. chad | April 13, 2014 at 4:42 pm

    It is an empirical fact that alcohol is more lethal and dangerous than cannabis. The moral equivalence of condemning cannabis in society while approving alcohol is hypocrisy. Alcohol overdose can be fatal and According to the center for disease control there are 88,000 deaths attributed to excessive alcohol use alone not including accidents and driving. With prescription drugs there is a fatal overdose every 15 minutes while there has never been one documented fatal overdose with cannabis. There are no statistics for cannabis deaths as there are none. How can this be? It’s been in widespread use in the US for over 50 years now and in civilization for over 5,000. Surely if this substance is so dangerous we would have evidence in the year 2014. The government says this substance is just as deadly as heroin, crack, and methamphetamine and those are obviously dangerous and indeed deadly and no one would argue for reclassification but does cannabis belong in schedule 1 in the CSA? Does any unbiased physician believe that cannabis belongs in this schedule? Why is alcohol not in this list? It seems that is has a high level of abuse potential and actually does kill people and definitely does not have any medical benefit.

    The main physical harm from cannabis is from combustion and smoke to the lungs. That has always been a major concern for me and now there is a way to completely avoid the carcinogens through vaporization. In fact I haven’t smoked in years and my lungs feel great and I never have any sinus problems, coughing or bronchial issues. Being that your a Pulmonology specialists you must be aware of the largest long term study to date on marijuana smoking and it’s effects on the lungs by Donald P. Tashkin MD at UCLA. He found that there is no link to marijuana smoking and lung cancer. There was even a very minor decrease in lung cancer than the non-marijuana group suggesting cannabis could have some sort of protective property. There have also been studies in mice who were injected with thc that showed tumor growth was inhibited by 60% in THC-treated mice compared with vehicle-treated control mice. That is directly from the web site. Anyone who thinks cannabis has no medicinal benefit need to look no further to Federal government’s patent on cannabis a therapeutic “Patent No. 6630507: Cannabinoids are found to have particular application as neuroprotectants, for example in limiting neurological damage following ischemic insults, such as stroke or trauma.” How can the government deny the benefits of medical marijuana even as it holds a patent for those very same benefits?

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