Does Smoking Weed Cause Lung Cancer?

Sophia Delphi May 14, 2022 - 7 min read
Fact Checked
Illustration for Can Smoking Weed Cause Lung Cancer

In 1964, after the U.S. Surgeon General warned that cigarette smoking caused lung cancer, an enormous number of smokers either didn’t believe the warning or didn’t take it seriously.

It actually took decades before the number of smokers fell dramatically. In 1965, 42% of American adults smoked. In 1974, 37% still smoked; in 1983, it was 32%. And it wasn’t until 2010 that the number dropped below 20%. The smoking rate is now around 14%.

So it took 50 years, but the association between smoking and lung cancer finally had a big effect. (So did huge taxation, but that’s another story.)

The federal government’s inexplicable battle against weed has lasted well over 80 years. But they’ve never made a similar pronouncement that marijuana smoking causes lung cancer – which might have (very) slowly reduced the use of the demon weed.

It doesn’t take a degree in medicine or government policy to understand why: there’s no solid evidence that smoking weed causes lung cancer.

Does that mean there’s nothing to worry about when you toke up? Unfortunately, that conclusion goes too far.

Here are the facts.

What We Know About Smoking Weed And Lung Cancer

It’s not a lot.

We do know that cannabis smoke contains many of the same carcinogens as cigarette smoke; some experts estimate the commonality to be about 30%. And weed smoke has a much higher concentration of some of those carcinogens, like benzanthracene and benzopyrene. On the other hand, that means marijuana smoke doesn’t contain 70% of the problematic substances that are in tobacco smoke.

We also know that the two types of smoking aren’t the same. Weed smokers usually inhale much more deeply but don’t smoke as frequently as tobacco smokers.

So there’s no direct correlation between the two – meaning we have to rely on scientists to supply more detailed data. But that data isn’t particularly helpful, either.

A group of experts looked at the existing evidence and summed up the problem in the Journal of Thoracic Oncology a few years ago.

Basically, they said the studies that have been done so far aren’t reliable due to a number of factors: they’ve involved very few smokers, those who have participated in “self-report” data on their cannabis use, very few admittedly-heavy smokers have been surveyed, and many participants also smoked cigarettes as well.

Why was that criticism even necessary? It’s because the studies come to very different conclusions.

  • One report published in the journal Cancer Epidemiology, Biomarkers and Prevention concluded that existing research showed no association between marijuana use and lung cancer and that cannabis might even help protect against lung cancer.
  • A later study published in the International Journal of Cancer said researchers found a possible connection between weed use and one form of lung cancer (adenocarcinoma) but not another (squamous cell carcinoma). It concluded that the association between habitual weed smoking and lung cancer was minimal.
  • Work published in the European Respiratory Journal did find a link between long-term marijuana smoking and lung cancer in adults younger than 55, with heavy smokers having a greater risk.
  • And another published study in the Journal of Thoracic Oncology found that male tobacco smokers had twice the risk of developing lung cancer if they also smoked weed.

What can we conclude from all of these scientific studies? Simply that more, detailed research is necessary before anyone can conclusively state that smoking weed doesn’t cause lung cancer or even contribute to it.

What’s equally clear is that the likelihood of contracting lung cancer from cannabis smoking is far lower than it is from cigarette smoking.

And one more fact is clear: marijuana smoke does do damage when you inhale it.

The Effects Of Smoking Weed

Image of Fingers Holding Smoking Weed

There are small, hair-like structures in the respiratory tract called cilia, whose job is to clear foreign particles from the airways. And research has shown that both cigarette smoke and weed smoke cause damage to the cilia.

Smoke also causes the body to produce more mucus. The cilia are supposed to help clear mucus from the bronchial tract – but when they’re damaged, they can’t do it as effectively. That’s one of the reasons behind the “weed cough” we’re all familiar with.

There’s another common reason for the coughing, as well as the sore throats you may suffer when smoking. Smoke, of any kind, irritates tissues in the throat and lungs. It can cause wheezing and chronic bronchitis in cannabis smokers as well as cigarette smokers.

One more issue to consider: signs of cellular damage and pre-cancerous lung conditions have been seen in some long-term, habitual marijuana smokers.

All of that, obviously, is not great. But should it be overly concerning?

We have some good news to pass along on that front. Lung function doesn’t appear to be compromised in the vast majority of weed smokers. In fact, studies claim that cannabis smokers have no greater risk of developing COPD (chronic obstructive pulmonary disease) than the general population. And there’s some evidence that smoking weed may actually improve smoke peoples’ lung capacity over time.

Here’s more good news. Research-based on organ transplant results has shown that lungs taken from regular weed smokers functioned just as well as lungs from non-smokers, once they were transplanted into patients. It further suggested that cannabis users’ lungs (after they’ve passed away, of course) should be made available to organ transplant patients.

That’s a lot of information. What does it all mean?

So Can Smoking Weed Cause Lung Cancer, Or Not?

No one knows for sure.

Any possible link between the two is far from the obvious causal relationship between cigarette smoking and lung cancer. And there’s no firm evidence that weed smokers are at enormous risk of developing lung cancer.

However, cannabis smoke does cause some damage to the respiratory tract, and there are indications that it may contribute – at least, somewhat – to the possibility of developing lung cancer over the long term.

What’s a poor weed lover to do?

There are two choices. One is continuing to smoke while waiting to see whether further research can nail down the connection (or lack of connection) between marijuana smoke and lung cancer. The other is switching to edibles, tinctures, or another form of cannabis consumption that doesn’t stress the lungs in any way.

Can Smoking Weed Cause Lung Cancer? FAQ

Q: What about vaping weed? Is that a good way to avoid or minimize the risk of lung cancer?
A: The answer is the same as it is for smoking: no one knows for sure. It’s been documented that vaping nicotine or cannabis can cause lung damage, and there are early indications that vaping nicotine is a safer option than smoking cigarettes. But there’s not enough evidence to know whether there’s any link between ordinary vaping and lung cancer, let alone vaping marijuana.

Q: Is there any way to minimize the risk of lung cancer if I don’t want to quit smoking weed?
A: Yes, don’t smoke tobacco. Tobacco has been definitively linked to lung cancer, of course, but there’s some evidence that cannabis smokers who also smoke cigarettes may run an even greater risk.

Q: But doesn’t THC help fight cancer?
A: There’s no proof of that, other than the results of the single study we mentioned earlier. Medical marijuana has been used by cancer patients to help deal with the side effects of chemotherapy for quite some time, and early results of animal research indicate that THC may help fight some types of cancer. But those same studies also show that it may accelerate the growth of other types of cancer, and there’s no definitive evidence at all regarding weed’s effects on lung cancer.