Key takeaways:
Smoking cannabis damages and irritates the lungs. This can lead to a chronic cough, mucus production, wheezing, and shortness of breath.
Cannabis smoke contains some of the same cancer-causing toxins as cigarette smoke. Smoking cannabis with tobacco is the most harmful way of using it.
The long-term effects of smoking cannabis on the lungs aren’t clear. More research is needed to better understand the risks.
Use of cannabis (also known as marijuana) is increasing in the U.S. And, despite the growing number of ways to consume it, smoking is still the most popular.
You’re likely aware that smoking cigarettes and vaping are bad for your lungs. But you may not be aware that smoking cannabis can also damage your lungs. So, how does this risk compare to smoking cigarettes or vaping?
Here’s what the latest evidence tells us about the effects of smoking cannabis.
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How does smoking cannabis affect your lung health?
Smoking any substance can cause inflammation in your airways and lungs. Any substance that is burned releases toxic chemicals. When you inhale those chemicals, it causes direct and immediate irritation to the lung’s delicate tissues.
Cannabis smoke is no exception. When burned, cannabis releases chemicals that are harmful to the lungs. In fact, apart from nicotine, cannabis smoke contains similar toxins and carcinogens to cigarette smoke. It has even higher concentrations of some toxins and causes more lung inflammation than tobacco smoke.
It shouldn’t be surprising, then, that smoking cannabis can cause symptoms of bronchitis, such as:
Persistent cough
Increased mucus production (wet cough)
Wheezing (noisy breathing)
Shortness of breath
In addition to symptoms, studies have found direct effects of smoking cannabis on the lungs. Here are some examples:
There are microscopic effects on the lungs that include signs of inflammation and changes in cells that line the airways.
Imaging shows higher rates of airway inflammation and thickening, called bronchiectasis.
Pulmonary (lung) tests find changes in air movement patterns in the lungs that are different from those of tobacco smokers.
Does smoking cannabis cause lung cancer or lasting lung damage?
Smoking cannabis does have some long-term effects. And researchers are just beginning to uncover what they mean.
For a long time, it has been difficult to determine the long-term effects of cannabis use. This is partly because about 70% of people who smoke cannabis also smoke tobacco. Smoking cigarettes causes chronic lung diseases and cancer. So, this overlap makes it hard to separate the harmful effects of tobacco from the effects of smoking cannabis.
Additionally, there are many different methods of smoking cannabis. And this changes the effect of the inhaled smoke on the lungs. This may make it difficult to spot patterns of cause and effect in the research. Plus, many lung conditions take a long time to develop, requiring long-term studies.
All that said, let’s take a look at what the research shows.
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Does smoking cannabis cause asthma?
It’s possible. A study of electronic health records for thousands of regular cannabis smokers found that cannabis smokers were more likely to have asthma than non-cannabis smokers. This link was there whether or not they also smoked tobacco cigarettes. A similar study in Norway found the same link. But direct cause-and-effect hasn’t been determined.
It’s clear that cannabis can worsen existing asthma. Overall, people with asthma who smoke cannabis have more frequent asthma attacks and symptoms than people who don’t smoke cannabis.
Confusingly, there’s some evidence that cannabis smoke can work as a bronchodilator. This means it relaxes the airways and may help to ease breathing. But this effect is short-lived and might go away with prolonged cannabis use.
Overall, the risks of smoking outweigh any possible benefit. Experts recommend that people with asthma avoid smoking cannabis or tobacco, as well as secondhand smoke.
Does smoking cannabis cause COPD?
It’s unclear because the evidence is mixed. Some research suggests cannabis smoking increases the risk of chronic obstructive pulmonary disease (COPD) even without tobacco smoking. But other evidence doesn’t show that smoking cannabis leads to COPD.
It’s not clear why this is. It may be because of the absence of nicotine in cannabis smoke, as well as a possible anti-inflammatory effect of tetrahydrocannabinol (THC), the active part of cannabis that can cause a “high” feeling. More research is needed to understand the relationship better.
Does smoking cannabis cause lung cancer?
Research hasn’t found a strong link between pure cannabis smoke and lung cancer.
Smoking cannabis could cause lung cancer because cannabis smoke contains many cancer-causing chemicals. In fact, the lung tissue of regular cannabis smokers has been found to have widespread inflammation and possible signs of precancer. And some studies have found a link between heavy cannabis smoking and lung cancer. Other studies suggest that smoking both tobacco and cannabis increases the risk.
But these studies didn’t prove that smoking cannabis causes lung cancer. Plus, they’ve been criticized for poorly measuring cannabis use and studying very few cannabis-only smokers. And some studies have found no association between smoking cannabis and developing lung cancer.
The current consensus is that there isn’t enough evidence to say smoking cannabis increases the risk of lung cancer. But more research is needed.
Does smoking cannabis cause ‘bong lung’?
Some heavy cannabis smokers develop areas of severe damage in their lungs that cause air pockets. This irreversible form of emphysema (bullous emphysema) can cause severe breathing problems. In theory, it could be due to deep inhalation and breath holding associated with smoking cannabis.
The evidence for the link between so-called “bong lung” and cannabis use is — you guessed it — unclear. There have been multiple case reports in individuals who heavily use cannabis (not only in people who use bongs). But, once again, more research is needed.
Which way of smoking cannabis is most harmful to the lungs?
There are many ways to smoke cannabis. But the bottom line is that no matter how you smoke it, burning cannabis creates toxic chemicals that damage the lungs. The damage can be worse if you’re burning cannabis that contains pesticide residue.
Blunts and spliffs
Blunts and spliffs are common terms for products that combine cannabis with tobacco. Blunts are cigars that have been filled with cannabis and wrapped in tobacco leaves. Spliffs are cigarettes with a blend of tobacco and cannabis.
Smoking cannabis with tobacco is the most harmful way to smoke cannabis. That’s because it:
Exposes you to higher levels of toxic chemicals
Increases the risk of persistent cough, asthma, and COPD
May make THC more habit-forming (according to animal studies)
May increase the risk of developing cannabis use disorder
Could make it more difficult to quit smoking cigarettes
Bongs, pipes, and joints
Bongs, which are water-filled pipes, are commonly used to smoke cannabis. Cannabis is also smoked in dry pipes. Cannabis cigarettes, called joints, contain ground cannabis wrapped in paper.
There’s no evidence that using a bong is safer than other smoking methods. One study found that water pipes reduced THC strength but didn’t reduce the amount of tar found in cannabis smoke. Evidence from tobacco studies also shows that water filtration doesn’t reduce the amount of toxins you inhale.
Is cannabis vapor safer than smoking cannabis?
Cannabis vaporizers offer a different way of inhaling cannabis. They heat herb or oil cannabis into aerosols you can inhale. There are a few different types:
Dried cannabis flower vaporizers
Metered-dose inhalers
E-cigarettes or vape pens
Because they don’t burn the cannabis, vaporizers reduce the amount of toxic chemicals inhaled. This method might also reduce symptoms, like cough and mucus production, associated with smoking cannabis.
Vaporizers and inhalers are often used for medical reasons. E-cigarettes are more commonly available. But they’ve been clearly linked to serious (and sometimes fatal) lung injuries called EVALI (e-cigarette or vaping-associated lung injury).
Most EVALI cases are tied to daily use and a large number of puffs — common behaviors for vape users. E-cigarettes may also contain harmful additives.
Which way of smoking cannabis is least harmful to the lungs?
Smoking cannabis is always damaging to your lungs. Smoking involves the burning of plant material, which creates toxic chemicals that are inhaled into your lungs.
The best way to consume cannabis without exposure to toxic smoke is to stop smoking. Edible and topical cannabis products don’t damage your lungs.
Is smoking cannabis safer than smoking cigarettes?
Cannabis and tobacco cigarettes are the two most commonly smoked substances in the world.
Overall, scientists believe that smoking cannabis has lower risks for lung damage than smoking cigarettes. But this doesn’t mean that it’s safe for a few reasons.
There’s a lot that experts still don’t know about the long-term effects of smoking cannabis. As research continues, this could change.
Historically, cannabis potency has been a lot lower than what it is now. Cannabis is getting stronger, and this could change the outcomes.
Researchers continue to struggle to separate the effects of cannabis from tobacco, in people who use them both.
Frequently asked questions
It depends on the individual. If you have a lung condition like COPD, quitting smoking will certainly help, but it won’t cure your condition. For those without lung disease, research suggests symptoms like coughing and wheezing improve after you stop smoking.
Research hasn’t identified any benefits of smoking cannabis on the lungs.
It might. A recent, large cohort study looked at lifetime cannabis use and mortality (risk of death). It found a link between heavy cannabis use and cardiovascular death in women. There was also an increase in cancer-related death in men who smoked cigarettes.
It depends on the individual. If you have a lung condition like COPD, quitting smoking will certainly help, but it won’t cure your condition. For those without lung disease, research suggests symptoms like coughing and wheezing improve after you stop smoking.
Research hasn’t identified any benefits of smoking cannabis on the lungs.
It might. A recent, large cohort study looked at lifetime cannabis use and mortality (risk of death). It found a link between heavy cannabis use and cardiovascular death in women. There was also an increase in cancer-related death in men who smoked cigarettes.
The bottom line
Smoking cannabis can damage your lungs. It can lead to bronchitis and worsen asthma symptoms in people with asthma. There may be longer-term effects, too, especially when combining tobacco with cannabis. More research is needed to fully understand the impact of cannabis smoking on lung health.
Inhaling a burning substance can never be considered safe. And, if you have lung disease or you’re at risk for lung disease, it’s safest to avoid smoking or vaping anything at all. If you’re consuming cannabis, edibles are much safer for your lungs.
Why trust our experts?
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