Most people who have inhaled cannabis (either smoking or vaping) have coughed due to the immediate irritation, which may raise the question: What damage is this doing to my lungs? We know that cigarette smoking is associated with lung cancer and chronic obstructive pulmonary disease (COPD). To what extent does a cannabis user experience similar dangers from cannabis use?
The short answer is that the best evidence suggests that cannabis use is significantly less dangerous than nicotine/tobacco use with respect to cancer and COPD, but that it is not without negative impacts.
Know What We Don’t Know
Any attempt to discuss the health implications of cannabis use should acknowledge just how uncertain medical knowledge can be. Some biological processes and medical outcomes are so common that it’s hard to dispute them (the relationship between smoking tobacco and lung cancer or COPD, for example), but in most cases, the evidence is either unclear or there is little good evidence.
In the case of cannabis, research has been limited for a number of reasons, leading to weak empirical evidence. Governmental hostility to cannabis use has historically created many bureaucratic hurdles to cannabis research. This is especially true in the U.S. Additionally, many cannabis smokers also smoke tobacco, making it more difficult to assess the specific impact of cannabis. Furthermore, because cannabis and cannabis use are illegal, many smokers are unwilling to participate in research.
Not Much Biased Research
A further reason that research has been limited is that there is no big profit-making cannabis industry (or at least there has not historically been one). This is worth mentioning because of what is known about the tobacco and sugar industries: both industries produced misleading reports of the health effects of their products. What is known about the effects of cannabis has not been shaped by potentially misleading research that promotes the health benefits of cannabis. Indeed, if there has been biased research, it is likely research hostile to cannabis use. Lester Grinspoon, for a long time one of the few public sources of cannabis research, explicitly set out to demonstrate the harm caused by cannabis. (Grinspoon found little evidence of harm and became a marijuana advocate himself.) U.S. government research groups, especially the National Institute on Drug Abuse (NIDA), have often been accused of significant bias in their reporting on the effects of cannabis. These factors suggest that current research does not have a bias in favor of cannabis.
Cannabis and Your Lung Health
So what are the effects of cannabis use on lungs, as best we understand them? In considering the impact of cannabis use on the lungs, it’s necessary to separate out the two common delivery methods: are you smoking or vaping? There is a lot more known about smoking than there is about vaping. Vaping has become common only recently, so it is difficult to know about its long-term consequences. Because it does not contain many of the problematic chemicals that are found in smoke, there is reason to believe that vaping will have fewer negative health impacts than smoking, but it will be a while before there is empirical evidence for vaping’s impact.
More is known about smoking, which has long been used for cannabis ingestion. At present, the best evidence suggests that cannabis smoking does not pose a significant cancer or COPD risk, although it does have some negative impacts.
Cannabis and Chemicals
Cannabis smoke contains many of the same chemicals as cigarette smoke, including carbon monoxide, ammonia, formaldehyde, benzene and other chemicals, and many of these chemicals are known to be carcinogens or to have other negative health impacts. Despite the presence of these chemicals, there is no clear evidence of a link between cannabis use and lung cancer; some studies have shown such a link, others have not.
Cannabis has been associated with possible anti-carcinogenic effects, which might explain why cannabis smoke, which contains carcinogens, does not cause cancer. There is a good deal of anecdotal evidence regarding the curative powers of cannabis, but there is no significant medical research that shows such curative properties. There is some laboratory evidence of the anti-cancer effect of cannabis; for example, “One study in mice and rats suggested that cannabinoids may have a protective effect against the development of certain types of tumors.”
The Threat of COPD
With respect to COPD or other serious long-term damage, the evidence is less certain, but there is no clear evidence suggesting that long-term damage does occur. The Centers for Disease Control and Prevention do not mention long-term lung damage on their website page dedicated to the health effects of marijuana. NPR interviewed a number of scientists about medical marijuana, and the general conclusion was that it is “unclear whether the drug increases the risk of developing asthma or chronic obstructive pulmonary disease.” Lack of evidence does not prove the safety of cannabis smoking, but at the same time, it is suggestive: if there was a significant safety issue that affected a large proportion of cannabis smokers, there should be plenty of evidence for it (acknowledging, again, the barriers to doing cannabis research).
Other Non-Cancer Risks
Although cancer may not be a danger for a cannabis smoker, there are some deleterious effects of smoking on the lungs. Smoking cannabis is associated with respiratory difficulties, including cough, excess mucus, and bronchitis, as well as having a negative impact on some respiratory conditions like asthma and cystic fibrosis. According to the Centers for Disease Control and Prevention, these symptoms generally improve on quitting, suggesting that the smoke may have a short-term irritating effect, but does not have a long-term impact.
What We Know
In summary, smoking or vaping cannabis will probably irritate your lungs. If you smoke or vape regularly, you may have chronic irritation leading to phlegm, coughing, or bronchitis, but these symptoms generally go away if you stop. As for the long-term problems associated with cigarette smoking (cancer and COPD) there is little evidence to suggest that cannabis is a great danger.