“Someone like you needs medical marijuana.”
“I don't know. I don't want to mess up my lungs.”
“But you don't have to smoke it. You can eat it, too.”
Hearing stuff like that makes me want to scream. For one thing, when you eat cannabis, it gets processed through the liver, turning the delta-9 THC into 11-hydroxy-THC, giving the patient a completely different (and much more powerful) psychedelic effect—not necessarily something a person would be interested in experiencing on a day-to-day basis. But even more important: Light to moderate cannabis smoking has not been shown to have any lasting negative effects on the lungs.
According to a study conducted by Emory University in 2015, in which the ability to exhale in cannabis smokers (who smoked up to a joint a day) was compared to nonsmokers, “Lifetime marijuana use up to 20 joint-years is not associated with adverse changes in spirometric (exhalation strength) measures of lung health.” A weak exhalation is an important marker in diagnosing lung disease, and finding no statistical difference in exhalation tests between smokers and nonsmokers is huge. It means that despite smoking the equivalent of a joint a day (about the size of an average tobacco cigarette) for a fifth of a century, the tested smokers suffered no decrease in lung functionality.
In fact, according to a 2012 study published in the Journal of the American Medical Association, low to moderate long-term users actually showed increased lung capacity compared to nonsmokers. The data came from a long-term study of risk factors for cardiovascular disease which happened upon a large group of testable cannabis smokers while looking at cigarette smokers.
That being said, those who smoke actual joints (rolled in paper) do report bronchial irritation and excessive coughing. Dr. Donald Tashkin, a professor of medicine at UCLA who has been studying the effects of tobacco and cannabis smoke since 1974, says that smoking regularly (once a day or more) “causes visible and microscopic injury to the large airways that is consistently associated with an increased likelihood of symptoms of chronic bronchitis,” however, those symptoms “subside after cessation of use.” (Just in time for winter. If you regular smokers catch yourselves feeling the ol' croup, take a few days off the smoke and stick to edibles. Anecdotal reports of the side effects from vaporizers seem promising, but have yet to be fully studied.)
But what about those of us who smoke more than a joint per day (don't make me count)? For the most part, the same effects hold true for the heavy smoker, but without the small periods of cessation between doses, they are giving their respiratory system less time to recover from throat inflammation and lung irritation—meaning they're more susceptible to chronic bronchitis. However, again, taking a break has so far proven to effectively derail the problem.
Okay. But cancer.
Here's the bad news: Inhaling burnt plant matter—which will always have carcinogens—is never a good thing. And at least two studies (one published in 2006 by the Robert Wood Johnson Foundation, the other in 2014 by the International Journal of Cancer) have found that smoking cannabis does leave tar behind in the lungs.
Which should be the end of the conversation. Tar in the lungs causes cancer. Right? Well, here's where it gets weird (and where the limits are reached, as far as current scientific understanding goes). The last study I mentioned—which found that cannabis smoke left tar behind—discovered no correlation between smoking cannabis and lung cancer.
“Results from our pooled analyses provide little evidence for an increased risk of lung cancer among habitual or long-term cannabis smokers, although the possibility of potential adverse effect for heavy consumption cannot be excluded.”
And here's the unanswered question: How do heavy cannabis smokers avoid the increased risk of lung cancer that cigarette smokers are affected by, despite having tar introduced into their system? So far, no one really knows but one possible answer can be found in research coming out of Complutense University of Madrid that has shown THC's ability to cause tumors to destroy themselves in animals. That research hasn't carried over to human trials … yet. Meanwhile, a German study from 2011 found that CBD hampers cancer cell migration, meaning that cancer cells are prevented from moving around and infecting other parts of the body.
But before you start dancing and proclaiming cannabis the cure for cancer, keep in mind that this research, while coming from respected agencies and being well documented, is still only a very small amount of the work that needs to be done. Until there's more peer review and repeatable results, we won't be sure.
So, at the moment, smoking cannabis is a bit of a gamble but one with very favorable odds. However, if it still sounds too rich for your blood, dry herb and concentrate vaping are still viable options, too.