In France, the
lung cancer remains one of the deadliest cancers, and in nearly 80% of cases it is linked to tobacco, according to the National Cancer Institute. Cannabis has become commonplace, sometimes perceived as a gentler drug. Many people wonder if smoking a joint really damages the lungs.
In practice, cannabis is almost always smoked, most often mixed with tobacco in joints, which complicates the issue. The INCa classifies inhaled cannabis among the suspected risk factors for lung cancer, and a European foundation recalls that cannabis, pipes or shisha increase this risk. But the answer depends mainly on how and how much you smoke.
Smoked cannabis and the lungs: why the risk of lung cancer exists
The smoke of cannabis very similar to that of tobacco: we find carbon monoxide, tars, polycyclic aromatic hydrocarbons, nitrosamines or benzopyrene described by La Revue du Praticien. In France, consumers often inhale more deeply and keep the smoke in the lungs longer than a cigarette, which increases the quantity of toxic substances deposited on the bronchi.
For Brooks Udelsman, a thoracic surgeon at the University of Southern California, these particles cause chronic inflammation and DNA damage. He recalls that THC promotes the transformation of certain compounds into even more aggressive molecules. When inflammation and DNA changes last for years, the terrain becomes more favorable for the development of a lung cancer.
Cannabis and lung cancer: what the studies show
Major epidemiological analyzes deliver a nuanced message. In a group of six case-control studies including 2,159 people with lung cancer and 2,985 controls, the International Lung Cancer Consortium did not find a significant overall increased risk among cannabis smokers, but an inconclusive signal for certain adenocarcinomas among the highest users.
A large Swedish cohort of men followed for around forty years observed, in those who had used cannabis more than fifty times, a risk of lung cancer about double compared to the others. On this point, Brooks Udelsman remains cautious: “What we don’t know at the moment is the relationship with dose. So, if someone smokes marijuana occasionally once a week, once a month, or a few times a year, do they still have the same risk?“For this surgeon, the risk seems especially concentrated among daily consumers or several times a day.
Occasional or daily use: when does cannabis cause concern for the lungs?
Studies often speak in joint years: smoking a joint per day for ten years corresponds to ten joint years. Signals of excess risk appear mainly at high levels, while rare use seems to cause mainly transient irritation of the bronchi.
The fact remains that tobacco weighs much more: it alone explains nearly 80% of lung cancers. And when cannabis and tobacco are smoked together, as in most French joints, lung damage and the risk of cancer add up.