Smoking marijuana might do more damage to lungs than cigarettes, a new study suggests.
The study, published in the peer-reviewed medical journal Radiology, found that marijuana might be linked to an increased risk of emphysema compared with smoking tobacco alone.
The results come as more states legalize the drug and health experts, who increasingly are concerned with its impact on lung health, call for more research.
“It’s no surprise to me,” said Dr. David Kaminsky, a pulmonologist and professor of medicine at the University of Vermont who wasn’t involved with the study. “A burning leaf is a burning leaf ... The lung doesn’t know the difference if it’s tobacco or marijuana.”
With emphysema, the lungs’ air sacs are damaged until eventually they rupture, according to the Mayo Clinic. It can cause a long-term cough, shortness of breath and wheezing, and it’s irreversible once it develops.
The new study looked at chest scans from 56 marijuana smokers, 33 tobacco-only smokers and 57 nonsmokers taken from 2005 to 2020 in Canada. It found that emphysema was more common among marijuana smokers than among those who didn’t smoke at all and more common in marijuana smokers who were 50 and older than those who only smoked tobacco.
The researchers also found that a subtype of emphysema that affects the outermost parts of the lung, called paraseptal emphysema, was more common among marijuana smokers than tobacco-only smokers regardless of age.
The scans showed more instances of airway inflammation among marijuana smokers compared to people who smoked cigarettes only or not at all.
The average quantity of marijuana smoked by participants was about 1.85 grams a day, though fewer than half of the smokers specified their daily use. The study included only tobacco smokers 50 and older who smoked at least one pack a day for 25 years.
Due to the some of the study’s limitations, health experts say it’s difficult to directly compare tobacco and marijuana risks. Fifty of the 56 marijuana smokers also smoked tobacco, and the researchers did not account for the participants’ other health conditions.
Still, experts say the study rings alarm bells and suggests that smoking marijuana isn’t risk-free.
“There’s definitely a concern that we’re going to see another generation of lung disease related to these behaviors,” said Dr. Albert Rizzo, chief medical officer of the American Lung Association.
Research on marijuana and health outcomes have been limited and their results mixed. Some studies have found smoking marijuana might cause lung injury linked to an increased risk of chronic bronchitis but did not find significant changes in lung function over time.
The American Lung Association’s position is that smoking in general is harmful to lung health and that marijuana “has been shown to contain many of the same toxins, irritants and carcinogens as tobacco smoke.”
Marijuana might also be more harmful to the lungs because of how people smoke it, Rizzo said. Users typically inhale it more deeply and hold their breath longer than cigarette smokers do, which could expose them to more toxins per breath.
Still, for some, smoking marijuana also offers health benefits. For example, inhaling cannabis triggers certain chemicals that can help quickly relieve migraine symptoms, said Dr. Jordan Tishler, an instructor of medicine at Harvard Medical School and president of the Association of Cannabinoid Specialists.
“Inhalation is a very important approach to certain medical problems that we would have a hard time addressing” without it, Tishler said. “But inhalation doesn’t mean smoking necessarily.”
While he advises against e-cigarettes and vape pens, which have been associated with a lung injury called EVALI, Tishler said a flower or dry herb vaporizer can heat up dry cannabis without exposing the user to dangerous toxins and heavy metals.
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