Smoking marijuana could do more harm to a person’s lungs than some believe, according to a preliminary study from Canada.
The small study is published in Radiology, a journal of the Radiological Society of North America.
The study says that “global consumption of marijuana is increasing, but there is a paucity of evidence concerning associated lung imaging findings.”
The study looked at existing chest CT images of tobacco smokers, those who smoke marijuana and nonsmokers to look at lung conditions. And they found lungs were less healthy in marijuana smokers than in those who only smoked tobacco.
A particular type of emphysema, paraseptal, was greater among marijuana smokers. In paraseptal emphysema, the little air sacs that take in oxygen and remove carbon dioxide are riddled with small holes that prevent a healthy gas exchange.
Lead study author Dr. Giselle Revah, assistant professor in the department of radiology at the University of Ottawa in Ontario, told NBC News that could be caused because joints aren’t filtered and cigarettes are — and because marijuana smokers inhale differently than cigarette smokers do.
Who they studied
The researchers compared scans from 56 people who smoked marijuana and tobacco with the scans of 33 long-term, heavy tobacco smokers. The study controls were 57 nonsmokers who did not have lung disease or a history of chemotherapy.
“Airway inflammation and emphysema were more common in marijuana smokers than in nonsmokers and tobacco-only smokers,” the study authors wrote. But they added a caveat to the finding, in that some of the marijuana smokers also smoked cigarettes, so it was hard to sort out the impact of the marijuana clearly in those cases,
Additionally, they found that “emphysema rates were higher in age-matched marijuana smokers,” at 75%, than in tobacco-only smokers, at 67%. They didn't find any difference in the rate of coronary artery calcification between age-matched marijuana smokers and tobacco-only smokers.”
Per CNN, “A difference of 8 percentage points between weed plus tobacco and tobacco-only smokers may not seem like a huge difference, but it was significant,” said Revah.
“It suggests that marijuana has additional effects on the lungs than tobacco alone,” Revah told CNN. “Is it the combination of the marijuana and tobacco that makes more holes in the lungs and airway inflammation or just the marijuana itself?”
She also noted that many of the marijuana smokers were well below age 50.
“These patients presumably had less lifetime exposure to smoke, except they’re even sicker than those who are heavy tobacco smokers and have been doing it longer,” Revah said. “We just don’t know if it’s a synergistic effect between the marijuana and the tobacco versus the marijuana alone.”
Other studies raise questions
The researchers said larger studies are needed to confirm and clarify the findings.
But other research seems also to suggest that marijuana smoking is bad for the lungs. A study published in 2021 in the Journal of Adolescent Health found that adolescents age 12-17 who vaped cannabis were twice as likely to experience “wheezing or whistling” in their chests compared to those who used cigarettes or e-cigarettes.
And in June, the journal BMJ Open Respiratory Research published findings that all-cause emergency department visits or hospitalization was “significantly greater among cannabis users than among control individuals. Therefore, cannabis use is associated with increased risk for serious adverse health events and its recreational consumption is not benign.”