A new study published in the journal Radiology shows that those who smoke cannabis, which is the second most smoked substance after tobacco, are more likely to develop emphysema than those who smoke tobacco. Cannabis smokers, according to the study, were also more likely to have higher rates of airway inflammation.
Mucus buildup in the airways, bronchial wall thickening, and irreversible enlargement of the airways were also seen as symptoms in cannabis smokers. And though it’s already known, men who smoke marijuana also have higher rates of gynecomastia (increased breast tissue growth).
In a case-control study, scientists looked at chest CT scans from October 2005 to July 2020 in marijuana smokers, nonsmoker control patients, and tobacco-only smokers. They then compared rates of emphysema, airway changes, gynecomastia, and coronary artery calcification.
In the study, 146 participants were observed, 56 of whom smoked cannabis, 57 were nonsmoker control patients, and 33 were tobacco-only smokers. The researchers found that those who smoke cannabis had higher rates of airway changes than those who smoke cigarettes, or those who don’t smoke at all.
“93% of the marijuana smokers had emphysema rather than 67% of the tobacco-only smokers,” said Doctor Giselle Revah, the lead author of the study and a cardiothoracic radiologist at Ottawa Hospital in Canada, as well as an assistant professor in the department of radiology, radiation oncology and medical physics at the University of Ottawa.
“This can lead to more congestive symptoms and predisposition to infections,” Revah noted. “Ultimately, we need more robust research before we can make sweeping conclusions.”
Researchers suggest that because marijuana is unfiltered, this may be contributing to lung damage.
“When marijuana is inhaled, more particulates reach the airways and are deposited,” Revah explained. These particulates are likely airway irritants. The way marijuana is inhaled compared to tobacco with longer breath hold [and] higher puff volume may lead to microtrauma to the airspaces causing little holes (emphysema).”
Revah adds that other forms of cannabis, such as edibles, lotions or oils, will most likely not have the same effect on users as inhaling smoke.
“The problems that we identified in our study were airway problems (from smoke inhalation),” the lead author said. “It would suggest that vaping, smoking, and pipes may cause these problems. Other forms of [cannabis]: eating, lotions are unlikely to affect the airways — but ultimately, more research is still needed.”
Since its legalization, the use of marijuana has increased across the United States. Maine was one of nine states to legalize marijuana since Colorado and Washington first approved the initiative to legalize the drug in 2012. After Maine legalized marijuana in 2016, use grew from about 12% between 2003 and 2009 to almost 24% in 2018.