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Experts say the way marijuana smoke is inhaled may contribute to its higher risk of lung ailments. Manon Allard/Getty Images
  • Researchers say emphysema and airway inflammation is more common in marijuana smokers than it is people who smoke tobacco.
  • Both tobacco and marijuana smokers also have significantly higher rates of lung ailments than people who don’t use either substance.
  • Experts say the way marijuana is inhaled may contribute to the higher risk of lung ailments.

Marijuana may be more harmful to the lungs than tobacco when it comes to the frequency of emphysema and airway inflammation.

That’s according to a new study published today in Radiology, a journal of the Radiological Society of North America.

Researchers said the difference may come down to marijuana smoke entering the lungs unfiltered and that users tend to hold inhalations longer to glean the psychoactive effects.

More is being discovered about marijuana as it becomes legal recreationally in recent years in more U.S. states and Canada.

The study’s authors say marijuana is one of the most widely used psychoactive substances in the world and the most commonly smoked substance after tobacco.

“We know what cigarettes do to the lungs,” said Dr. Giselle Revah, a study author and a cardiothoracic radiologist and assistant professor at the University of Ottawa in Canada, in a statement. “There are well-researched and established findings of cigarette smoking on the lungs. Marijuana we know very little about.”

Revah and her team compared the results of chest CT scans from 56 marijuana smokers with those of 57 non-smokers and 33 tobacco-only smokers.

Of the marijuana smokers, 75% had emphysema, a lung disease causing breathing difficulty, compared to 67% of the tobacco-only smokers. Only 5% of the non-smokers had emphysema.

Paraseptal emphysema, which damages tiny ducts connected to the air sacs in the lungs, was the predominant subtype of emphysema in marijuana smokers compared to the tobacco-only group.

Airway inflammation was also more common in marijuana smokers than the non-smokers and tobacco-only smokers, as was gynecomastia (enlarged male breast tissue due to a hormone imbalance).

Gynecomastia was discovered in 38% of marijuana smokers, compared to 11% of tobacco-only smokers and 16% of non-smokers.

Researchers also found similar results among subgroups of the same age range, where emphysema and airway inflammation rates were also higher in marijuana smokers than tobacco-only smokers.

There was no difference in coronary artery calcification between age-matched marijuana and tobacco-only groups.

Dr. Shahryar Yadegar, a pulmonologist and medical director of the ICU at Providence Cedars-Sinai Tarzana Medical Center in California, told Healthline the research may help confirm a trend doctors are seeing in younger people showing more breathing difficulties.

“Any type of inhalation of particulate matter, whether tobacco smoke or marijuana, causes inflammation within the airways,” Yadegar said. “However, the additives in both, including flavors, preservatives, and pesticides, can be highly variable between cannabis and tobacco products.”

“Patients suffering from chronic conditions sometimes try cannabis-derived products for pain relief and management,” Yadegar added. “Some patients have luck with applying cannabis-derived products topically or ingesting, and these do not have the same implications as inhaled products. It is an individualized approach and may require trial and error.”

Jordyn Mastrodomenico is the clinical director at ChoicePoint, a New Jersey-based addiction treatment center. She told Healthline the question of which is worse for the lungs – marijuana or cigarettes, is complex and depends on many factors.

“What’s interesting to note here is that weed damages the lungs owing to the way it’s smoked,” Mastrodomenico said. “Marijuana is inhaled much more deeply with the breath held for a longer time. This increases the length of exposure of alveoli to irritants.”

Mastrodomenico noted that, with a deeper breath, users allow a greater chance for chemicals to reach deeply into the airway tract.

“When exhaled, it’s difficult for lungs to clear the high amount of irritants hence the residual volume is high with pollutants,” she explained. “Another significant point being (that) marijuana smoke contains more carcinogens, about 50 percent more benzopyrene, and 75 percent more benzanthracene and more phenols, vinyl chlorides, nitrosamines, reactive oxygen species, than tobacco.

“High content and the way it’s typically smoked, marijuana contributes to four times (the amount of) tar deposition as compared to cigarette smoking,” she added.

Revah said in a statement the study’s results were surprising, especially considering the extensive smoking history of the people in the tobacco-only group.

“The fact that our marijuana smokers — some of whom also smoked tobacco — had additional findings of airway inflammation/chronic bronchitis suggests that marijuana has additional synergistic effects on the lungs above tobacco,” she said.

“In addition, our results were still significant when we compared the non-age-matched groups, including younger patients who smoked marijuana and who presumably had less lifetime exposure to cigarette smoke,” Revah added.

Revah said more research is needed, with larger groups of people and more data on how much and how often people smoke. Future research could also look at the impact of different inhalation techniques, such as through a bong, a joint, or a pipe.

“It would be interesting to see if the inhalation method makes a difference,” Revah said.