The Canadian study was published in mid-November in the peer-reviewed journal Radiology.
The research looked at CT examinations that were taken between October 2005 and July 2020 at The Ottawa Hospital and its affiliate hospitals to investigate the effects of smoking marijuana on the lungs.
The researchers grouped chest CT examinations according to marijuana smokers, tobacco-only smokers, and nonsmokers.
The “study suggests that distinct radiologic findings in the lung may be seen in marijuana smokers, including higher rates of paraseptal emphysema and airway inflammatory changes … when compared with nonsmoker control patients and those who only smoke tobacco,” said the authors.
Higher Rates of Emphysema
The study found higher rates of emphysema among marijuana smokers (42 out of 56, 75 percent) than nonsmokers (three out of 57, five percent). Emphysema is a serious lung disease, caused in most cases by smoking damage leading to shortness of breath.
Emphysema was found to be more common among the marijuana smokers (28 out of 30, 93 percent) who were 50 and older than the tobacco-only smokers (22 out of 33, 67 percent ) in the age-matched groups. The tobacco smokers were older, so the researchers created age-matched subgroups.
The researchers included tobacco-smokers 50 and older who smoked one pack a day for 25 years at a minimum. For the marijuana smokers the average quantity they smoked was 0.065 ounces (1.85 grams) per day. However, less than half of this group specified the amount they used.
A subtype of emphysema, called paraseptal emphysema, which affects the outermost parts of the lung, was found to be more common among marijuana smokers than tobacco-only smokers regardless of their age, the study said.
Higher Rates of Airway Inflammation
Markers of airway inflammation were found to be higher in the marijuana smokers group versus nonsmokers and tobacco-only smokers.
For marijuana smokers compared to nonsmokers the rates of airway inflammation were: bronchial thickening (64 percent versus 11 percent), bronchiectasis (23 percent versus four percent), and mucoid impaction (46 percent versus two percent).
Bronchiectasis is a condition where the lung airways become widened, leading to a build-up of mucus that may make the lungs vulnerable to infection.
Mucoid impaction is a condition where the airways become filled with mucous.
For marijuana smokers versus tobacco smokers, the rates of airway inflammation were: bronchial thickening (64 percent versus 42 percent), bronchiectasis (23 percent versus six percent), and mucoid impaction (46 percent versus 15 percent).
Analysis of the age-matched subgroups showed an even more significant difference between the rates of bronchial thickening (83 percent versus 42 percent), bronchiectasis (33 percent versus six percent), and mucoid impaction (67 percent versus 15 percent) in marijuana smokers compared to the tobacco-smokers.
The researchers also looked at non-lung-related parameters one of which was Gynecomastia, a condition that causes enlarged breast tissue in boys and men.
They found it to be significantly more common among marijuana smokers (13 out of 34, 38 percent) than in nonsmokers (five out of 32, 16 percent).
The researchers noted that the small sample size in the study limited their ability to draw strong conclusions.
They also noted that most of the marijuana smokers also smoked tobacco (50 out of 56) and said that the participants’ other health conditions were not accounted for.
The study comes as more states are legalizing the drug.
“There’s a public perception that marijuana is safer than tobacco, and this study raises concern this may not be true,” said study author Giselle Revah, assistant professor in the department of radiology at the University of Ottawa in Ontario, according to CNN.