Increasing rates of marijuana consumption highlights a need for research on the effects of smoking marijuana on the lungs.
Despite, marijuana being the most commonly smoked substance after tobacco and increasing rates of marijuana consumption have shown higher rates in respiratory related diseases, the extent of marijuana’s effect on the lungs are not well known.
A recent retrospective case-control study from the department of radiology, Ottawa Hospital General Campus, published in Radiology, found that marijuana smokers had higher rates of emphysema and airway inflammation changes than non-smokers and tobacco-only smokers.
“I can tell if someone is a heavy or a long-time cigarette smoker when I look at a CT scan,” Giselle Revah, MD, FRCPC, a radiologist at The Ottawa Hospital, where the research was conducted, said in a press release. “With marijuana being the second most inhaled substance after tobacco, I started wondering: What does marijuana inhalation look like on a CT scan? Would I be able to tell if someone was a marijuana smoker, is it different from cigarette smoke?”
Using chest CT examinations from October 2005 to July 2020, the investigators of this study compared rates of emphysema, air way changes, gynecomastia, and coronary artery calcification among a total of 56 marijuana smokers, 57 non-smokers, and 33 tobacco-only smokers. Age- and sex-matched subgroups were created for comparison in tobacco-only smokers older than 50 years.
Higher rates of emphysema were found in marijuana smokers (42 of 56 [76%]) than non-smokers (three of 57 [5%]) (P > .001), but not in tobacco-only smokers (22 of 33 [67%]) (P = .40). Emphysema rates were higher in aged-matched marijuana smokers (28 of 30 [93%]) than in tobacco-only smokers (22 of 33 [67%]) (P = .009).
Rates of airway changes, including bronchial thickening, bronchiectasis, and mucoid impaction were higher in marijuana smokers compared to other groups (P > .001 to P = .04). An age-matched subgroup analysis also showed higher rates of airway changes for marijuana smokers than tobacco-only smokers (P < .001 to P = .006).
Gynecomastia rates were also higher in marijuana smokers (13 of 34 [38%]) than in control patients (5 of 32 [16%]; P = .039), and in tobacco-only smokers (2 of 18 [11%]; P = .040).
There was no difference in coronary artery calcification rates among age-matched marijuana smokers (21 of 30 [70%] and tobacco-only smokers (28 of 33 [85%]) (P = .16).
The investigators suggest these findings may be related to the methods of inhalation that is different and uses longer held breath than tobacco smokers.
Furthermore, the investigators acknowledge certain limitations to their research, such as the small population sample size, its retrospective nature, and inconsistent quantification in the amount of marijuana use, due to its history of being an illegal possession.
Additionally, most marijuana smokers are also tobacco smokers, making it challenging to evaluate the effects of both marijuana and tobacco.
“We've identified an association between marijuana smoking and damage to both the small and the large airways,” Revah said. “We still need more research before we can affect policy change. We need larger, more robust prospective studies with more patients to confirm it.”
Murtha L, Sathiadoss P, Salameh J-P, Mcinnes MD, Revah G. Chest CT findings in marijuana smokers. Radiology. Published online November 15, 2022. doi:10.1148/radiol.212611