A small study comparing marijuana smokers and smokers found a higher rate of emphysema and airway disease among marijuana smokers. Researchers at the University of Ottawa and The Ottawa Hospital looked at the chest CT scans of 56 cannabis smokers, 57 non-smokers and 33 tobacco smokers. The scans were done between 2005 and 2020. They showed that weed smokers had higher rates of paradiaphragmatic emphysema – a condition that causes shortness of breath due to damage to the air sacs in the lungs. Marijuana smokers also had higher rates of other conditions, including bronchiectasis, bronchial wall thickening, and mucosal impaction. Researchers began looking at smoking’s effects on the lungs and health effects because marijuana was only recently legalized in many countries, including Canada in 2018. Therefore, there was not much time to investigate its effects on a wider population. “I can tell if someone is a heavy or long-term smoker when I look at a CT scan,” said Giselle Reva, a radiologist and assistant professor at the School of Medicine. “With marijuana being the second most inhaled substance after tobacco, I began to wonder: What does inhaling marijuana look like on a CT scan? Could I tell if someone was a weed smoker, is it different from cigarette smoke?’
Not a smoking gun
The findings, published in the journal Radiology, showed that 75 percent of weed smokers had emphysema, compared to 5 percent of nonsmokers and 67 percent of smokers. But the researchers say a more in-depth study is needed and they can’t draw strong conclusions from it, especially because 50 of the 56 weed smokers also smoked tobacco. “What’s unique about this study is that there’s been nothing comparing imaging findings in tobacco smokers to marijuana smokers in the past,” Revah said. “There’s actually a lack of imaging research on marijuana, probably because it’s still illegal in many parts of the world and in many states in the US, so I think we were the first to do a project like this.” “We have found an association between smoking marijuana and damage to both the small and large airways,” he said. “We need larger, more powerful prospective studies with more patients to confirm this.”
