Marijuana, cigarette smokers at increased risk of emphysema

Smoking marijuana in combination with cigarettes may lead to increased damage of the lung's air sacs, according to research being presented today at the annual meeting of the Radiological Society of North America (RSNA).

It is commonly believed that smoking marijuana is not harmful to the lungs. There is an abundance of established research that identifies the harms of cigarette smoking. In contrast, very little is known about the effects of marijuana smoking, and even less research has been done on the combined effects of smoking marijuana and cigarettes.

“Marijuana is the most widely used illicit psychoactive substance in the world, and its use has increased in Canada since the legalization of non-medical marijuana in 2018,” said study co-author Jessie Kang, M.D., cardiothoracic radiologist and assistant professor in the Department of Diagnostic Radiology at Dalhousie University in Halifax, Nova Scotia, Canada. “Currently, not much research exists on the effects of marijuana smoking on the lungs.”

The researchers found that people who combined marijuana and cigarettes were 12 times more likely to have centrilobular emphysema than non-smokers. Centrilobular emphysema is a type of pulmonary emphysema where the air sacs within the lungs are damaged. This can lead to breathing difficulties and other serious respiratory symptoms.

“The mean number of marijuana smoking years was less than compared to cigarette smokers and combined marijuana and cigarette smokers,” Dr. Kang said. “However, marijuana that is smoked is often unfiltered, which can potentially lead to more damaging particles entering the airways and lungs.”

Combined marijuana and cigarette smokers were three to four times more likely to have airway wall thickening, which can lead to infections, scarring and further airway damage. Association with marijuana only and smoking only with bronchial wall thickening was not as significant. Similar results were seen with centrilobular and paraseptal emphysema, suggesting that the combination of cigarette and marijuana smoking may have a synergistic role on the lungs and airways.

Reference: Marijuana, cigarette smokers at increased risk of emphysema, Radiological Society of North America, Meeting: 109th Scientific Assembly and Annual Meeting of the Radiological Society of North America.