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People who smoke both marijuana and cigarettes are 12 times more likely than non-smokers to have emphysema, according to preliminary research being presented this week by a Dalhousie University physician at the annual meeting of the Radiological Society of North America in Chicago.

The finding challenges the belief that smoking marijuana is not harmful to the lungs, while adding to limited information on the effects of marijuana smoking and the combined effects of smoking marijuana and cigarettes.

Dr. Jessie Kang, a cardiothoracic radiologist and assistant professor in Dalhousie's Department of Diagnostic Radiology, examined the chest CT images of four patient groups: non-smokers, cigarette smokers, marijuana smokers and combined marijuana and cigarette smokers. Marijuana smokers included in the study had smoked marijuana at least four times a month for two years.

Preliminary findings suggest that those smoking both marijuana and cigarettes had more emphysema -- a condition where the air sacs in the lungs are damaged -- than non-smokers or those who smoke cigarettes alone. This can lead to breathing difficulties and other serious respiratory symptoms.

Combined marijuana and cigarette smokers were three to four times more likely to have airway wall thickening than non-smokers, which can lead to infections, scarring and further airway damage.

Dr. Kang is available to discuss the early results and how further research is needed to identify the long-term effects of smoking marijuana, which has increased in Canada since the legalization of non-medical marijuana in 2018.

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Media contact:

Alison Auld   
Senior Research Reporter   
Communications, Marketing and Creative Services   
Dalhousie University   
Cell: 1-902-220-0491   
Email: alison.auld@dal.ca