CT scans don't lie—cigarettes are harder on the lungs than marijuana
Many have touted smoking marijuana as a safer alternative to cigarettes. New imaging data offer clarity on whether this notion is actually true.
A new analysis in the journal Current Problems in Diagnostic Radiology details a head-to-head comparison of the effects of smoking marijuana versus cigarettes. Using findings from CT scans, researchers laid out how each substance impacts lung health—one more so than the other.
“Perceptions of cannabis smoking and secondhand exposure as safer than tobacco have increased among U.S. adults from 2017 to 2021, despite conflicting scientific evidence,” Mark M. Hammer, MD, with Brigham and Woman’s Hospital, and colleagues note. “It has been suggested that while marijuana may induce bronchitis in current users, but it does not result in permanent airway damage.”
Some studies have linked marijuana inhalation to inflammation of the airway; others have indicated that smoking the drug can lead to emphysema, but overall, other confounding factors have caused researchers to stop short of claiming causation.
One limitation of previous research on the topic is the lack of quantitative assessments that can be deployed to measure differences in lung structure on imaging. The team sought to overcome this by deploying both quantitative and qualitative imaging evaluations of three groups with well-matched controls—one of nonsmokers, one of tobacco-only users, and a third of marijuana-only smokers.
The group retrospectively reviewed medical records to identify subjects who met their criteria and had also undergone a chest CT scan. The scans were used to conduct a quantitative analysis to measure total lung volume (TLV), while a blinded thoracic radiologist examined the scans for the presence of emphysema, centrilobular ground glass opacities, mosaic attenuation, bronchial wall thickening and coronary calcification.
On imaging, the marijuana-only group displayed lower TLV, but significantly fewer instances of emphysema and centrilobular ground glass opacities. Conversely, 62% of the cigarette-only group showed signs of emphysema, while 15% had centrilobular ground glass opacities (compared to just 4% and 2% of marijuana users). What’s more, a significantly larger portion of the cigarette-only cohort also had moderate to severe coronary artery calcifications compared to marijuana users.
“The findings of our study collectively highlight the distinct patterns of pulmonary and cardiovascular manifestations associated with smoking and marijuana use,” the authors note. “It appears that, in general, marijuana users do not ... develop emphysema or pulmonary hyperinflation.”
Although the study’s methodology builds a stronger case for the notion that marijuana causes less lung damage compared to cigarettes, the authors caution that it is worthwhile to dive deeper into users’ history of consumption of both, and whether individuals with a longer history of smoking marijuana might show more signs of pulmonary deterioration over time.
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.