lung disease

Pulmonary emphysema in (A, B) marijuana and (C, D) tobacco smokers. (A) Axial and (B) coronal CT images in a 44-year-old male marijuana smoker show paraseptal emphysema (arrowheads) in bilateral upper lobes. (C) Axial and (D) coronal CT images in a 66-year-old female tobacco smoker with centrilobular emphysema represented by areas of centrilobular lucency (arrowheads). (CREDIT: Radiological Society of North America)

OAK BROOK, Ill. – Emphysema, a deadly disease that causes breathlessness in sufferers, is more common among marijuana users in comparison to cigarette smokers, a new study reveals.

Researchers with the Radiological Society of North America say marijuana users are more likely to develop emphysema because the smoke enters the lungs unfiltered.

“We know what cigarettes do to the lungs,” says study author Dr. Giselle Revah, M.D., a cardiothoracic radiologist and assistant professor at the University of Ottawa, in a media release. “There are well researched and established findings of cigarette smoking on the lungs. Marijuana we know very little about.”

The findings are based on CAT (computed tomography) scans of 56 cannabis smokers, 33 tobacco smokers, and 57 non-smokers. Three-quarters of marijuana users, two-thirds of tobacco users, and five percent of non-smokers developed emphysema.

Airway inflammation was also more common among marijuana smokers than the others, as was enlarged male breast tissue due to a hormone imbalance. The condition, known as gynecomastia, was identified in almost four in 10 marijuana smokers compared with one in nine tobacco smokers and 16 percent of the healthy controls.

Airway changes in a 66-year-old male marijuana and tobacco smoker. Contrast-enhanced (A) axial and (B) coronal CT images show cylindrical bronchiectasis and bronchial wall thickening (arrowheads) in multiple lung lobes bilaterally in a background of paraseptal (arrows) and centrilobular emphysema. (CREDIT: Radiological Society of North America)

Is marijuana doing as much damage as decades of smoking?

The study adds more evidence that marijuana addiction can badly damage the lungs. In some cases, young adults in their 30s are turning up in emergency rooms with a severe, rapid, and advanced form of emphysema. Moreover, they have smoked cannabis for less than a decade but still end up needing long-term oxygen therapy.

The study found paraseptal emphysema was the predominant subtype of the disease in marijuana smokers. It damages tiny ducts that connect air sacs in the lungs.

Marijuana is one of the most widely used psychoactive substances in the world. It is the most-commonly smoked substance after tobacco. Use has increased in recent years amid legalization of recreational marijuana in Canada and several U.S. states.

This policy change has created an urgent need for more information on marijuana’s effects on the lungs, something that is currently lacking. The researchers found similar results among age-matched subgroups, where the rates of emphysema and airway inflammation were again higher in marijuana smokers.

Rates of hardening of the arteries, which can trigger heart attacks and strokes, were the same as cigarette smokers. Dr. Revah says the results are surprising, especially considering the patients in the tobacco-only group had an extensive smoking history.

“The fact that our marijuana smokers—some of whom also smoked tobacco—had additional findings of airway inflammation/chronic bronchitis suggests that marijuana has additional synergistic effects on the lungs above tobacco,” Dr. Revah says. “In addition, our results were still significant when we compared the non-age-matched groups, including younger patients who smoked marijuana and who presumably had less lifetime exposure to cigarette smoke.”

Why is emphysema more prevalent in marijuana users?

Marijuana is smoked unfiltered, while tobacco cigarettes are usually filtered, Dr. Revah explains. This results in more particulates reaching the airways. In addition, marijuana is inhaled with a longer breath hold-and-puff volume than tobacco smoke.

“It has been suggested that smoking a marijuana joint deposits four times more particulates in the lung than an average tobacco cigarette,” Revah adds. “These particulates are likely airway irritants.”

The higher incidence of emphysema may also be due to the way people smoke marijuana. Full inhalation may lead to trauma and changes in peripheral airspace. The team notes that more research is necessary, with larger groups of people and more data on how much and how often people are smoking. Future research will also need to look at the impact of different inhalation techniques, such as through a bong, a joint, or a pipe.

“It would be interesting to see if the inhalation method makes a difference,” Dr. Revah concludes.

Emphysema is a form of COPD (chronic obstructive pulmonary disorder), which affects more than 12.5 million people in the United States, according to the American Lung Association.

The findings are published in the journal Radiology.

South West News Service writer Mark Waghorn contributed to this report.

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