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Lung Disease & Respiratory Health Center

Marijuana Smoking Not Linked to Chronic Breathing Problems

20-Year-Long Study Finds No Decline in Lung Function for Occasional Pot Smokers
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'These Are Not the Cheech and Chongs of the World'

A healthy adult man can blow out about a gallon of air in one second, says researcher Stefan Kertesz, MD, an assistant professor of medicine at the University of Alabama at Birmingham.

Pot smokers, on average, were able to blow out that gallon of air plus about 50 milliliters.

“That’s roughly one-sixth of a size of a can of soda,” Kertesz says. “It’s not anything anybody would notice.”

The results do have to be put into the proper context, though.

Most marijuana users in the study were light smokers. “These are not the Cheech and Chongs of the world,” Kertesz says.

The average number of times a person using marijuana in the study said they lit up was two to three times per month.

But even in regular users, researchers say they still saw no evidence of breathing problems.

In fact, researchers estimated that lung capacity would stay slightly elevated even if a person had smoked as much as a joint a day for seven years, or two to three joints a day for three years.

The study is published in the Journal of the American Medical Association.

Marijuana Smoking May Stretch the Lungs

But researchers are quick to say that the small improvement seen in this study may have more to do with the way people smoke marijuana -- by taking and holding deep breaths -- than it does with any actual benefit of the drug.

And although they didn’t find any long-term breathing problems associated with occasional pot smoking, it has been linked to some short-term irritation.

“Marijuana does irritate airways, and certainly anyone who’s heard someone cough after smoking marijuana knows that,” says Kertesz. “Is this actually a real benefit to lung health? Probably not.”

What’s more, there was some evidence that very heavy users -- those who smoked the equivalent of a joint a day for 40 years or lit up more than 25 times a month -- might lose lung function.

But because the number of heavy users in the study was small, researchers say they aren’t sure whether those trends are valid or not.

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