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Marijuana Smoking Not Linked to Chronic Breathing Problems

20-Year-Long Study Finds No Decline in Lung Function for Occasional Pot Smokers

Marijuana Smoking May Stretch the Lungs continued...

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.

Kertesz says the study should reassure people who smoke the drug for medical reasons.

But he says the study doesn’t mean marijuana is safe. It was narrowly focused on lung function. It didn’t look at other possible dangers like cancer.

“One study about one aspect of [lung] function is simply a small part of the puzzle of figuring out what the impacts of this substance are,” Kertesz says.

Experts agree that the study shouldn’t be a reason for people to light up.

“This is a well-designed, well-described study,” says Jeanette M. Tetrault, MD, an assistant professor of medicine at Yale School of Medicine in New Haven, Conn.  

“The jury is still out about smoking marijuana, especially with heavy smokers and long-term chronic use,” says Tetrault, who has reviewed the health effects of smoking marijuana on the lungs but was not involved in the current study. “There are a lot of studies that are conflicting.”

Advice to Patients

Donald P. Tashkin, MD, medical director of the pulmonary function laboratory at the David Geffen School of Medicine at UCLA, has spent his career studying the health effects of marijuana.

He says this study is helpful because it was relatively large and followed people for a long time, which gives him confidence in the results.

“The main thrust of the paper has confirmed previous results indicating that marijuana in the amounts in which it is customarily smoked does not impair lung function,” he says.

His own study of heavy, habitual marijuana smokers -- people who smoked the equivalent of a joint a day for 50 years --  found no harmful effect on lung function.

But he says none of these studies should be taken as the last word.

Other experts agree.

Barry J. Make, MD, co-director of the COPD program at National Jewish Health in Denver, says it can take years and even decades for the lungs to become so damaged by smoking that it would affect airflow, the measure of lung function used in the study.

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