TUESDAY, Jan. 10 (HealthDay News) -- Unlike the cigarette habit, occasional pot smoking does not seem to trigger declines in lung function that could lead to breathing problems, a new 20-year study suggests.
"Tobacco takes you down that road toward breathlessness, but low to moderate levels of marijuana don't," said study co-author Dr. Stefan Kertesz.
But there were limits to the study. For example, the findings do not indicate whether occasional (two or three joints a month) pot smokers face a higher risk of lung diseases such as cancer.
Nevertheless, the research should fuel the ongoing debate over medical marijuana, which critics say is too hazardous to serve as a drug to treat conditions such as pain.
It is clear that marijuana smoke irritates the lungs, causing coughing and sputum production, and addiction to marijuana obviously causes problems, noted Kertesz, an associate professor at the University of Alabama at Birmingham. However, as with alcohol and other drugs, the question of harm becomes more ambiguous when it comes to more occasional users who aren't addicted, he said.
"What about the adults who use three joints of marijuana a month for many years?" he said. "Clarifying that is actually quite difficult."
In the new study, researchers examined the findings of a study, which began in 1985, of more than 5,100 people aged 18-30 from Oakland, Calif.; Chicago; Minneapolis; and Birmingham, Ala. Every few years over two decades, the participants took lung tests that measured their lung function through their ability to blow hard into a tube.
The typical tobacco user smoked eight to nine cigarettes a day, while the marijuana users in the study smoked about two to three times over the past 30 days. "That's really different from ['pothead' film icons] Cheech and Chong," he said. "Americans who smoke marijuana typically don't smoke it every day."
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