Cannabis doesn't damage lungs like tobacco

The Associated Press:

Chicago - Smoking a joint once a week or a bit more apparently doesn't harm the lungs, suggests a 20-year study that bolsters evidence that marijuana doesn't do the kind of damage tobacco does.

The study by researchers at the University of California, San Francisco, and the University of Alabama at Birmingham was released Tuesday by the Journal of the American Medical Association.

The findings echo results in some smaller studies that showed while marijuana contains some of the same toxic chemicals as tobacco, it does not carry the same risks for lung disease.

It's not clear why that is so, but it's possible that the main active ingredient in marijuana, a chemical known as THC, makes the difference. THC causes the "high" that users feel. It also helps fight inflammation and may counteract the effects of more irritating chemicals in the drug, said Dr. Donald Tashkin, a marijuana researcher and an emeritus professor of medicine at the University of California, Los Angeles. Tashkin was not involved in the new study.

Study co-author Dr. Stefan Kertesz said there are other aspects of marijuana that may help explain the results.

The analyses showed pot didn't appear to harm lung function, but cigarettes did. Cigarette smokers' test scores worsened steadily during the study. Smoking marijuana as often as one joint daily for seven years, or one joint weekly for 20 years was not linked with worse scores. Very few study participants smoked more often than that.

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