Office of Research & Development

Marijuana less harmful than tobacco-at least to lungs

A 20-year study by researchers with VA, Kaiser Permanente, and several universities found that people who occasionally smoke marijuana do not suffer lung damage the same way cigarette smokers do. In fact, their lungs may even benefit slightly. But the researchers warn that heavier marijuana use could be riskier. Stefan Kertesz, MD, the study's senior author and a physician-investigator with VA and the University of Alabama at Birmingham, said, "Marijuana is still an illegal drug, and it has many complicated effects on the human body and human functioning." Kertesz and colleagues used data from the Coronary Artery Risk Development in Young Adults (CARDIA ) study. The effort involved more than 5,000 black and white men and women from Birmingham, Chicago, Minneapolis, and Oakland who were recruited when they were between the ages of 18 and 30 and followed from 1985 to 2006. Over a third of the participants reported using marijuana at some point—similar to what other U.S. studies have found. Tobacco use at any level was found to harm air flow and lung volume, whereas light marijuana use actually had a slight beneficial effect. Even moderate marijuana use—one joint daily for seven years—resulted in no lung damage. Heavier or longer-term marijuana use may in fact harm the lungs, said Kertesz, but the study did not include enough heavy marijuana users to draw that conclusion. (Journal of the American Medical Association, Jan. 11, 2012)