However, the marijuana and lung cancer link is still not absolute.
As Dr. Reena Mehra of Case Western Reserve University pointed out, more than 40 percent of Americans 12 years old and older have tried marijuana at least once.
Mehra and her colleagues wrote in the Archives of Internal Medicine, "given the widespread use of marijuana, its use for what are believed to be medicinal purposes, and the increasing abuse and dependence on this substance, it is important to examine potential adverse clinical consequences."
Even with all of the studies that they examined, none of them showed that smoking marijuana leads to lung cancer.
Mehra said, "we must conclude that no convincing evidence exists for an association between marijuana smoking and lung cancer based on existing data."
They did suggest that smoking marijuana could indeed raise the risk of lung cancer because people tend to inhale more deeply and hold the smoke in their lungs longer than cigarette smokers do.
