Smoking a single marijuana joint is equivalent to smoking 2.5 to 5 cigarettes in terms of damage to the lungs, largely due to differences in how pot and cigarette users smoke.
The Guardian reported that researchers at the Medical Research Institute of New Zealand found that the deep drags taken by marijuana users, along with their penchant for holding smoke in before exhaling, can cause problems like obstructed airways and hyperinflation of the lungs. The lack of filters on marijuana joints also contributes to lung problems, researchers said.
The study involved 339 adult volunteers divided into four groups: marijuana-only smokers, tobacco-only smokers, marijuana and tobacco smokers, and nonsmokers.
All of the smokers reported coughing and wheezing, but only tobacco smokers exhibited signs of emphysema.
The study was published online in the journal Thorax.