Smoking an occasional marijuana joint isn't bad for your lungs. In fact, lighting up once in a while may increase lung function, according to researchers at University of California, San Francisco.
The UCSF study, released today, looked at the pulmonary functions of 5,000 men and women over a 20 year period. It found that those who smoked marijuana for up to seven "joint-years" had a slight increase in lung capacity. What the heck is a "joint-year"? It's defined as an average of one joint a day for seven years, or about one a week for 49 years.
But that doesn't mean that marijuana smokers have the lung capacity of "The Thing" in Fantasic Four. The change in lung capacity doesn't have much of a functional impact, according lead author and UCSF professor Mark Pletcher. "The amount of lung volume that is extra in marijuana smokers at that level versus non-marijuana smokers is very small."
Pletcher says that small difference in lung capacity may simply be because marijuana smokers are better test takers. "People who smoke marijuana tend to inhale very deeply when they smoke, so that may train them for the actual pulmonary function test -- so they can inhale and exhale more quickly and more deeply."
Pletcher says while that may be good news for medical marijuana users, smoking may still cause coughing, phlegm and even wheezing. And smoking too much marijuana may have a negative affect on the lungs. He said the data suggested that very heavy marijuana use was linked to adverse effects on pulmonary function similar to tobacco use.
"When you get above 10 joint-years of exposure, we saw that the more you smoke, the lower your pulmonary function. But we couldn't really prove it because there weren't a lot of heavy smokers in our sample."