Go ahead and draw deep. According to an article in the January 11th issue of the Journal of the American Medical Association (JAMA), occasional cannabis smokers, defined as those smoking less than 20 joints per month, actually enjoy slightly increased lung function in some areas. The study which followed over 5000 men and women over 20 years however noted “an accelerated decline in pulmonary function with heavy use.” (See NPR for more.)

Articles on this are peppering the web. SF Gate’s article sums them up best,

“No one would ever claim that drinking water has the same effect as drinking vodka, even though they’re both liquids and you’re ingesting them the same way. But for some reason we have assumed that because we know the negative outcomes with cigarettes, inhaling any plant material is going to have the same outcomes,” said Amanda Reiman, a UC Berkeley lecturer and director of research at the Berkeley Patients Group, a medical marijuana dispensary.

“This study is challenging the preconceived notions we’ve had for some time about the dangers of smoking cannabis and the similarities to smoking tobacco,” she said

Read more at sfgate.com.