The largest and longest study ever focused on cardiovascular disease risk factors recently found that marijuana does not impair lung function in the doses normally inhaled by the majority of users.

The study, published by the Journal of the American Medical Association, tested the lung function of over 5,000 young adults over the course of 20 years.

Dr. Donald Tashkin, professor of medicine at UCLA and not affiliated with the study, reacted to the results saying that the study was “well conducted” and “essentially confirmatory of the findings from several previous studies that have examined the association between marijuana smoking and lung function.”

In addition, the new research found that low to moderate cannabis users actually showed increased lung capacity compared to non-smokers. However, this improvement was not seen in those smoking more than 20 times a month.

Dr. Mark Pletcher, Associate Professor of Epidemiology and Biostatistics at the University of California and lead author of the study expounded, “The largest epidemiologic (case-control) study of the association between marijuana use and lung cancer failed to demonstrate that marijuana increases the risk of developing lung (or, for that matter, upper airway) cancer.”

This is debatable, though, seeing as a recent, smaller study in New Zealand did claim to find a link, but only in very heavy users.

Why smoking marijuana and smoking tobacco should have such different effects on the lungs is also still a matter of dispute. Tashkin argues that the THC in cannabis smoke has anti-inflammatory and immune suppressing properties, which may prevent lung irritation from developing into more serious issues, as happens frequently with tobacco smoking.

“The THC in marijuana has well-defined anti-tumoral effects that have been shown to inhibit the growth of a variety of cancers in animal models and tissue culture systems,” Tashkin says.

While encouraging, these results are a good reminder to all medical and adult use cannabis users—medicate responsibly and in moderation.