Using marijuana frequently ( once a day for 20 years ) has been shown to have no negative impacts on lung health according to the journal Annals of the American Thoracic Society. The study was conducted at Emory University in Atlanta where they looked at the effects of marijuana smoke on the health of lungs.
Some of the authors also noted that marijuana smoke usage may even have some protective lung effects which is in direct opposition to the effects that tobacco smoke currently have. It stated that “[T]he pattern of marijuana’s effects seems to be distinctly different when compared to that of tobacco use.”
All was not all roses however, the researches did note that cannabis users were more likely to have symptoms of bronchitis. Interestingly enough many of those who vaporize marijuana reported fewer respiratory problems.
At the end of the study the researches stated that “[I]n a large representative sample of US adults, ongoing use of marijuana is associated with increased respiratory symptoms of bronchitis without a significant functional abnormality in spirometry, and cumulative marijuana use under 20 joint-years is not associated with significant effects on lung function.”
The student was the largest ever performed looking at the potential negative effects of long term cannabis usage.
The Journal of the American Medical Association (JAMA) in 2012 also found that consistent marijuana use (a joint a day for 7 years ) was also not linked to any decrease in pulmonary function.
If you’d like to read more of the study you can here.