Research on the effects of smoking cannabis (marijuana) and any effects on the lungs continue to show that it does not have the detrimental effects so common from cigarette smoking.
Chronic obstructive pulmonary disease is a severe health challenge, and can be evaluated by testing how hard a person can expel air from their lungs, called functional expiratory volume.
This study evaluated 131 heavy marijuana smokers, 112 smokers of marijuana plus tobacco, 65 tobacco smokers, and 86 non-smokers. The authors found that marijuana smokers had lungs just as healthy as non-smokers, while the cigarette smokers showed damaging changes to lung function. Those who smoked both did not have damage beyond that found with tobacco alone.