Legalizing Cannabis: A physician's primer on the pulmonary effects of marijuana

Habitual smoking of marijuana is associated with multiple respiratory symptoms such as cough, sputum production, and wheezing .These symptoms are not significantly different from those exhibited by tobacco smokers. Furthermore, endobronchial biopsies of habitual smokers of marijuana and /or tobacco have shown that both marijuana and cigarette smoking cause significant bronchial mucosal histopathology and that these effects are additive. Although marijuana smokers have minimal changes in pulmonary function studies as compared to tobacco smokers, they may develop bullous disease and spontaneous pneumothoraces. The relationship between marijuana smoking and lung cancer remains unclear due to design limitations of the studies published so far. These findings should warn individuals that marijuana smoking may result in serious short-term and long-term respiratory complications, and habitual marijuana use should be viewed with caution. The medical literature so far does not support routine evaluation by pulmonary function tests or imaging studies; until more definitive data is available, we do not recommend the regular use of these tests in the evaluation of habitual marijuana smokers.