According to recent research on the affects of marijuana smoke, there was documented yet poor-quality evidence that frequent marijuana users had more respiratory symptoms such as cough, sputum production, and wheezing.

Researchers concluded that there was low-strength evidence linking marijuana smoking with the respiratory symptoms in the more than 20 studies included in the analysis and insufficient evidence to link daily marijuana use to changes in pulmonary function or development of obstructive lung disease.

The study highlights the limitations of previous research examining marijuana use and pulmonary outcomes, including the lack of standardized use assessment tools and well-defined study designs with robust assessment and adequate follow-up.

Researchers noted that smoke from burning marijuana contains many of the same toxic gases, particulates and polycyclic aromatic hydrocarbons as cigarette smoke.