Does smoking cannabis damage the lungs?

Smoking cannabis causes respiratory harm, though the pattern differs from tobacco. Regular cannabis smokers have higher rates of chronic bronchitis, increased respiratory symptoms (cough, wheeze, phlegm), and airway inflammation. However, unlike tobacco, cannabis smoking has not been consistently linked to COPD or lung cancer in epidemiological studies — possibly because cannabis users typically smoke fewer cigarettes per day than tobacco smokers. The carcinogen exposure per joint is higher than per cigarette, but total exposure is lower. Vaporization substantially reduces respiratory harm by eliminating combustion byproducts. A 2012 JAMA study found that moderate cannabis smoking (up to one joint per day for 7 years) was not associated with adverse lung function. Heavy use (>20 joint-years) was associated with decreased FEV1. Edibles and tinctures carry no respiratory risk.