Cannabis smoking harms the lungs but its link to lung cancer remains surprisingly unclear

Cannabis smoke contains carcinogenic compounds similar to tobacco, and chronic smoking causes cough, sputum, and wheezing resembling chronic bronchitis. However, epidemiological studies on lung cancer risk show conflicting results. Cannabis impairs alveolar macrophage function but does not consistently cause emphysema. Symptoms often resolve with cessation.

Narrative review synthesizing epidemiological and mechanistic evidence on cannabis smoking's respiratory and oncological effects, including comparison with tobacco smoke exposure.

With cannabis use rising globally, understanding its respiratory effects is critical for public health messaging. The disconnect between cannabis smoke's carcinogenic content and the lack of consistent lung cancer evidence is a puzzle that has practical implications for harm reduction.

The potential anti-tumor properties of THC and CBD observed in lab studies may partly counteract the carcinogenic effects of combustion, creating a complex risk profile that differs fundamentally from tobacco. However, relying on this uncertainty is not a safe assumption.

Narrative review with selective evidence synthesis. Most cannabis-lung cancer studies have methodological limitations including small samples, confounding tobacco use, and difficulty quantifying cannabis exposure. Few long-term prospective studies exist.