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

The takeaway

Despite sharing toxic compounds with tobacco smoke, the epidemiological evidence linking cannabis smoking to lung cancer is inconsistent, though chronic use clearly causes bronchitis-like symptoms and impairs immune function in the lungs.

Cannabis consumers concerned about lung health, pulmonologists, public health professionals, and harm reduction advocates.

What the researchers found

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.

Why it matters

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 numbers in context

Cannabis smoke contains polycyclic aromatic hydrocarbons and volatile organic compounds. Respiratory symptoms resemble chronic bronchitis but may resolve upon cessation. No consistent emphysema finding unlike tobacco.

How the study worked

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

What this study cannot tell us

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.

How to read the evidence

Comprehensive narrative review of an extensive literature, though the underlying evidence base is limited by methodological challenges in cannabis exposure measurement.

When this study was published

2025 publication.

The bigger picture

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.

Questions still open

Do the anti-tumor properties of cannabinoids meaningfully offset combustion-related cancer risk in real-world cannabis smokers?
How do different consumption methods (vaping, edibles) change the respiratory risk profile?

Common questions

Does cannabis cause lung cancer?

The evidence is surprisingly mixed. Cannabis smoke contains many of the same carcinogens as tobacco, but epidemiological studies have not consistently found increased lung cancer risk. Some show increased risk with heavy use or tobacco co-use, while others find no association.

Is vaping cannabis safer for the lungs?

The review advocates for non-combustible methods as harm reduction. While vaping avoids combustion byproducts, it carries its own risks including EVALI (e-cigarette/vaping-associated lung injury) particularly with unregulated products.

Read the original research

Cannabis use and its impact on respiratory physiology and lung cancer risk: Mechanistic and epidemiological insights (Review).

Biomedical reports, 23(5), 180

View on PubMed ↗Publisher’s paper ↗

Citation

Georgakopoulou, Vasiliki Epameinondas; Andreikos, Dimitrios A; Zhu, Wei; Spandidos, Demetrios A. (2025). Cannabis use and its impact on respiratory physiology and lung cancer risk: Mechanistic and epidemiological insights (Review).. Biomedical reports, 23(5), 180. https://doi.org/10.3892/br.2025.2058