What inhaled cannabis smoke does to the lungs | Research

The takeaway

Cannabis and tobacco smoke contain similar toxins, and cannabis smokers show similar airway inflammation and symptoms as tobacco smokers, but evidence for progression to COPD and emphysema from cannabis alone remains unclear.

Cannabis smokers, people considering switching consumption methods, and pulmonary researchers.

Higher per-puff tar exposure than tobacco

What the researchers found

Cannabis smoking topography (deeper inhalation, longer breath-holding) results in higher per-puff exposures to tar and gases compared to tobacco. Chronic cough, sputum, wheeze, and airway inflammation are similar between cannabis and tobacco smokers. Cannabis smoke has modest bronchodilator properties but of unclear clinical significance. Alveolar macrophages from cannabis smokers show deficits in cytokine production and antimicrobial activity not seen in tobacco smokers.

Why it matters

With cannabis use increasing, understanding the respiratory profile of smoked cannabis helps inform harm reduction choices, particularly for people who also smoke tobacco.

The numbers in context

No specific pooled numbers. Review synthesized findings across the existing literature on cannabis smoking and respiratory health.

How the study worked

Focused literature review examining respiratory symptoms, lung function, bronchial mucosa changes, alveolar macrophage function, COPD, lung cancer, and pulmonary infection risks.

What this study cannot tell us

Relative paucity of well-controlled studies. Most research is confounded by concurrent tobacco use. Conflicting outcomes across studies prevent firm conclusions.

How to read the evidence

Comprehensive narrative review, but underlying evidence base is limited and frequently confounded.

When this study was published

2019 literature review.

The bigger picture

The immune deficit finding in alveolar macrophages is particularly notable since it suggests a unique vulnerability to lung infections that is not present with tobacco smoking alone.

Questions still open

Does the macrophage deficit increase susceptibility to respiratory infections in cannabis smokers? Would switching to vaporization eliminate these respiratory effects?

Common questions

Is cannabis smoke as harmful as tobacco smoke?

Cannabis and tobacco smoke contain similar carcinogens and toxins, and produce similar airway symptoms. Cannabis smoking actually delivers more tar per puff due to deeper inhalation and longer breath-holding.

Does cannabis smoking cause lung cancer?

This review found the evidence remains inconclusive. While cannabis smoke contains carcinogens, there is not yet clear evidence linking cannabis smoking to lung cancer.

Read the original research

Pulmonary effects of inhaled cannabis smoke.

The American journal of drug and alcohol abuse, 45(6), 596-609

View on PubMed ↗Publisher’s paper ↗

Citation

Tashkin, Donald P; Roth, Michael D. (2019). Pulmonary effects of inhaled cannabis smoke.. The American journal of drug and alcohol abuse, 45(6), 596-609. https://doi.org/10.1080/00952990.2019.1627366