Cannabis smoking causes airway inflammation and bronchitis but surprisingly limited evidence for COPD or emphysema
A review found consistent evidence that cannabis smoking causes large airway inflammation and bronchitis, but unconvincing evidence for COPD-like airflow obstruction, with inconclusive evidence for lung cancer.
Quick Facts
What This Study Found
The review noted that despite cannabis being the most widely used illicit drug, respiratory effects were surprisingly under-researched. Key findings:
Consistent evidence showed cannabis smoking was associated with large airway inflammation, bronchitis symptoms, increased airway resistance, and lung hyperinflation.
However, the evidence that cannabis leads to COPD features (airflow obstruction and emphysema) was "not convincing." While case reports described bullous emphysema in cannabis smokers, systematic studies had not confirmed this association. These cases likely represented uncommon adverse effects in very heavy users.
The assumption that cannabis smoking would have similar effects to tobacco smoking appeared to be incorrect. Cannabis had quite different effects on lung function.
Evidence for respiratory malignancies was described as "controversial" and "inconclusive."
Key Numbers
Consistent findings: large airway inflammation, bronchitis symptoms, increased airway resistance, lung hyperinflation. Not convincing: COPD-like obstruction, emphysema. Inconclusive: lung cancer.
How They Did This
Expert review of observational studies examining the effects of cannabis smoking on respiratory function, including studies of lung function parameters, airway inflammation, and cancer risk.
Why This Research Matters
The finding that cannabis and tobacco have different lung effects challenged assumptions and had implications for harm reduction messaging and clinical assessment of cannabis smokers.
The Bigger Picture
This review helped distinguish cannabis lung effects from tobacco effects, establishing that while cannabis smoking is not harmless to the lungs, it may not carry the same specific risks as tobacco for chronic lung disease.
What This Study Doesn't Tell Us
Inherent difficulty studying an illegal habit. Confounding by concurrent tobacco use in many studies. Limited long-term prospective data. Publication bias toward positive findings.
Questions This Raises
- ?Why does cannabis affect the lungs differently than tobacco?
- ?Would vaporization or oral consumption avoid the respiratory effects of smoked cannabis?
Trust & Context
- Key Stat:
- Cannabis has quite different lung effects than tobacco despite being smoked
- Evidence Grade:
- Expert review synthesizing available evidence with honest assessment of what was convincing versus inconclusive.
- Study Age:
- Published in 2011. Larger longitudinal studies have since provided more data on cannabis and lung function.
- Original Title:
- Effects of smoking cannabis on lung function.
- Published In:
- Expert review of respiratory medicine, 5(4), 537-46; quiz 547 (2011)
- Authors:
- Lee, Marcus H S, Hancox, Robert J(2)
- Database ID:
- RTHC-00501
Evidence Hierarchy
Summarizes existing research on a topic.
What do these levels mean? →Frequently Asked Questions
Does smoking cannabis cause the same lung damage as tobacco?
This review found that cannabis and tobacco have different lung effects. Cannabis consistently caused airway inflammation and bronchitis but the evidence for COPD-like damage was not convincing, unlike tobacco.
Can smoking cannabis cause lung cancer?
The evidence at the time was described as "controversial" and "inconclusive." There was some evidence cannabis could be an occasional cause, but it was difficult to separate from the effects of concurrent tobacco smoking.
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Cite This Study
https://rethinkthc.com/research/RTHC-00501APA
Lee, Marcus H S; Hancox, Robert J. (2011). Effects of smoking cannabis on lung function.. Expert review of respiratory medicine, 5(4), 537-46; quiz 547. https://doi.org/10.1586/ers.11.40
MLA
Lee, Marcus H S, et al. "Effects of smoking cannabis on lung function.." Expert review of respiratory medicine, 2011. https://doi.org/10.1586/ers.11.40
RethinkTHC
RethinkTHC Research Database. "Effects of smoking cannabis on lung function." RTHC-00501. Retrieved from https://rethinkthc.com/research/lee-2011-effects-of-smoking-cannabis
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.