London, United Kingdom: Cannabis smoke exposure, even long-term, is not positively associated with chronic obstructive pulmonary disease (COPD), lung cancer, or irreversible airway damage, according to a literature review published in the journal Breathe.

British researchers reviewed nearly 20 observational studies assessing cannabis inhalation and lung health, involving over 25,000 subjects.

Investigators reported that the available literature fails to support an association between cannabis smoke exposure and the onset of COPD, emphysema, lung cancer, shortness of breath, or irreversible airway damage. “The long-term respiratory effects of cannabis differ from traditional smoking,” authors concluded. “[C]annabis smoking does not appear to be carcinogenic.”

Researchers did identify a link between marijuana inhalation and more frequent cough, sputum production, wheezing, and chronic bronchitis – though they acknowledged that these symptoms largely cease upon quitting. Authors also acknowledged that vaporizing cannabis – a process which activates cannabinoids, but does not heat them to the point of combustion – reduces many of these symptoms.

The study’s findings are similar to those of others reporting that cannabis smoke and tobacco smoke differ significantly in their health effects, and that long-term marijuana smoke exposure is not associated with poor lung health.

For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Marijuana and the lung: hysteria or cause for concern?”, appears in Breathe. See the NORML fact-sheet, “Cannabis Exposure and Lung Health.”

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