New Study Finds Smoking Cannabis Is Not Associated With Lung Cancer Or Irreversible Airway Damage

A recent review of studies assessing cannabis inhalation and lung health has found that exposure to cannabis smoke is not linked to lung cancer, chronic obstructive pulmonary disease (COPD), or irreversible airway damage.

Published this month in the journal Breath, the literature review was conducted by a team of scientists in London and back up previous findings.

They reviewed almost 20 observational studies involving over 25,000 participants and found that even long-term exposure to cannabis smoke is not associated with the main dangers of tobacco smoke exposure, including COPD, emphysema, lung cancer, shortness of breath, or irreversible airway damage.

The scientists did note an association between inhaling cannabis smoke and bronchitis, frequent coughs and wheezing. However, they also acknowledge that these symptoms are not permanent and usually stop upon quitting.

They also pointed out that vaporising cannabis or cannabinoids reduces many of these symptoms.

No increased risk

The researchers said in the review: “Tobacco smoking is well known to increase the risk of chronic bronchitis, emphysema and small airways disease (all components of chronic obstructive pulmonary disease; COPD), as well as the development of various forms of lung cancer.

“It might be expected that chronic cannabis smoking would have similar sequelae considering that the contents and properties of tobacco and cannabis smoke are similar.  However, observational studies tell a different story.

When discussing the deleterious effects of cannabis smoke, the authors noted that: “Respiratory symptoms such as cough, sputum production and wheeze are increased in current cannabis users”

However, those who quit smoking cannabis “show a significant reduction in morning cough, sputum production and wheeze compared to those who continue to smoke. Quitters also had no increased risk for developing chronic bronchitis compared with nonsmokers at follow-up 10 years later.”

Lung cancer and cannabis smoke

Discussing the risks of lung cancer, the researchers said: “The clear association of tobacco smoking and lung cancer and the similar carcinogens present in burning cannabis plant material have long raised the possibility of an association of marijuana use and lung cancer.

“However, as with chronic lung disease, there is currently little evidence of a definite link.”

They go on to say that they do not know why cannabis smoking does not appear to be carcinogenic.

“Various factors might contribute, e.g. potential anti-inflammatory and anti-neoplastic properties of THC and other cannabinoids,” the investigators postulated.