Marijuana May Prime Lungs for Damage From Tobacco
If you smoke tobacco, and have a history of smoking marijuana, you may have more than double the risk of developing COPD. Findings from a new study suggest that marijuana contributes to lung damage because it may prime the lungs, making them more vulnerable to damage from tobacco. The combination of smoking marijuana and tobacco is found to increase respiratory symptoms and triple the risk of COPD.
According to the study from multiple research centers, published in CMAJ, marijuana and tobacco combined seem to have a synergistic effect on the lungs that increases respiratory symptoms leading to COPD.
Dr. Wan Tan of the University of British Columbia and St. Paul's Hospital and coauthors explains, "This effect suggests that smoking marijuana (at least in relatively low doses) may act as a primer, or sensitizer, in the airways to amplify the adverse effects of tobacco on respiratory health."
The study involved 878 people, age 40 or above, in Vancouver, Canada, using self-reported statistics about marijuana and tobacco use. Smokers were defined as having 365 cigarettes per lifetime, and marijuana use included any history of smoking marijuana. As expected, tobacco use alone increased the risk of COPD. However, smoking marijuana and tobacco increased risk of COPD three- fold, measured by spirometry testing.
The study concluded, “Smoking both tobacco and marijuana synergistically increased the risk of respiratory symptoms and COPD. Smoking only marijuana was not associated with an increased risk of respiratory symptoms or COPD”.
Dr. Donald Tashkin of the University of California Los Angeles (UCLA) wrote in an accompanying editorial, "The findings of Tan and colleagues add to the limited evidence of an association between marijuana use and COPD because their study focuses on an older population (aged 40 or older) that is at greater risk of COPD. Previous studies have failed to find an additive effect of marijuana and tobacco on either chronic respiratory symptoms or abnormal lung function in younger smokers. We can be close to concluding that marijuana smoking by itself does not lead to COPD."
The reasons that smoking both tobacco and marijuana increase COPD risk remain unclear. Dr. Wan Tan suggest that more studies are needed to determine if smoking marijuana alone leads to COPD.