Marijuana Smoking and Pulmonary Complications
The impact of marijuana smoking on pulmonary function and respiratory complications is not clearly understood. Therefore, researchers conducted a systematic review and summarized the findings of 34 studies.
- Short-term marijuana smoking was associated with improved airway response in 10 of 11 challenge studies.* However, the results of 1 challenge study suggested a reversal of this effect after 1.5 to 2 months of marijuana smoking.
- Longer-term** marijuana smoking was inconsistently associated with airflow obstruction. Results from pulmonary function tests (FEV1, FVC, FEV1/FVC, DLCO) were worse in marijuana smokers than in controls in 8 of 14 studies.
- Longer-term marijuana smoking was associated with an increased risk of various respiratory complications (e.g., cough, sputum production, wheezing, dyspnea, pharyngitis, worsening of asthma symptoms) in 14 of 14 studies.
- The overall quality of studies varied. Many failed to control for tobacco smoking, and none defined a standardized measure of marijuana dose.
Although short-term marijuana exposure may cause bronchodilation, longer-term exposure may obstruct airflow. Physiologic data that can describe the relationship between marijuana smoking and airway hyperreactivity are currently inconclusive. Nonetheless, long-term marijuana smoking appears to increase the risk of respiratory symptoms and complications.Julia H. Arnsten, MD, MPH
**Defined variably across studies
Tetrault JM, Crothers K, Moore BA, et al. Effects of marijuana smoking on pulmonary function and respiratory complications: a systematic review. Arch Intern Med. 2007;167(3):221–228.