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Research Summary

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. 

Comments:

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
*Studies that experimentally administered marijuana and assessed its effects immediately or shortly after (e.g., 15 minutes, 1 hour) administration
**Defined variably across studies

Reference:

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.


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