CannaTrials adheres to evidence-based medicine – making statements based on medical evidence.

This page is excerpted and quoted from the National Academies of Science, Engineering, and Medicine.    A Committee of over 40 experts, researchers, and reviewers in The Health and Medicine Division published a 486 page report in 2017 entitled “The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research.
If you would like to access the entire report you may do so by clicking this link.

Medical Marijuana and Chronic Obstructive Pulmonary Disease (COPD)

“COPD is a clinical syndrome that consists of lower airway inflammation and damage that impairs airflow. Ranked as the fourth-leading cause of death worldwide by the World Health Organization, COPD has been estimated to cause more than 3 million deaths worldwide annually and has an estimated global prevalence of 10 percent in adults (Buist et al., 2007; Diaz-Guzman and Mannino, 2014). COPD is diagnosed with spirometry and is defined by a post-bronchodilator forced expiratory volume at 1 second divided by forced vital capacity (FEV1/FVC) <70 percent (fixed cutoff) or as a post-bronchodilator FEV1/FVC below the 5th percentile of a reference population (lower limit of normal). The committee responsible for Marijuana and Medicine: Assessing the Science Base (IOM, 1999) suspected, but did not conclude, that chronic cannabis smoking causes COPD.

It is unclear whether regular cannabis use is associated with the risk of developing COPD or exacerbating COPD. Current studies may be confounded by tobacco smoking and the use of other inhaled drugs as well as by occupational and environmental exposures, and these studies have failed to quantify the effect of daily or near daily cannabis smoking on COPD risk and exacerbation. There is no evidence of physiological or imaging changes consistent with emphysema. The committee’s findings are consistent with those of a recent position statement from the American Thoracic Society Marijuana Workgroup which concluded that there was minimal impairment in light and occasional cannabis smokers when controlled for tobacco use and that the effects in heavy cannabis smokers remain poorly quantified (Douglas et al., 2015). The review by Tashkin (2013) concluded that the lack of evidence between cannabis use and longitudinal lung function decline (Pletcher et al., 2012) argues against the idea that smoking cannabis by itself is a risk factor for the development of COPD. This is further supported by the findings of Kempker et al. (2015), who concluded that smoking cannabis was not associated with lower FEV1 after adjusting for tobacco smoking. However, smoking cannabis was associated with a higher FVC, which may have led to a spuriously lower FEV1/FVC. Therefore, their analyses also do not support an association between heavy cannabis use (>20 lifetime joint-years) and obstruction on spirometry. The position statement by Douglas et al. (2015) concluded that the lack of solid epidemiologic association suggests that regular cannabis smoking may be a less significant risk factor for the development of COPD than tobacco smoking.

Cross-sectional studies are inadequate to establish temporality, and cohort studies of regular or daily cannabis users are a better design to help establish COPD risk over time. Better studies are needed to clearly separate the effects of cannabis smoking from those of tobacco smoking on COPD risk and COPD exacerbations, and better evidence is needed for heavy cannabis users.

7-2(a) There is limited evidence of a statistical association between occasional cannabis smoking and an increased risk of developing chronic obstructive pulmonary disease (COPD) when controlled for tobacco use.
7-2(b) There is insufficient evidence to support or refute a statistical association between cannabis smoking and hospital admissions for COPD.


[1] The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research | The National Academies Press. 2017. Pages 186-189. Download the complete 486 page report.

**Important Note:  On many of the health conditions studied by NAS, there was no conclusive evidence of cannabis effectiveness from the study results they reviewed.  The authors included a long section on “research gaps.

It is the Vision and Mission of CannaTrials to fill in some of these research gaps with cannabis clinical trials using specific medical marijuana formulations and testing them in a research protocol with local patients, physicians, processors and dispensaries.  If you are interested in participating in a clinical trial, and helping improve scientific knowledge about health effects of cannabis, please click one of the buttons below on this page.

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