Vaporized cannabis did not help breathing or exercise endurance in people with severe COPD | Research

The takeaway

A randomized trial of 16 adults with advanced COPD found that a single dose of vaporized cannabis had no meaningful positive or negative effect on breathlessness, exercise endurance, or lung function.

Read this if you have COPD and are considering cannabis for respiratory symptom relief.

No meaningful difference between cannabis and control on any COPD outcome

What the researchers found

Despite decades-old studies showing that smoked cannabis can act as a bronchodilator in healthy people and those with asthma, this randomized controlled trial found no such benefit in people with advanced COPD.

Sixteen adults with severe COPD (average lung function at 36% of predicted normal) inhaled vaporized cannabis containing 18.2% THC or a control. Researchers then measured their breathlessness during cycling exercise, exercise endurance time, lung function at rest, and various cardiac and metabolic parameters.

Across every outcome measured, there was no clinically meaningful difference between the cannabis and control conditions. Breathlessness ratings during exercise were nearly identical (2.7 versus 2.6 Borg units). Exercise endurance times were similar (3.8 versus 4.2 minutes). Spirometry, impulse oscillometry, cognitive function, psychoactivity, and mood also showed no significant differences.

Why it matters

Some people with COPD use cannabis hoping it will help their breathing, partly based on old studies showing bronchodilatory effects in other populations. This rigorous trial found that those earlier findings do not translate to advanced COPD. The null result is itself important information, as it helps patients and clinicians make informed decisions.

The numbers in context

16 participants with advanced COPD. Mean FEV1: 36% predicted. Cannabis dose: 35 mg at 18.2% THC. Breathlessness at isotime: 2.7 (cannabis) vs 2.6 (control) Borg units. Exercise endurance: 3.8 (cannabis) vs 4.2 (control) minutes. No significant differences in any measured outcome.

How the study worked

This was a randomized controlled trial of 16 adults with advanced COPD (mean FEV1 36% predicted). Participants inhaled 35 mg of vaporized cannabis (18.2% THC, less than 0.99% CBD) or control. Outcomes included breathlessness during cardiopulmonary exercise testing, exercise endurance time, resting lung function (spirometry and impulse oscillometry), cognitive function, psychoactivity, and mood.

What this study cannot tell us

The sample was very small at 16 participants. Only a single dose was tested, and chronic effects might differ. The cannabis used had very low CBD content, and CBD may have different respiratory effects. Only advanced COPD was studied, and results might differ in mild or moderate disease. The study design was acute rather than looking at longer-term outcomes.

How to read the evidence

This is a randomized controlled trial, the gold standard for intervention studies, though the small sample size of 16 limits generalizability.

When this study was published

Published in 2018. This remains one of the few RCTs specifically testing cannabis in COPD.

The bigger picture

This study fills a specific gap in the literature, testing whether the bronchodilatory properties of cannabis observed in healthier populations hold up in advanced lung disease. The negative result suggests that the degree of airway disease in COPD may be too severe for cannabinoid-mediated bronchodilation to provide meaningful benefit, or that different mechanisms are at play in COPD versus asthma.

Questions still open

Would higher CBD content produce different respiratory effects in COPD? Could chronic low-dose cannabinoid use affect COPD symptoms differently than a single acute dose? Do milder stages of COPD respond differently to cannabinoid bronchodilation?

Common questions

Does cannabis help with COPD?

This trial found no benefit from a single dose of vaporized high-THC cannabis in people with severe COPD. Breathing difficulty, exercise tolerance, and lung function were all unchanged compared to control.

But doesn't cannabis open up airways?

Earlier studies found acute bronchodilatory effects in healthy people and those with asthma, but that effect did not translate to advanced COPD in this trial. The severe structural lung damage in COPD may limit any bronchodilatory benefit.

Read the original research

Effect of Vaporized Cannabis on Exertional Breathlessness and Exercise Endurance in Advanced Chronic Obstructive Pulmonary Disease. A Randomized Controlled Trial.

Annals of the American Thoracic Society, 15(10), 1146-1158

View on PubMed ↗Publisher’s paper ↗

Citation

Abdallah, Sara J; Smith, Benjamin M; Ware, Mark A; Moore, Michelle; Li, Pei Zhi; Bourbeau, Jean; Jensen, Dennis. (2018). Effect of Vaporized Cannabis on Exertional Breathlessness and Exercise Endurance in Advanced Chronic Obstructive Pulmonary Disease. A Randomized Controlled Trial.. Annals of the American Thoracic Society, 15(10), 1146-1158. https://doi.org/10.1513/AnnalsATS.201803-198OC