Does Regular Marijuana Smoking Lead to COPD?

Effect of Cannabis on Lung Disease Such as Chronic Bronchitis and Emphysema

smoking joint in a hand
Can marijuana use lead to COPD?.

Does regular marijuana use lead to chronic obstructive pulmonary disease (COPD)? With more and more states legalizing either the recreational or medical use of cannabis, and with COPD now being the 3rd leading cause of death in the U.S., this is an important question.

COPD and Cigarette Smoking

Most people who express concern about the possible respiratory effects of smoking marijuana, look to the significance of regular cigarette smoking on lung health.

Together, COPD and lung cancer account for roughly 300,000 deaths yearly in the United States alone, with the greatest risk factor being smoking.

Why is There Concern About Marijuana and Respiratory Health?

There are a few reasons that smoking marijuana has raised concern about lung health.

One  concern is due to the presence of irritants and carcinogens (cancer-causing chemicals) in marijuana smoke which are similar to the harmful chemicals in cigarette smoke. It might seem reasonable to conclude that the consequences of regularly smoking marijuana would be similar. While this makes sense, it's important to look at studies that have evaluated the effect of marijuana smoke on lung health directly.

What Do Studies Tell Us About Lung Health And Marijuana Smoke

Researchers have looked at the effects of marijuana smoke on lung health in more than one way. These include:

Symptoms of COPD and Marijuana Smoking

Respiratory symptoms have been reported in those who smoke marijuana including wheezing, a cough, sputum production, and shortness of breath.

These symptoms are most consistent with the type of COPD known as chronic bronchitis, though symptoms alone do not make a diagnosis. To make a diagnosis of COPD requires showing the presence of irreversible obstruction on pulmonary function tests.

Pulmonary Function Tests and Cannabis Use

When looking at pulmonary function tests, it appears that people who have up to 20 "joint years" of cannabis use do not have a significant change in spirometry tests.

(One joint year would mean that a person smoked 365 marijuana cigarettes daily for one year.)

Those who have a greater history of smoking marijuana (more than 20 joint years) are twice as likely to have a change in the ratio of FEV1/FVC less than 70 percent, but unlike those with obstructive diseases such as COPD, the change is related to an increase in FVC (forced vital capacity) rather than an increase in FEV1 (forced expiratory volume in one second.)

Why cannabis would result in an increase in FVC is uncertain, though other researchers believe it may be related to both the bronchodilation effects and the anti-inflammatory effects of cannabis.

Studies in which people smoke primarily resin cannabis mixed with tobacco, however, have found a reduction in pulmonary function tests.

Lung Biopsy Results and Marijuana Smoking

Biopsy of bronchial walls in people who have smoked both cigarettes and marijuana have shown changes that may precede a diagnosis of COPD.

Diagnoses of Lung Diseases and Cannabis Use

In order to talk about what studies show with respect to COPD and marijuana use further, it's important to define a few terms. Chronic obstructive pulmonary disease (COPD) is an obstructive lung disease and includes:

  • Chronic bronchitis
  • Emphysema
  • Bronchiectasis

In general, studies looking at cannnabis use have found a modestly increased risk of bullous emphysema. Bullae refer to blebs or air pockets that are formed in the lungs due to the breakdown of lung tissue with emphysema. When these blebs "pop" they can result in a spontaneous pneumothorax (collapse of the lung,) a condition which is also more common in those who smoke marijuana.

Studies looking at chronic bronchitis have been mixed. Some studies have found a correlation between the smoking of marijuana and chronic bronchitis independent of the effects of cigarette smoking, but others have found no link between the two.

In general, a link was only seen (when there was a link) for those who use marijuana long term.

One study published in the Canadian Medical Journal, did raise concern, though only for those who smoke. It was revealed that among those 40 and older, smokers were two-and-one-half times more likely than nonsmokers to develop COPD, while combining cigarette smoking and marijuana smoking boosted the odds of developing COPD to three and one-half times the risk than those of non-smokers (of either cigarettes or marijuana). Essentially, this means that adding marijuana to the mix of cigarette smoking increases the chances of developing COPD by one-third. The study concluded, however, that smoking only marijuana was not associated with an increased risk of respiratory symptoms or COPD.

Medical Marijuana and COPD Risk

Many states are now approving medical marijuana, and even the National Cancer Institute comments that this may be helpful for people with cancer, reducing pain and nausea and possibly even helping with cachexia (the direct cause of death in 20 percent of people with cancer.) In other words, it is important to know if the medical use of marijuana could be dangerous. At the current time, based on studies to date, the use of medicinal marijuana is not thought to be harmful to the lungs in low cumulative doses.

Marijuana and Lung Cancer Risk

When looking at the risk of marijuana smoking on COPD, it's important to look at the possible effect of cannabis on lung cancer, especially if we are using the argument that many of the chemicals present in cigarette smoke are present in marijuana smoke, and making a deduction from that point. Surprisingly perhaps, there does not appear to be a very significant risk of lung cancer related to marijuana smoking.

Other Sources of Marijuana and Lung Health

When discussing a volatile topic such as marijuana use and the possible negative effects on the lungs, it's important to point out that, for those who are concerned, there are other methods for using cannabis. "Edibles" or the "drops" used by many cancer patients bypass the lungs, eliminating any potential negative effect due to inhalation. Preparations are available as well which are low in THC, and thought to have little, if any, psychoactive effect.

Bottom Line on Marijuana Smoking and Risk of COPD

The studies on marijuana smoking and lung disease, while not completely free of effects, might be some reassurance for those who smoke marijuana, especially those who do so for medical reasons. That is, as long as you do not smoke cigarettes. Cigarette smoking is by far the strongest risk factor for the development of COPD. In addition, cigarette smoking can lead to a host of medical conditions and is also the cause of several cancers.

It's important to point out, however, that regular marijuana smoking is associated with chronic bronchitis symptoms and large airway inflammation.

Certainly there are additional consequences, both social and economical, especially in regions where cannabis is illegal. On the other hand, as we learn how cannabis may help those who are suffering, especially those with cancer, we need to point out that marijuana isn't the monster it might at first appear to be based on the chemicals contained in marijuana smoke alone.

Sources:

Kempker, J., Honig, E., and G. Martin. The Effects of Marijuana Exposure on Expiratory Airflow. A Study of Adults Who Participated in the U.S. National Health and Nutrition Examination Study. Annals of the American Thoracic Society. 2015. 12(2):135-41.

Lutchmansingh, D., Pawar, L., and D. Savici. Legalizing Cannabis: A Physician’s Primer on the Pulmonary Effects of Marijuana. Current Respiratory Care Reports. 2014. 3(4):200-205.

Martinasek, M., McGrogan, J., and A. Maysonet. A Systematic Review of the Respiratory Effects of Inhalational Marijuana. Respiratory Care. 2016. 61(11):1543-1551.

Riberiro, L., and P. Ind. Effect of Cannabis Smoking on Lung Function and Respiratory Symptoms: A Structured Literature Review. NPJ Primary Care Respiratory Medicine. 2016. 26:16071.

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