Marijuana is legal for medical or recreational use in several parts of the United States. Researchers continue to investigate whether marijuana can cause or even help treat chronic obstructive pulmonary disease.
Some people use marijuana to relieve chronic pain, and there is growing interest in using marijuana to treat a range of other health issues, including epilepsy and the side effects of cancer treatment.
However, there is also concern that recreational use of marijuana increases a person's risk of developing conditions such as chronic obstructive pulmonary disease (COPD).
In this article, we examine the links researchers have found between marijuana and COPD.
These diseases cause inflammation, which impairs airflow in and out of the lungs, making breathing difficult.
COPD is progressive, meaning that a person's symptoms tend to get worse over time. Cigarette smoking is the most common cause of COPD.
Symptoms of COPD can vary in severity but typically include:
- tightness in the chest
- shortness of breath
- unintentional weight loss
- low oxygen level
According to the American Lung Association, cigarette smoking is the cause of around 85–90 percent of COPD cases.
The link between marijuana use and COPD is less certain, and findings have been mixed.
Any association between the drug and the disease seems to relate to the way a person uses marijuana and how often they use it.
Authors of a 2014 study concluded that smoking small amounts of marijuana probably does not cause significant harm, but that heavy use may obstruct the airways and damage lung tissue.
Marijuana contains various chemical compounds called cannabinoids. Two of best-known cannabinoids are cannabidiol (CBD) and tetrahydrocannabinol (THC). THC is the compound that causes the psychoactive effect, or the "high."
Smoking is a common way to use marijuana, but oils, edibles, and tinctures can also contain CBD and THC. No conclusive research suggests that any of these alternate methods lead to lung damage.
The medical community is unsure whether smoking marijuana increases a person's risk of COPD.
According to the American Thoracic Society, heavy marijuana smoking is likely to cause lung damage, which could increase a person's risk of developing COPD.
Many of the harmful and volatile chemicals in tobacco smoke are also present in marijuana smoke. Regardless of the source, smoke, ash, and heat are harmful to the lungs and can damage their lining. This seems to suggest that marijuana smoke is likely to cause COPD.
Also, the manner of smoking can increase the risk of lung damage. A person usually inhales marijuana smoke more deeply and holds it in the lungs for longer than cigarette smoke.
The risk of developing COPD may also depend on how long a person has been using marijuana.
One case study suggests that long-term marijuana use may lead to airflow obstruction and increase a person's breathing rate, which can affect lung function.
Long-term use may also lead to inflammation and swelling of the bronchial tubes, which can cause symptoms of chronic bronchitis, such as increased mucus production, coughing, and wheezing.
Results of other studies indicate that smoking marijuana in moderation does not cause COPD. Authors of a 2013 review concluded that regular marijuana use may cause a slight increase in airway resistance, which may damage the linings of the lungs and make it harder to breathe.
However, there does not appear to be a definitive link between regularly smoking marijuana and developing COPD.
While smoking marijuana may not cause COPD, it may make symptoms more severe in people who already have the disease.
For example, smoking marijuana can damage the small blood vessels in the airways, which may worsen symptoms such as coughing and increased mucus production.
Smoking marijuana also causes microscopic injury to the large airways, which may make symptoms of chronic bronchitis worse.
Smoking anything, including marijuana, is never a good idea for people with lung disease. But, marijuana in other forms may benefit people with COPD.
No conclusive research indicates that marijuana can treat COPD. Certain factors make performing clinical studies with marijuana difficult. The strength of marijuana can vary greatly, depending on the variety, for example.
Also, research has shown that many people who smoke marijuana also smoke cigarettes, which can make it difficult to isolate the effects of marijuana.
However, some research indicates that marijuana use may increase forced vital capacity (FVC).
FVC is the amount of air that a person can forcefully and quickly exhale after taking a deep breath. Reduced FVC is one sign of COPD.
According to a 2015 review of 19 studies, smoking marijuana may increase FVC, though the reasons remain somewhat unclear.
Some researchers have suggested that CBD and THC may decrease swelling in the lungs and help to open the airways in people with COPD.
It is important to understand that many medications and other treatments for COPD exist and that these do not involve marijuana.
Treatment for COPD often involves bronchodilators and steroids that the U.S. Food and Drug Administration (FDA) have studied and approved. The FDA have not approved marijuana to treat COPD.
Determining whether smoking marijuana can cause COPD or make existing symptoms worse will require more research.
It is also unclear whether using a different form of marijuana can decrease COPD symptoms. Some cannabinoids may help open the airways and reduce inflammation in the lungs.
A person with COPD should avoid smoking any substance, including marijuana, as it will likely worsen respiratory symptoms.
Anyone with COPD who is considering using marijuana in forms such as edibles or oils should talk with a doctor first. Marijuana products contain many chemicals, some of which may be unsafe for people with COPD.
Marijuana is not legal in all U.S. states, and it is still illegal under federal law.