Marijuana Smoking and Lung Disease
Sanja Jelic, MD, is board-certified in sleep medicine, critical care medicine, pulmonary disease, and internal medicine.
Smoking marijuana is associated with respiratory problems such as chronic obstructive pulmonary disease (COPD) and recurrent lung infections. The effects are dose-dependent: The more marijuana you smoke, the higher your risk of developing respiratory issues.
Additionally, secondhand smoke from marijuana is also associated with serious breathing issues and pulmonary diseases, especially among children who are exposed to marijuana in an enclosed environment.
Respiratory Effects of Smoking Marijuana
The impact of smoking marijuana is similar to the impact of smoking cigarettes on your lungs. You are likely to experience more severe effects if you smoke both marijuana and cigarettes.
Progressive Lung Disease
As a consequence of chronically smoking marijuana, you may experience changes in your lungs that lead to symptoms such as wheezing, a cough, sputum production, and shortness of breath. These symptoms are generally worse with physical exertion, an effect that is often described as exercise intolerance.
Over time, the effects of smoking marijuana can become persistent and severe. Chronically smoking marijuana is associated with several types of lung disease, including:
- Emphysema: In addition to emphysema (damage of the air sacs in the lungs), marijuana use also increases the risk of a severe type of the disease called bullous emphysema. Bullae are air pockets that are formed in the lungs due to the breakdown of lung tissue. When these air pockets pop, they can result in a pneumothorax (collapse of the lung).
- Bronchitis: Marijuana-induced lung damage causes inflammation. Inhalation of marijuana can cause acute bronchitis that lasts for a few days or weeks, or it can cause chronic, long-term bronchitis.
Marijuana-induced damage can produce permanent changes in the structure of the lung that may cause or exacerbate one or more types of COPD.
The chemicals that you inhale as you smoke marijuana damage the protective cilia in your lungs. As such, chronic smoking can lead to a tendency to experience frequent and severe lung infections. These may be accompanied by fever, loss of appetite, and weight loss.
COPD itself makes you more prone to recurrent lung infections, so smoking marijuana when you have this lung disease only makes you more vulnerable.
Marijuana also inhibits your immune system, predisposing you to lung infections or other types of infections (such as those of the skin or ear).
What About Medical Marijuana?
At the current time, the use of medicinal marijuana is not thought to be harmful to the lungs. In general, medical marijuana is used in low doses. In addition, many medical marijuana patients chose to ingest THC and CBD through tinctures or edibles, rather than smoke.
Vaping marijuana was previously believed to be a safer route of ingestion than smoking, but a new lung disease linked to this practice has called this into question.
Known as e-cigarette or vaping product use-associated lung injury (EVALI), the condition is related to liquid-based vaping products and causes breathing difficulties that can lead to hospitalization and even death.
According to the Centers for Disease Control and Prevention (CDC), more than 80% of patients with EVALI have reported using THC vaping products, many of which contained vitamin E acetate or medium-chain triglycerides. After testing various vape liquids used by patients for a broad range of chemicals—including nicotine, THC, CBD, opioids, additives, pesticides, poisons, heavy metals, and toxins—researchers have definitively linked vitamin E acetate to the condition.
The U.S. Food & Drug Administration (FDA) recommends against THC-containing e-cigarettes and vaping products, particularly ones from informal sources like friends, family, or in-person or online dealers. There’s simply not enough research to determine safety.
Vaping marijuana flowers using a dry-herb atomizer does not appear to pose the same risk as liquid-based THC vape products, and early research found it to be a safer alternative to smoking marijuana. However, more research is needed to confirm the safety of dry-herb vaping as well.
Diagnosis of Marijuana-Induced Lung Disease
It can be difficult to know whether pulmonary symptoms are associated with marijuana use and/or whether you have experienced long-term damage to your lungs from some other cause. If you are experiencing symptoms of lung disease, your medical team may order diagnostic tests to help identify the problem.
If you are diagnosed with marijuana-induced lung disease, you may need to begin medical or surgical treatment.
Even if you have not developed respiratory symptoms, some diagnostic tests can identify early-stage lung disease, which can help in guiding your decisions about smoking marijuana. Be upfront with your doctor about your drug use.
Pulmonary Function Tests
Typically, pulmonary function tests (PFTs) can be used to assess your respiratory function. These tests can measure your inspiration (breathing in) and expiration (breathing out), as well as the amount of air that your lungs can hold. These values often change as a result of lung disease.
Your pulmonary function can be measured with a spirometer—a device that you use as you breathe in and out based on specific instructions. A spirometer can measure the volume of air that you expire and inspire at timed intervals.
- Forced vital capacity (FVC): The amount of air you can exhale from your lungs after taking in the deepest breath possible.
- Forced expiratory volume in one second (FEV1): The amount of air you can exhale in one second.
Your doctors may also determine your FEV1/FVC ratio.
Imaging Tests and Lung Biopsy
You may also need to have an X-ray, computerized tomography (CT), or magnetic resonance imaging (MRI) of your chest and lungs to identify respiratory problems.
These tests can show signs of pneumonia (a lung infection) or COPD. They can also be used to help identify the cause of a lung infection that isn’t improving with treatment, lung cancer, or a pulmonary condition that has been difficult to diagnose.
In some instances, you may need to have a bronchoscopy, which is an interventional imaging test. With this, your doctor places a camera into your breathing tubes to visualize your lungs.
You may also need a lung biopsy, which is when a sample of tissue is collected surgically so that it can be examined under a microscope.
A Word From Verywell
Cigarette smoking is by far the strongest risk factor for the development of COPD. Smoking marijuana and vaping liquid THC products are also strong risk factors for acute lung problems and serious, life-threatening chronic lung diseases. While smoking cigarettes is a strong risk factor for lung cancer, the link between marijuana and lung cancer is not well established at this time.
Chronically smoking marijuana can lead to and worsen lung diseases like COPD and cause recurrent lung infections.