Marijuana and Asthma

Editor's note: Medical marijuana (cannabis) and CBD are not legal in some states.

Marijuana (cannabis) is becoming legal in many US states. Medical marijuana may treat pain, insomnia, anxiety, and other conditions. In some states, it is only legal for medical purposes. In other states, marijuana is also legal for recreational purposes.^1,2

Experts do not recommend that people with asthma smoke or vape marijuana. Doctors do not fully understand how marijuana's chemical makeup affects the airways. But, they do know that smoking irritates the airways and worsens asthma symptoms.^1,3

What are the benefits of marijuana for asthma?

Smoking or vaping is not safe for people with asthma. The active ingredients of marijuana do have some health benefits. These active substances are called cannabinoids. The 2 main cannabinoids in marijuana are:¹

• Tetrahydrocannabinol (THC): psychoactive substance that gives a “high” sensation
• Cannabidiol (CBD): non-psychoactive substance that has anti-inflammatory properties

Because of these effects, people may use marijuana to treat anxiety, chronic pain, sleep, and inflammatory conditions. There is not enough evidence that it is safe or effective for asthma. Small studies have shown that THC may:^2,4,5

• Have mild bronchodilator effects (open up the airways)
• Suppress immune system activity
• Reduce airway inflammation

These benefits do not outweigh the risk of inhaling smoke in people with asthma. We need more research to understand how safe or effective marijuana is in asthma. But marijuana use is hard to study. This is because many people who smoke marijuana also smoke tobacco. And people smoke different types of marijuana in different frequencies.^4,5

What are the risks of marijuana for asthma?

Marijuana has serious risks for people with asthma. Smoking poses the largest risk. Smoking any substance irritates the airways. This can make asthma symptoms worse. For people with asthma, smoking marijuana is linked to:^2,3,5

• Higher risk of asthma attacks
• More frequent coughing
• More phlegm (sputum)
• Shortness of breath
• More frequent wheezing
• Bullous lung disease (developing air sacs in the lung)
• Pneumothorax (collapsed lung caused by ruptured air sacs)

These risks apply to people who smoke only marijuana, only tobacco, or both. The risks may be the direct effects of airway irritation. The risks may also be linked to poor management of treatments and triggers.²

Marijuana can cause allergic reactions. THC and other components may be allergens. This may be a concern for people exposed to marijuana at work.²

These are not all the possible risks of marijuana. Other side effects are possible, including poor memory and focus. Talk to your doctor if you notice changes while using marijuana.⁶

Are different forms of marijuana safer?

Many different products are out there. They vary in terms of their CBD and THC content. Each person responds differently to different ratios of CBD and THC. Marijuana products also vary in how you use them.¹

Smoking marijuana is the most common way to use it. Smoking may be the most unsafe way for people with asthma. Other ways to use it include:¹

• Oral: using extracts in foods, capsules, or supplements
• Topical: applying oils to your skin

Oral or topical forms are less likely to irritate your lungs. They may not have any benefits for asthma. But they may help treat chronic pain and other conditions. Talk to your doctor about whether these forms are safe for you. Your doctor may suggest keeping a log of symptoms to see how marijuana affects you.^1,3