Cannabis & Asthma: Risks and Benefits

Numerous studies have been published on the medical uses of cannabis for chronic pain, epilepsy, multiple sclerosis, cancer, anxiety, and PTSD. Research and knowledge about cannabis use in those with asthma is limited, however. Because people with asthma are at high risk for adverse effects from inhaling cannabis, determining patterns of use, impact on respiratory function, and benefits in this population is essential.

In April 2021, researchers from the Canna Research Foundation (CRF) and Allergy & Asthma Network (AAN) published results of an anonymous online survey—the Pain, Exercise, and Cannabis Experience, or PEACE, survey—on cannabis use and attitudes in asthma patients aged 18 and older. Participants were recruited through AAN, a patient advocacy group that unites and educates Americans with asthma, allergies, and related conditions.

“The aims of this study were to examine knowledge, attitudes, and patterns of cannabis use among people with asthma and allergies,” says Joanna Zeiger, MS, PhD, founder and CEO of CRF, a nonprofit organization of cannabis outcomes researchers who conduct and consult on research studies of cannabis patterns of use, benefits, adverse effects, and knowledge/attitudes in medical cannabis users. CRF also provides evidence-based consulting and education to cannabis industry stakeholders, physicians, dispensaries, and patients. Data from 489 respondents were analyzed.

The demographics and health behaviors of the surveyed patients included the following:

• 60.2% were younger than 50.
• 72.4% were female.
• 71.6% were white.
• 71.5% were college graduates, with 33.3% holding an advanced degree.
• 80.5% were employed, and 61.9% had a yearly household income of at least $70,000.
• 63.2% used alcohol in the month prior to the survey.
• 4.9% smoked cigarettes, and 2.5% used e-cigarettes/vapes in the month prior to the survey.

Of those surveyed, 55.6% reported having received a physician diagnosis of asthma at some time, and 50.1% reported currently having asthma. Of those with asthma, approximately 40% had asthma considered to be uncontrolled. A key finding, according to Zeiger, was that 18% of survey respondents had used cannabis in the past two weeks. Notably, this frequency of use is higher than that reported for the general population without a medical condition (8.3%) or with a medical condition (8.8%).1

Of those using cannabis long term, approximately 75% reported that the route of cannabis administration was smoking, while 49% reported vaping cannabis. “The biggest surprise was the number of cannabis users with asthma that used cannabis via inhalation methods, particularly those with uncontrolled asthma, even if they reported coughing or shortness of breath,” Zeiger states. The survey analysis indicated that 50% of those with uncontrolled asthma reported smoking cannabis and coughing as a result.1

Survey results indicated that cannabis users believed the benefits of cannabis outweighed its adverse effects, and knowledge and attitudes influenced usage. “Cannabis users had the most supportive attitudes and the most knowledge about cannabis,” Zeiger notes. Users reported the following benefits associated with their cannabis use: sleep aid (75%), pain relief (68%), calming (68%), and anxiety reduction (67%). The most frequently reported adverse effects were increased appetite (29%), coughing (19%), shortness of breath (7%), and itchy eyes (6%).1

The survey suggests that those with asthma are using cannabis for health benefits, even though it might aggravate asthma symptoms over the long term. “Inhaled routes of cannabis, ironically, can actually cause bronchodilation, meaning that in the short term, it can open airways,” Zeiger explains. In fact, cannabis was used as an asthma treatment by medical practitioners in the 19th century.2 “However, over the long term, the effects on the lungs can be deleterious, as seen with patients reporting coughing and shortness of breath,” she adds. Regarding the overall health of the lungs, Zeiger notes that studies are still being conducted to determine exactly how cannabis affects the lungs.

Research Into Cannabis and Lung Health
Even with the increasing legal availability of noninhaled cannabis products, smoking remains the most common method of consumption for adult recreational use and many medical uses due to a rapid onset of action when inhaled. Because cannabis is smoked differently than tobacco, its effects on the lungs may be amplified. Compared with tobacco smoking, cannabis is smoked without a filter and at a higher temperature. The smoke is inhaled more deeply and held in the lungs longer, and then a prolonged Valsalva maneuver is performed; this method of inhalation/exhalation is intended to result in a more rapid absorption of THC. But this also leads to a greater retention in the lungs of carbon monoxide, tar, and other chemicals, such as ammonia, hydrogen cyanide, and nitrogen oxides, that are produced by combustion of the cannabis plant. Such exposure is of concern to those with asthma, who are often sensitive to chemical exposure. Inhalation of chemical odors and aerosols can trigger asthma symptoms. Interestingly, though, epidemiological studies and other research haven’t definitively proven that cannabis smoking is linked to an increased incidence of lung cancer as is tobacco smoking.2,3

Other adverse respiratory effects have been linked to cannabis smoking and are of concern for those with asthma. Research has shown that regular cannabis smoking is associated with increased prevalence of coughing, wheezing, sputum production, shortness of breath, and acute respiratory conditions (eg, bronchitis) in those without asthma. Studies of cannabis smoking and asthma documented worsening asthma symptoms, increased exacerbations, and development of new asthma symptoms. One study found that asthma exacerbations doubled in cannabis smokers compared with non–cannabis smokers. Smaller studies and case reports have shown other lung complications associated with cannabis smoking, including emphysema, hypersensitivity pneumonitis, eosinophilic pneumonitis, hemoptysis, acute respiratory distress syndrome, and aspergillosis.2,3

In addition to having higher rates of asthma symptoms and other respiratory issues, research has shown that asthma patients who smoke cannabis may not achieve management of their asthma and have a greater number of emergency department visits than those of asthma patients who don’t smoke cannabis.3 As mentioned previously, the results of the AAN/CRF survey showed that 50% of respondents who smoked cannabis reported that their asthma was uncontrolled. The cannabis users with uncontrolled asthma reported poorer quality of life and a higher frequency of hyperventilation.1

Another emerging side effect that has attracted more attention with increasing cannabis use due to legalization is cannabis allergy. In the AAN/CRF survey, 2.5% of non–cannabis users indicated they were allergic to cannabis.1 There’s only limited research on cannabis allergies, and the specific allergens haven’t yet been identified. Research suggests that cannabis allergies can range from mild to severe, and reactions can occur with inhalation (smoking or plant pollen), skin contact, or ingestion. Similar to allergies to other substances, cannabis allergy symptoms may include rhinitis, sneezing, conjunctivitis, and wheezing in mild cases, and throat edema, chest tightness, vomiting, and anaphylaxis in severe cases. Because allergies are common in those with asthma, and allergic reactions can trigger asthma symptoms, including severe exacerbations, cannabis allergy should be considered and evaluated in asthma patients who use cannabis.2,3

Benefits of Cannabis for Asthma
Despite its adverse effects when smoked, cannabis does have benefits for those with asthma—when it’s consumed in another form. The two primary cannabinoid receptors in the body, CB1 and CB2, are found in the lungs. CB1 receptors are located throughout the bronchial smooth muscle tissue and may regulate bronchial muscle tone. CB2 receptors are found on alveolar macrophages, as well as lymphocytes, and assist in modulating inflammation. Because asthma is an inflammatory disorder, cannabis may have beneficial effects by facilitating bronchodilation, decreasing inflammation and allergen-induced mucus production, and reducing anxiety and emotional stress that may contribute to asthma attacks.4

As mentioned previously, more than two-thirds of asthma patients surveyed by the AAN/CRF reported using cannabis for anxiety reduction. Research has shown that anxiety may be up to six times more prevalent in those with asthma compared with those without it. And the prevalence of anxiety is even higher for those with more severe asthma.5,6 Anxiety relief is one of the most common reasons for cannabis use that’s also backed by scientific and anecdotal evidence.7

Safer Administration Routes for Asthma
With recent research confirming the dangers of smoking cannabis for those with asthma, increasing awareness of alternative routes of administration is necessary. Vaping has been associated with lung problems and isn’t recommended for those with asthma. Waterpipe/hookah inhalation hasn’t been well studied in those with asthma. Although it eliminates combustion, the water doesn’t filter out harmful chemicals, and waterpipe inhalation may confer higher carbon monoxide levels than does smoking.2,3

Vaporizers or nebulizers, which move air using heat or compression across the cannabis rather than burning it, may be a safer option than smoking, although their use hasn’t yet been adequately studied.2,3 Some companies have developed cannabis nebulizers and other types of inhalers appropriate for use by those with asthma, but they aren’t yet commonly prescribed in the United States.

With expanding legalization of cannabis and increasing access to dispensaries with a variety of topicals, tinctures, and edibles, there are safer options for those with asthma who wish to use cannabis. While their onset of action isn’t as rapid as seen in inhalation, oral and topical use has the lowest risk of respiratory side effects in those with asthma. Zeiger and her colleagues suggest that, given the potential detrimental effects of smoking or vaping cannabis, “edibles, tinctures, topicals, or less common routes of use (eg, suppositories or sprays) are more appropriate routes for cannabis use.”1

Guidance for Health Care Professionals
Awareness and attention to cannabis issues in asthma patients is currently lacking among the medical professionals who treat them. Only approximately 34% of asthma/allergy physicians inquired about cannabis use verbally or on a patient intake form, according to the AAN/CRF survey. Zeiger and her colleagues are collecting data on knowledge, attitudes, and practices regarding cannabis among an international group of allergists recruited from their respective professional medical societies. In November 2021, they presented a preliminary analysis of survey results.8 “We found that 22% of allergists did not ask about cannabis use, 61% did not include cannabis use on their intake form, and 32% were uncomfortable talking to patients about cannabis,” Zeiger notes.

Only a small percentage of cannabis users wanted to discuss cannabis use with their physicians, possibly fearing their negative reaction to cannabis use and recommendations to stop use. Zeiger and her colleagues call attention to this lag between patient adoption of cannabis for therapeutic reasons and physician recognition of patient use, which is a missed opportunity for education regarding the effects of cannabis on asthma symptoms.1

Zeiger advises that health care professionals should be informed about the basics of cannabis, its benefits and adverse effects, and the various routes of administration. Additionally, conversations with patients should be open and nonjudgmental. As mentioned previously, many patients have comorbid conditions for which they use cannabis, such as chronic pain, muscle spasms, insomnia, and anxiety. Because many of the AAN/CRF survey participants who used cannabis experienced benefits from it, recommending cessation might be difficult and not well accepted by patients, Zeiger notes. “Instead, it is important to differentiate to the patient the benefits and harms of the various routes of administration and focus on recommending substituting inhaled routes with topicals, edibles, and tinctures,” Zeiger recommends. “Cessation is not always an option, but changing the route of administration could be a happy compromise,” she says.

— Jennifer Van Pelt, MA, is a freelance writer and health care researcher located in the Lancaster, Pennsylvania, area.

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