Answering the question of whether inhaling cannabis increases the risks of asthma and chronic obstructive pulmonary disease (COPD) has been complicated by the fact that in the past almost all cannabis smokers also smoked tobacco, so it was difficult to determine whether the observed associations between smoking cannabis and these diseases was really due to their tobacco use (confounding). Thanks to the fact that smoking cigarettes has been falling at the same time cannabis use has been increasing, Alison Rustagi, our UCSF colleagues, and I have been able to pry these effects apart. Our new paper “Inhaled Cannabis, Asthma, and Chronic Obstructive Pulmonary Disease: A Population-Based Cross-Sectional Study of n = 379,049” found a dose-response between inhaled cannabis and asthma and COPD, controlling for tobacco smoking and also among never smokers.
We studied adults 18–74 years old in the national 2016–2020 Behavioral Risk Factor Surveillance System population-based surveys of 379,049 adults. Our analysis age, sex, race/ethnicity, education, marital status, difficulty paying for medical care, body mass index, diabetes, physical activity, alcohol consumption, and smoking tobacco cigarettes.
Overall, there was a dose–response relationship between days per month of cannabis use and adjusted odds ratios (aOR) of asthma (aOR 1.44, 95% CI 1.26–1.63 for daily use; Figure A) compared to no cannabis use in the prior 30 days. When separated (stratified) by age, cannabis inhalation was associated with asthma among adults < 35 years (aOR 1.45, 95% CI 1.19–1.76 for daily use) and similarly among adults 35 + years (aOR 1.42, 95% CI 1.21–1.67 for daily use).
Cannabis use was associated with increased odds of COPD in a dose–response manner overall (aOR 1.27, 95% CI 1.10–1.46 for daily use; Figure B). Cannabis use was associated with COPD among adults < 50 years (aOR 1.39, 95% CI 1.13–1.71 for daily use) but was not significantly associated with COPD among adults 50 + years (aOR 1.13, 95% CI 0.96–1.33 for daily use). The magnitudes of the associations were similar between older and younger adults.
When analyses were restricted to 221,767 adults with no lifetime tobacco cigarette use, inhaled cannabis use was still associated with asthma (aOR 1.51, 95% CI 1.18–1.93 for daily use) in a dose–response manner, compared to those who did not use cannabis. There were also similar dose-response relationships among younger (<35 years) and older (35+) people. There was no statistically significant association between increasing frequency of cannabis use and COPD overall (aOR 1.54, 95% CI 0.92–2.57 for daily use), among adults < 50 years (aOR 1.69, 95% CI 0.88–3.26) or those 50 + years (aOR 1.20, 95% CI 0.72–1.99).
The fact that the effects of cannabis inhalation and cigarette smoking are independent and additive is important and similar to what we found for cardiovascular disease.
The risks for asthma were similar to and independent of the risks associated with current smoking (aOR 1.35, 95% CI 1.26, 1.44), but smaller than COPD (aOR 4.85, 95% CI 4.50, 5.24). Whether the differences for COPD reflect actual differences in risk, the fact that cannabis users consumer less than smokers do (a dose-response effect) or the fact that widespread and heavier cannabis use has not been common for the COPD effect to be fully manifest is not clear.
The approach and results are similar to those we found for cardiovascular disease, where cannabis use was associated with adverse outcomes, with heavier use (more days per month) associated with higher odds of adverse outcomes.
In sum, this new population-based cross-sectional study found that cannabis inhalation was consistently associated with asthma in the overall population, among adults younger and older than 35 years, and among those with no lifetime tobacco cigarette use. Inhaled cannabis was significantly associated with odds of COPD in the overall population and among adults younger than 50 years, but not to a statistically significant degree among adults older than 50 years or those with no lifetime tobacco cigarette use. The magnitude of our associations increased with frequency of cannabis use over the prior 30 days suggesting a dose–response relationship, one component of causal inference. Future research is needed to infer a causal relationship between chronic lung disease and cannabis use, which may be a potential modifiable risk factor in the development of asthma and/or COPD. As with cannabis and heart disease, clinicians should routinely ask about cannabis use in patients with asthma or COPD and advise that inhaled cannabis is not known to be safe with respect to asthma or COPD.
Consumers and policy makers take note: This study adds to the evidence contradicting the assumption that cannabis smoking is safe or even good for you.
Here is the abstract:
Background. Cannabis may cause chronic pulmonary disease. Prior studies have been limited by low cannabis exposure, lack of data on tobacco cigarettes, and/or limited numbers of those without tobacco cigarette use.
Objective. To examine whether inhaled cannabis associated with asthma and chronic obstructive pulmonary disease, independent of tobacco cigarettes.
Design. Cross-sectional analysis of population-based, nationally representative survey data.
Participants. Adults 18–74 years who participated in the 2016–2020 Behavioral Risk Factor Surveillance System surveys.
Main Measures. The exposure was past-30-day cannabis use, from 0 (0/30 days) to 1 (30/30 days). Outcomes were self-reported diagnoses by a medical professional of asthma or chronic obstructive pulmonary disease. We used multivariable logistic regression to test whether inhaled cannabis was associated with odds of disease, adjusted for sociodemographics and tobacco cigarette use (current/former/never). Pre-specified analyses restricted to those with no lifetime tobacco cigarette use.
Key Results. Among n = 379,049, n = 23,035 reported inhaled cannabis use. Inhaled cannabis was associated with asthma overall (adjusted odds ratio (aOR) 1.44, 95% CI 1.26–1.63 for daily use) and among n = 221,767 with no lifetime tobacco cigarette use (aOR 1.51 for daily use, 95% CI 1.18–1.93). Inhaled cannabis was associated with chronic obstructive pulmonary disease overall (aOR 1.27 for daily use, 95% CI 1.10–1.46), with a non-significant elevated odds of disease among those with no lifetime tobacco cigarette use (aOR 1.54 for daily use, 95% CI 0.92–2.57).
Conclusions. Inhaled cannabis was associated with asthma and chronic obstructive pulmonary disease after adjusting for tobacco cigarette use. Among those with no lifetime tobacco cigarette use, the association with asthma persisted. Cannabis may be a potential modifiable risk factor for asthma and chronic obstructive pulmonary disease.
The full citation is: Rustagi AS, Jeffers AM, Graham FJ, Cohen BE, Slatore CG, Byers AL, Glantz SA, Keyhani S. Inhaled Cannabis, Asthma, and Chronic Obstructive Pulmonary Disease: A Population-Based Cross-Sectional Study of n = 379,049. J Gen Intern Med. 2025 Sep 4. doi: 10.1007/s11606-025-09833-8. Epub ahead of print. PMID: 40906010.. It is available here. (PubMed)
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