Cannabis use may be linked to respiratory issues and altered immune function, according to a new study published in the European Respiratory Journal on March 3, 2026. The research, conducted by scientists in Canada, the United States, and the United Kingdom, provides a detailed look at the effects of cannabis smoking on lung health and the body’s defense systems. Understanding these potential impacts is increasingly important as cannabis legalization and use continue to rise globally.
Researchers examined 139 individuals who smoked cannabis, alongside a control group of 57 non-smokers. To standardize comparisons, they used a metric called “joint-years,” representing the equivalent of smoking one joint per day for a year.
Participants who smoked cannabis were categorized based on their level of consumption:
- Low consumption: up to five joint-years (44 percent of cannabis smokers)
- Moderate consumption: more than five to 20 joint-years (28 percent)
- High consumption: more than 20 joint-years (28 percent)
The study similarly found that 84 percent of cannabis smokers reported current or past use of tobacco or e-cigarettes.
More Respiratory Symptoms, Reduced Lung Capacity
Compared to non-smokers, those who smoked cannabis exhibited poorer lung function and reported experiencing respiratory symptoms more frequently. These included coughing, wheezing, and shortness of breath.
individuals with high levels of cannabis consumption were more likely to experience bronchitis.
Changes in the Immune System
Researchers also analyzed cells from the lining of the airways and observed changes in immune system responses. Specifically, they identified:
- An increased Type-2 immune response, which plays a role in allergic inflammation.
- A weakened Type-17 immune response, important for defending against certain germs.
- Increased activity of the MUC5AC gene, which controls mucus production in the airways.
The study authors emphasize the importance of recognizing potential health consequences as cannabis use becomes more widespread. The findings could inform future research into the long-term effects of cannabis on respiratory health.
Future studies should follow a larger number of participants over a longer period. Researchers also plan to investigate whether these symptoms and changes are reversible if individuals stop smoking.
Source
Leung, C. Et al: Clinical, physiological, imaging and molecular responses to cannabis smoking: the Canadian Users of Cannabis Smoke (CANUCK) study. In: Eur Respir J 2026, 67 (1)
