From the Guidelines
Marijuana smoking does not have a clear association with an increased risk of lung cancer, but it may still pose respiratory risks due to the presence of carcinogens and other harmful substances in the smoke. The evidence on this topic is mixed, with some studies suggesting a potential link between heavy, long-term marijuana smoking and increased lung cancer risk, while others have not found a clear association 1. However, it is essential to note that marijuana smoke contains many of the same carcinogens as tobacco smoke, including tar and chemicals like benzopyrene and benzanthracene. When smoking marijuana, users typically inhale more deeply and hold the smoke in their lungs longer than tobacco smokers, potentially increasing exposure to these harmful substances.
Some key points to consider include:
- The average THC concentration in cannabis plants has increased dramatically over the past few decades, potentially elevating the risk for health problems 1.
- Cannabis use may have a deleterious effect on adolescent brain development and mental health 1.
- Smoking cannabis may affect lung function and is associated with pulmonary conditions like chronic bronchitis and chronic obstructive pulmonary disease; however, the link to lung cancer is unclear 1.
- A recent study found that cannabis smoking may be associated with adverse cardiovascular events, including myocardial infarction and stroke 1.
Given the potential risks and uncertainties, it would be prudent for regular marijuana users to consider alternative consumption methods, such as edibles or vaporizers, to reduce potential respiratory risks, particularly if they have other lung cancer risk factors or respiratory conditions. Additionally, users should be aware of the potential risks associated with cannabis use, including mental health and cardiovascular effects, and take steps to minimize these risks.
From the Research
Marijuana Smoking and Lung Cancer Risk
- The relationship between marijuana smoking and lung cancer risk is complex and has been studied extensively 2, 3, 4, 5, 6.
- Some studies suggest that marijuana smoking may not be a significant risk factor for lung cancer, particularly for light or moderate use 2, 4, 5.
- However, other studies have found an increased risk of lung cancer associated with heavy or long-term marijuana smoking 3, 6.
- A pooled analysis of six case-control studies found no significant association between cannabis smoking and lung cancer risk, although the possibility of potential adverse effects for heavy consumption cannot be excluded 5.
- A prospective study found that cannabis smokers were diagnosed with lung cancer at a younger age than tobacco-only smokers, but cannabis smoking was not a prognostic factor for mortality 6.
Study Findings
- A 2018 study found that smoking cannabis has not been proven to be a risk factor in the development of lung cancer, but the data are limited by small studies and confounding variables 2.
- A 2013 study found that heavy cannabis smoking was significantly associated with an increased risk of developing lung cancer over a 40-year follow-up period 3.
- A 2013 review found that regular smoking of marijuana by itself causes visible and microscopic injury to the large airways, but habitual use of marijuana alone does not appear to lead to significant abnormalities in lung function 4.
- A 2015 pooled analysis found that the overall pooled odds ratio for habitual versus nonhabitual or never users of cannabis was 0.96, indicating no significant association between cannabis smoking and lung cancer risk 5.
- A 2025 study found that cannabis smokers were diagnosed with lung cancer at a younger age than tobacco-only smokers, and had different histological types of lung cancer 6.
Limitations and Future Research
- Many studies on marijuana smoking and lung cancer risk are limited by small sample sizes, self-reported data, and confounding variables 2, 3, 4, 5, 6.
- Further research is needed to fully understand the relationship between marijuana smoking and lung cancer risk, particularly for heavy or long-term use 2, 5.
- Controlled trials with standardized dosing and accurate assessment of biologic activities of compounds in cannabis and derivative products are needed to better understand the effects of marijuana smoking on lung health 2.