Does cannabis increase the risk of cancer?

Some studies have linked regular cannabis use to an increased risk of certain cancers. What's the reason? (Image: Catherine Falls Advertising/Getty Images)

Cannabis smoke may be perceived as less aggressive than tobacco smoke, but this impression can be misleading. Current data indicate that chemical components of cannabis can have a negative effect on the deep processes of lung tissue. Some studies by scientists have found a correlation between intensive cannabis use and the risk of developing oncological pathologies, including tumors of the head and neck.

Is there a proven link between cannabis and cancer, and if so, what are the underlying mechanisms?

Each inhalation of smoke contains tetrahydrocannabinol (THC), microparticles and carcinogens, also characteristic of tobacco. However, cannabinoids can have a specific effect, gradually changing the immune reactions in the pulmonary system.

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“A decrease in the barrier function of the airways, a weakening of the antiviral response, and an increase in inflammatory reactions,” comments Rafael Cuomo, a specialist in the field of cancer prevention and addiction therapy at the University of California, San Diego. Experiments on animal models have shown that cannabis can suppress antitumor and antiviral immunity. Other work has shown that THC reduces the effectiveness of immunotherapy by disrupting the functionality of cells responsible for destroying tumors.

Clinical, cellular, and preclinical studies have shown that cannabis induces a variety of changes in immune function. Chronic use in the respiratory tract results in significant increases in inflammatory proteins. Excessive production of MUC5AC mucin in individual cells indicates the early stages of tissue transformation, and cannabis smoke can disrupt enzyme activity that maintain tissue homeostasis and block genes that respond to toxins.

Alveolar macrophages, the lungs' immune guardians, show a slow response. The circulatory system registers changes in the cytokine profile and minor epigenetic modifications that record the impact.

In short, “cannabis smoke, including THC and other toxic components, can irritate lung tissue and suppress immune defenses,” Sayantan Bhattacharya, a systems biologist at MD Anderson Cancer Center, told Live Science.

However, immunosuppression is only one factor in potential cancer risk. Smoking cannabis can activate intracellular mechanisms, including molecular pathways used by malignant cells to proliferate and metastasize.

One of the key players in this process is the epidermal growth factor receptor (EGFR). In a unique study, Bhattacharya analyzed data from 83 patients with laryngeal cancer and found that cannabis users had increased activity of EGFR and tumorigenesis-related proteins compared to tobacco smokers or individuals without harmful habits.

“EGFR regulates cell growth, regeneration, and survival,” the scientist explains. “Its chronic activation in cannabis users may stimulate uncontrolled cell division, increase genetic damage, and accelerate cancer development, contributing to early onset, aggressive progression, and resistance to therapy.” It is important to note that the findings of the study, which is based on a limited sample of patients with a specific tumor type, require further confirmation.

Bhattacharya identifies two areas for future research: developing realistic laboratory models (organoids, 3D tumors, organ chips) to study the effects of cannabis on EGFR, and analyzing potentially harmful additives in unregulated products.