Oral Cancer Risk Jumps with Heavy Cannabis Use

As cannabis use becomes more mainstream in North America, a new study¹ has raised questions about the long-term health effects of chronic, problematic use, particularly as it relates to oral cancer.  Published in Preventive Medicine Reports, it found that individuals diagnosed with cannabis use disorder (CUD) were more than three times as likely to develop oral cancer over a five-year period compared to those without the disorder.

Understanding the Study: A Closer Look

The research, led by Raphael E. Cuomo from the University of California, San Diego, examined electronic health records from over 45,000 patients across six academic medical centers in California.  Patients included in the study had no prior diagnosis of oral cancer and were initially screened for drug use disorders between 2012 and 2019.  They were then followed for five years to see if they developed oral cancer, specifically on the lip or tongue.

Out of the total participants, 949 individuals (2.1%) were diagnosed with CUD during the follow-up period.  While the overall rate of oral cancer was low, only 0.23% in the non-CUD group developed it, compared to 0.74% among those with CUD.

After adjusting for age, sex, body mass index (BMI), and tobacco smoking, the study found that those with CUD had a more than threefold increase in risk of developing oral cancer.

Why This Matters: Cannabis Is Not Risk-Free

While in many instances, cannabis consumption is viewed as relatively benign (edibles, tinctures, etc), the results show that this is not the case with excessive use through inhalation.  Cannabis combustion produces many of the same carcinogens as tobacco, including polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs), both of which are known to damage DNA and increase cancer risk.

Unlike previous studies that relied on self-reported cannabis use, which can be inaccurate or incomplete, this study used a clinical diagnosis of cannabis use disorder as a proxy for frequent, sustained use.  In doing so, it gives it a degree of reliability that strengthens the case for concern.

The Biological Link: How Cannabis Smoke May Harm the Mouth

Oral cancers most commonly arise in tissues directly exposed to smoke and heat.  Cannabis, when smoked, exposes the delicate mucosal linings of the mouth and throat to high temperatures and toxic compounds.  Chronic exposure can lead to cellular changes such as epithelial dysplasia – abnormal development of tissue that often precedes cancer.

Interestingly, even among tobacco smokers, those with CUD were found to have significantly higher odds of developing oral cancer compared to smokers without CUD.  This suggests the combined exposure may be synergistic rather than additive, compounding the health risks.

Beyond combustion, cannabis may also impair immune function.  The plant’s main psychoactive compound, THC (tetrahydrocannabinol), has been shown to suppress various aspects of immune response, including natural killer cells that help eliminate precancerous cells.  Over time, this may reduce the body’s ability to fend off the development of tumors.

Who Is Most at Risk of Oral Cancer from Cannabis Use?

While it’s tempting to dismiss this risk as relevant only to stereotypical “heavy users,” the clinical diagnosis of CUD generally reflects a consumption pattern of about 14 joints per week or more. With the growing popularity of cannabis, particularly high-potency strains and concentrates, this level of use is no longer uncommon.

Moreover, younger adults, especially males, represented a large portion of those diagnosed with CUD in the study.  That points to a significant demographic shift—one where long-term cannabis exposure may become a more prevalent issue, especially if use begins in adolescence and continues for decades.

A Necessary Note: Cannabis Also Offers Benefits

While the study raises important concerns, it is important to recognize that cannabis is not inherently harmful.  In fact, when used responsibly and appropriately, cannabis offers a range of therapeutic benefits that have been widely studied and increasingly accepted in medical practice.

Medical Benefits Include:

• Pain relief: Particularly in chronic pain conditions like fibromyalgia, arthritis, and neuropathy.
• Anti-nausea effects: Especially beneficial for patients undergoing chemotherapy.
• Appetite stimulation: Useful in treating wasting syndromes such as those associated with HIV/AIDS or cancer.
• Reduction in seizure frequency: Notably seen in conditions like Dravet syndrome and Lennox-Gastaut syndrome through CBD-dominant medications.
• Mental health support: Some users report relief from anxiety, PTSD, and depression, though evidence is still evolving and use must be carefully monitored.

Moreover, cannabis has been associated with a reduction in opioid use for pain management, potentially contributing to fewer overdoses in regions where medical cannabis is legal.

Importantly, most of these benefits are associated with responsible, often non-smoked use, and at medically appropriate doses.  Cannabis use disorder, by contrast, reflects problematic and often heavy patterns of use that go beyond medical guidance or occasional recreational consumption.

Study Limitations and Future Research

Like all research, this study has limitations.  It relied on diagnostic coding within medical records, meaning that some cases of CUD or oral cancer may have gone unrecorded.  The study also lacked detailed data on alcohol use, HPV status, and socioeconomic variables – all known contributors to oral cancer risk.

Additionally, it did not account for how cannabis was consumed.  With the rising popularity of vapes, edibles, and oils, future studies will need to distinguish between combustion-based and non-combustion-based exposure to accurately assess relative risks.

Understanding Cannabis Risks and Responsible Use

This study should not be seen as a condemnation of cannabis.  Like many substances, its effects exist along a spectrum, from therapeutic to harmful, depending on frequency, dose, method, and user profile.  But as cannabis becomes more normalized, so should conversations about its risks.

The key takeaway is this: Just because something is legal or natural does not make it risk-free.  With more people turning to cannabis for both medical and recreational purposes, understanding its long-term impact, especially on oral and respiratory health, is a public health imperative.  Cannabis education must evolve, not just to celebrate its benefits, but to responsibly acknowledge and address its potential harms.

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