A Global Day for Prevention

World Cancer Day, observed globally on February 4th, unites people across more than 100 countries in the fight against cancer. This year, the evidence demands we address two substances that significantly increase cancer risk yet remain widely misunderstood: alcohol and cannabis.

The International Agency for Research on Cancer classifies alcohol as a Group 1 carcinogen, placing it alongside tobacco and asbestos. Globally, alcohol consumption is associated with 740,000 new cancer cases every year. Cannabis, increasingly normalized through legalization worldwide, carries serious cancer risks that are only now being properly studied.

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At World Resiliency Day, we believe genuine resilience comes from making informed choices based on evidence, not cultural assumptions or marketing messages.

The Alcohol-Cancer Connection: No Safe Level Worldwide

People across the world believe light to moderate drinking poses minimal health risks. Research challenges this assumption directly.

Across the European Union, light to moderate alcohol consumption (fewer than 20 grams of pure alcohol daily) was associated with nearly 23,000 new cancer cases in 2017. More than one-third occurred in individuals consuming fewer than 10 grams per day—equivalent to less than one standard drink.

When consumed, alcohol metabolizes into acetaldehyde, a toxic compound that damages DNA and prevents cells from repairing damage. Alcohol produces reactive oxygen species that harm DNA, proteins, and lipids. In women, alcohol increases oestrogen levels, directly linked to breast cancer risk.

The global scientific consensus is unequivocal: no safe threshold exists for alcohol and cancer prevention.

Alcohol is causally linked to seven cancer types: breast, liver, colorectal, oesophageal, mouth, throat, and larynx. This pattern holds true worldwide, affecting populations across all continents.

Read Full Research Analysis

Cannabis: The Global Cancer Risk Being Ignored

As cannabis becomes more socially acceptable and legally accessible across North America, Europe, and other regions, emerging international research reveals serious cancer risks that public health campaigns have largely ignored.

Head and Neck Cancers: Research published in JAMA Otolaryngology found that heavy cannabis users are 3.5 to 5 times more likely to develop head and neck cancers than non-users. A 2024 study found that cannabis use disorder triples the risk of oral cancer specifically.

The Smoke Contains Carcinogens: Cannabis smoke contains many of the same carcinogenic compounds found in tobacco smoke, in some cases in higher concentrations. These compounds damage epithelial tissue lining the mouth and respiratory system.

THC’s Immune-Suppressing Effects: THC, the active compound in cannabis, has immune-suppressing effects that may contribute to increased cancer risk. Two proto-oncogenes are overexpressed in the bronchial epithelium of marijuana-only smokers.

Testicular Cancer: International evidence suggests cannabis use is associated with testicular germ cell tumors, predominantly affecting younger men.

Critically, the association between cannabis use disorder and head and neck cancers remained even after controlling for tobacco and alcohol use, demonstrating cannabis carries independent cancer risk.

Australia’s Context

Australians aged 15 and over consumed 10.6 litres of alcohol per capita in 2016, substantially higher than the global average of 6.4 litres. Over one-third reported heavy episodic drinking within 30 days.

An Australian study following 226,162 participants revealed the risk of alcohol-related cancers increased by 10% with every additional seven drinks per week. By age 85, absolute cancer risk reached 17.3% in men and 25.0% in women consuming more than 14 drinks weekly, compared to 12.9% in men and 19.6% in women consuming less than one drink per week.

These patterns mirror global trends, demonstrating that cancer risk from alcohol and cannabis transcends geography and culture.