Disease Risk Profiling: Alcohol is a Group 1 Carcinogen

The International Agency for Research on Cancer (IARC), part of the World Health Organization, classifies alcohol as a Group 1 carcinogen — the highest risk category, reserved for substances with conclusive evidence of causing cancer in humans. It shares this classification with asbestos, formaldehyde, and tobacco. Cannabis is not classified as a carcinogen by IARC or WHO. [IARC/WHO]

Alcohol directly causes seven distinct types of cancer: breast, liver, colon, esophageal, oral, pharyngeal, and laryngeal. In the United Kingdom alone, alcohol accounts for approximately 3.3% of all cancer cases — around 11,900 new diagnoses every year. The mechanism is well understood: ethanol metabolises into acetaldehyde, a genotoxic compound that damages DNA and prevents cells from repairing that damage. Every drink increases the risk. [GBD/Lancet]

The cardiovascular effects of alcohol are equally devastating. Chronic consumption causes persistent hypertension, atrial fibrillation, dilated cardiomyopathy, and haemorrhagic stroke. Alcohol is a leading cause of premature cardiovascular death in adults aged 15 to 49. The so-called "J-shaped curve" — the idea that moderate drinking protects the heart — has been thoroughly debunked by modern Mendelian randomisation studies, which show that any cardioprotective effect is an artefact of confounding variables. [World Health Organization]

The psychiatric toll is staggering. Alcohol is strongly correlated with clinical depression, anxiety disorders, suicide, and permanent cognitive decline. An estimated 10 to 24% of all dementia cases in the UK are linked to alcohol consumption. Cannabis, by contrast, carries conditional psychiatric risks: it can trigger or accelerate early-onset psychosis in individuals with a pre-existing genetic vulnerability, but the baseline risk for the general population is low, and cognitive effects are reversible with cessation. [GBD/Lancet]

Fatal overdose is where the difference becomes absolute. Alcohol causes fatal respiratory depression at high doses, killing thousands annually through acute poisoning. Cannabis has a lethal dose that is so high it cannot realistically be reached — the MOE exceeds 10,000, and no CB1 receptors exist in the brainstem to mediate respiratory collapse. Physical dependence follows a similar pattern: around 15% of regular alcohol users develop dependence, and withdrawal (delirium tremens) carries a mortality rate of up to 5%. Cannabis dependence affects roughly 9% of regular users, but withdrawal, while uncomfortable, is never fatal. [Lachenmeier & Rehm (2015)]

The WHO estimates that alcohol contributes to more than 200 disease and injury conditions. No other recreational substance comes close. Explore the full physical toll in our Body Health Effects section.

Sources: [IARC/WHO] | [GBD/Lancet] | [Lachenmeier & Rehm (2015)]