The Scale of Harm: Alcohol Scores 79/100, Cannabis 15/100
How the Multi-Criteria Decision Analysis framework ranks substances — and why alcohol is the most destructive substance known to humanity.
In 2010, a team led by Professor David Nutt and the Independent Scientific Committee on Drugs published a landmark study in The Lancet that would forever change how scientists think about drug harm. Using a framework called Multi-Criteria Decision Analysis (MCDA), the researchers asked a simple question: if we judge drugs not by legal classification but by objective measures of harm — to the user, to others, and to society — how do they truly compare? [Nutt et al. (2010, The Lancet)]
The answer was explosive. Alcohol scored 72 out of 100 — the highest of any substance, surpassing heroin (55), crack cocaine (54), and methamphetamine (33). Cannabis scored 20. The legal status of these substances bore almost no relation to their scientific harm profile. Alcohol, the most harmful drug overall, was legal and aggressively marketed. Cannabis, among the least harmful, carried criminal penalties. [Nutt et al. (2010, The Lancet)]
How the MCDA Framework Works
The MCDA framework evaluates substances across 16 distinct criteria, divided into two primary vectors. The first is harm to the user, covering 9 criteria: drug-specific mortality (the direct risk of fatal overdose), drug-related mortality (deaths secondary to use such as accidents and organ disease), drug-specific damage (direct tissue and cellular destruction), drug-related damage (secondary health issues), dependence, drug-specific impairment of mental functioning, loss of tangibles (financial ruin, homelessness), and loss of relationships. [Nutt et al. (2010, The Lancet)]
The second vector is harm to others, covering 7 criteria: injury (including domestic violence, bar fights, assault, and traffic accidents), crime (acquisitive and violent), family adversities (emotional toll, child neglect, generational breakdown), decline in community cohesion (public nuisance, anti-social behaviour), economic cost (healthcare, policing, court resources, lost productivity), environmental damage, and international damage (funding cartel violence, human trafficking, political destabilisation).
Each criterion is weighted by expert panels, producing a composite score that reflects the totality of harm. Crucially, the "harm to others" vector is where alcohol completely distances itself from every other substance. Alcohol ranked number one in 9 out of the 16 harm criteria — more than any other drug. [Journal of Psychopharmacology (2026, CIHR-funded)]
The 2010 Scores vs. The 2026 Update
In 2026, the MCDA framework was updated by an international coalition of addiction specialists, epidemiologists, and public health academics from institutions across Canada, the United Kingdom, and New Zealand, fully funded by the Canadian Institutes for Health Research (CIHR). The updated ranking evaluated 16 core substances across the same 16 harm categories. [Journal of Psychopharmacology (2026)]
| Substance | Overall Harm Score | Key Drivers |
|---|---|---|
| Alcohol | 79 | Ranked #1 in 9 of 16 criteria: physical damage, relationship destruction, injury risk, family adversity, economic costs. |
| Tobacco | 45 | Driven by chronic physical mortality and individual health degradation. |
| Non-prescription Opioids | 33 | High acute overdose lethality (illicit fentanyl, nitazenes). |
| Cocaine | 19 | Personal health damage and systemic black-market violence. |
| Methamphetamine | 19 | Psychological dependencies and localised social disruption. |
| Cannabis | 15 | Remarkably low in acute toxicity and physical harm. Score inflated by prohibition-driven illicit market. |
A Crucial Nuance: Why Cannabis Scores 15, Not Zero
One of the most important findings from the 2026 study is why cannabis registered a score of 15 instead of zero. The researchers noted that cannabis's highest weighted sub-score was not driven by the plant's biology or toxic effects on the human body. Instead, its score was heavily inflated by organised criminal activity and the illicit market in regions where it remains prohibited. In other words, a significant portion of the remaining "harm" attributed to cannabis in modern academic models is artificially manufactured by the laws that keep it illegal — rather than the substance itself. [Journal of Psychopharmacology (2026)]
Alcohol's score of 79, by contrast, is driven by the sheer physical and social wreckage caused by the drug being legally and widely available. The sub-scores tell the full story: alcohol's "harm to others" component of 46 (out of 50) is the highest of any substance — reflecting its dominant role in violent crime, family breakdown, and economic costs. Its "harm to the user" component of 26 reflects the direct biological damage from a Group 1 carcinogen that causes liver cirrhosis, heart disease, and seven types of cancer. [Nutt et al. (2010, The Lancet)]
For a side-by-side comparison of all 18 substances across every harm criterion, visit our full Substance Matrix. To see how alcohol and cannabis compare on specific harm dimensions, explore the Harm Matrix.
Sources: [Nutt et al. (2010, The Lancet) — Original MCDA Framework] | [Journal of Psychopharmacology (2026, CIHR-funded Update)] | [Canadian Institutes for Health Research] | [Lachenmeier & Rehm (2015), Margin of Exposure Analysis] | [Rolles & Measham (2011), Methodological Critique]