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MCDA Comparison of Drug and Alcohol Harms in the UK

A chart about the Harms of drugs


David J Nutt, Leslie A King, and Lawrence D Phillips


November 1, 2010

An assessment of the various harms of drugs used recreationally in the UK using multi-criteria decision analysis (MCDA) – a method that uses relevant experts’ knowledge and experience to assess the actual and relative harms – download the paper here. You can also download the raw data here.

We wanted to assess drugs in terms of their known harms to individuals, those around them and more broadly, to domestic and international society. Showing drugs’ harms relative to each other also enables more objective and informed assessment of their harms individually and in relation to their current controls. This task is not easy because of the wide range of ways in which drugs can cause harm – from the intrinsic harms of the drugs to social and health-care costs.

To rectify these drawbacks we undertook a review of drug harms with a MCDA approach. This technology has been used successfully to lend support to decision makers facing complex issues characterised by many, conflicting objectives — e.g. appraisal of policies for disposal of nuclear waste. Sixteen harm criteria were identified by the UK Advisory Council on the Misuse of Drugs – nine relate to the harms that a drug produces in the individual and seven to the harms to others both in the UK and overseas.

Drugs were point scored out of 100, with 100 assigned to the most harmful drug on a specific criterion, and subsequently weighted between criteria.

What does it show?

The report found heroin, crack cocaine, and methamphetamine to be the most harmful drugs to individuals (part scores 34, 37, and 32, respectively), with alcohol, heroin, and crack cocaine as the most harmful to others (46, 21, and 17, respectively). Overall, alcohol was the most harmful drug (overall harm score 72), with heroin (55) and crack cocaine (54) in second and third places. It also found the legal status of most drugs bears little relation to their harms.

What does it not show?

The report does not take the legal status of a drug into account. This will undeniably have some impact on levels of harm. Alcohol’s regulated availability means that many more people have access to it than most drugs, which will have an effect on its levels of harm. Conversely, the controlled status of many drugs elevates their harm profile – unregulated production leads to chemical contamination and their stigma to risky practices such as needle sharing. The user harm rankings are likely to be largely insensitive to universal criminalisation or decriminalisation as they are intrinsically linked to their effects on mind and body. Harms to society, however, could change were a drug’s legal status changed, as observed in Portugal.

What does this mean?

This paper represents a great step forward in our understanding of drug harms but is by no means an exhaustive answer. Further work should look to expand analysis to other countries, relevant social groups, the benefits of drugs and associated user motivation. In a similar study in 2015, forty drug experts from throughout the EU scored 20 drugs on the same 16 harm criteria. Scores given by the EU experts in the study were generally very similar to the UK scores assessed by Drug Science in 2010 … Alcohol, heroin and crack emerged as the most harmful drugs (overall weighted harm score 72, 55 and 50, respectively). The remaining drugs had an overall weighted harm score of 38 or less, making them much less harmful than alcohol.

For open-access to the full report of this research, see below:

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