In an Article published Online First and in an upcoming Lancet, drugs experts present a new scale of drug harm that assesses both harm to the individual and harm to others. Their analysis shows that when both factors are combined, alcohol is the most harmful drug, followed by heroin and crack. The paper is written by Professor David Nutt (Imperial College London, UK, and the Independent Scientific Committee on Drugs [ISCD]), Dr Leslie A King (UK Expert Adviser to the European Monitoring Centre for Drugs and Drug Addiction [EMCDDA]), and Dr Lawrence Phillips, London School of Economics and Political Science, London, UK. The paper launch coincides to a major summit in London: Drug science and drug policy: Building a consensus.
Drugs including alcohol and tobacco products are a major cause of harms to individuals and society. To provide better guidance to policy makers in health, policing, and social care, the harms that drugs cause need to be properly assessed. This task is not easy because of the wide range of ways in which drugs can cause harm. A previous attempt to do this assessment (Nutt and colleagues, Lancet, 2007) engaged experts to score each drug according to nine criteria of harm, ranging from the intrinsic harms of the drugs to social and health-care costs. This analysis provoked major interest and public debate, although it raised concerns about the choice of the nine criteria and the absence of any differential weighting of them.
To rectify these drawbacks, the authors undertook a review of drug harms with the multicriteria decision analysis (MCDA) approach. MCDA technology has been used successfully to lend support to decision makers facing complex issues characterised by many, conflicting objectives—eg. policies for disposal of nuclear waste.
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. These harms are clustered into five subgroups representing physical, psychological, and social harms. Drugs were scored with points out of 100, with 100 assigned to the most harmful drug on a specific criterion. Zero indicated no harm. Weighting subsequently compares the drugs that scored 100 across all the criteria, thereby expressing the judgment that some drugs scoring 100 are more harmful than others. Explaining their model, the authors say: "In scaling of the drugs, care is needed to ensure that each successive point on the scale represents equal increments of harm. Thus, if a drug is scored at 50, then it should be half as harmful as the drug that scored 100." They add that a zero means no harm is caused.*
The nine categories in harm to self are drug-specific mortality, drug-related mortality, drug-specific damage, drug-related damage, dependence, drug-specific impairment of mental function, drug-related impairment of mental functioning, loss of tangibles, loss of relationships, and injury. The harm to others categories are crime, environmental damage, family conflict, international damage, economic cost, and decline in community cohesion. (For all definitions see page 3 full paper).
Overall, MCDA modelling showed alcohol was the most harmful drug (overall harm score 72), with heroin (55) and crack (54) in second and third places. Heroin, crack, and crystal meth were the most harmful drugs to the individual, whereas alcohol, heroin, and crack were the most harmful to others. The other drugs assessed followed in this order in terms of overall harm: Crystal meth (33), cocaine (27), tobacco (26), amphetamine/speed (23), cannabis (20), GHB (18), benzodiazepines (eg valium) (15), ketamine (also 15), methadone (14), mephedrone (13), butane (10), khat (9), ecstacy (9), anabolic steroids (9), LSD (7), buprenorphine (6), mushrooms (5).
Thus the new ISCD MCDA modelling showed that as well as being the most harmful drug overall, alcohol is almost three times as harmful as cocaine or tobacco. It also showed that alcohol is more than five-times more harmful than mephedrone, which was recently a so-called legal high in the UK before it was made a class B controlled drug in April 2010. Ecstasy, which has had much harm-related media attention over the past two decades, is only one eighth as harmful as alcohol in this new analysis.
The authors say that their work correlates with both the previous analysis by Nutt and colleagues and that of other such as the Dutch addiction medicine expert group. However, there is almost no relation between the results and the current UK drug classification system based on the UK Misuse of Drugs Act (1971).
Professor Nutt says**: "What a new classification system might look like would depend on what set of harms—to self or others—you are trying to reduce. But if you take overall harm, then alcohol, heroin and crack are clearly more harmful than all others so perhaps drugs with a score of 40 or more could be class A; 39 to 20 class B; 19-10 class C and 10 or under class D."
The authors say the MCDA process provides a powerful means to deal with complex issues that drug misuse represents. They say: "The issue of the weightings is crucial since they affect the overall scores. The weighting process is necessarily based on judgment, so it is best done by a group of experts working to consensus."
They conclude: "Our findings lend support to previous work in the UK and the Netherlands, confirming that the present drug classification systems have little relation to the evidence of harm. They also accord with the conclusions of previous expert reports that aggressively targeting alcohol harms is a valid and necessary public health strategy."
In a linked Comment, Dr Jan van Amsterdam National Institute for Public Health and the Environment, Netherlands, and Dr Wim van den Brink, Amsterdam Institute for Addiction Research, Academic Medical Center, University of Amsterdam, Netherlands, say: "A major point not addressed in the study, because it was outside their scope, is polydrug use, which is highly prevalent among recreational drug users. Notably, the combined use of alcohol with other drugs often leads in a synergistic way to very serious adverse effects."
The Comment authors give several examples of polydrug effects. Magic mushrooms have a low incidence of adverse effects, but if consumed in combination with alcohol they have led to some fatal accidents. Other examples are the concomitant use of alcohol and cocaine leading to the highly toxic compound cocaethylene, and the extreme impairment of driving following the combined use of cannabis and alcohol
They conclude: "Nutt and colleagues' ranking of the licit and illicit drugs is certainly not definitive, because the pattern of recreational drug use is dynamic: the popularity and availability of the drugs, and the pattern of polydrug use, might change within a decade. The ranking of the drugs. should therefore be repeated at least every 5 years. Finally, for the discussion about drug classification, it is intriguing to note that the two legal drugs assessed—alcohol and tobacco—score in the upper segment of the ranking scale, indicating that legal drugs cause at least as much harm as do illegal substances."
Professor David Nutt, Imperial College London, UK, and the Independent Scientific Committee on Drugs [ICSD], London, UK. Please contact: Will McMahon ISCD T) +44 (0) 7968950223 E) Will.McMahon@crimeandjustice.org.uk or Sophie Macken T)+44 (0) 7838 119948 E) Sophie.Macken@crimeandjustice.org.uk / d.nutt@imperial.ac.uk
Wim van den Brink, Professor of Psychiatry and Addiction, Academic Medical Center University of Amsterdam Amsterdam, Netherlands T) +31(0)653700959 E) w.vandenbrink@amc.uva.nl
For full Article and Comment see: http://press.thelancet.com/tlnuttdrugharm.pdf
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Notes to editors:
*extra info from Prof Nutt: as described in the paper the weightings were decided simply by asking the group to compare harms within a subgroup of harms and then decide how they rated the relative significance of each in terms of harm – with the most important given a score of 100 and the others scaled less. The scores for the top scoring factor in each subgroup were then compared with each other and the one valued most important given a score of 100 and the other scaled less. This was then repeated for the top scoring harm for harms to person –v- harm to others. The individual scores for each drug in each harm scored less than 100 were then scaled down in proportion to their score e.g. if the group score was 80 out of 100 then scores for all drugs in that criterion were reduced by 0.8
**Quote direct from Prof Nutt and not found in text of Article
For more details on the 1 November conference, see link: http://www.drugscience.org.uk/news/
Journal
The Lancet