Lifestyle and exercise

Study compares drug harms

“Alcohol is more harmful than crack or heroin,” reported The Daily Telegraph and many other newspapers today. The headlines stemmed from a study published in The Lancet medical journal by Professor David J Nutt, the former head of the Advisory Council on the Misuse of Drugs. Professor Nutt was asked to resign last year by the former home secretary for making similar claims.

The Lancet analysis ranked 20 drugs according to harms attributed to them by Nutt and other experts in a “one day interactive workshop”. Not surprisingly, perhaps, heroin, crack cocaine and metamfetamine were found to be most harmful to individual users. They also led the list of illegal drugs most harmful to society and others. However, because alcohol is legal and most widely available, it was found to be most harmful overall.

The researchers have used a valid technique commonly used in policy making. However, the findings say little about the potential dangers of drugs like crack and heroin because their supply is severely limited and they are not as widely used as alcohol.

Overall, this is a well-conducted analysis of a complex policy area and a reminder that alcohol misuse causes widespread social harm. Outside of this context its usefulness is limited.

Where did the story come from?

The study was carried out by Professor David J Nutt from Imperial College London, Leslie A King, the UK Expert Adviser to the European Monitoring Centre for Drugs and Drug Addiction, and Lawrence D Phillips from the London School of Economics and Political Science.

The researchers report the results of a consultation exercise and analysis carried out by the UK Advisory Council on the Misuse of Drugs and the Independent Scientific Committee on Drugs (ISCD). The ISCD is an independent group founded to review the scientific evidence relating to drugs. The group is chaired by Professor Nutt.

Funding was provided by the Centre for Crime and Justice Studies. The study was published in the peer-reviewed medical journal The Lancet.

This research has received widespread coverage in the media, in which its context and policy implications are also discussed. However, many news sources fail to discuss the details of what the study involved or any of its limitations.

What kind of research was this?

The aim of this research was to assess and compare various harms associated with 20 recreational drugs in the UK. The researchers say that it is important for policy makers in health, policing and social care to have good guidance on the harms of drugs. Here, they wanted to improve on previous reviews of drug harms by applying a formal framework to the process.

To do this, the research team used a technique called a multicriteria decision analysis (MCDA). This is a commonly used analytical tool in the policy area, and the researchers say that it has been successfully used to aid decision makers “facing complex issues characterised by many, conflicting objectives - eg, appraisal of policies for disposal of nuclear waste”.

Essentially, this MCDA involved groups of experts in the drug policy-making area, who rated the harms to both individuals and to communities associated with 20 legal and illegal substances. These included alcohol and tobacco, and drugs such as heroin, crack cocaine, cocaine, amfetamines and cannabis.

In an open discussion, they then scored the drugs according to 16 criteria of harm: nine harms related to the individual (such as health, death, relationships) and seven related to harms to others (such as crime and costs to the economy and community). The group then assessed the relative importance of the criteria to produce a ‘score’ for each drug, for harms to the individual, others and a combination of the two.

What did the research involve?

There are several different approaches to multicriteria decision analysis, and the specific details of the analysis depend on the context in which decisions are being made. In this analysis, experts and specialists from the UK Advisory Council on the Misuse of Drugs met in 2009 to derive a list of 16 harm criteria that are associated with drug use, nine of which relate to harms to an individual and seven to others (both in the UK and internationally).

The harms to the individual were:

  • drug-specific mortality
  • drug-related mortality
  • drug-specific damage
  • drug-related damage
  • dependence
  • drug-specific impairment of mental functioning
  • drug-related impairment of mental functioning
  • loss of tangibles (income, housing, job etc)
  • loss of relationships

The harms to others were:

  • injury
  • crime
  • environmental damage
  • family adversities
  • international damage
  • economic cost
  • community

At a second meeting, lasting a day, experts from the Independent Scientific Committee on Drugs scored each drug on the 16 harm criteria and then discussed the importance of each of these criteria and the definitions that the previous group had produced. The meeting was facilitated by an expert in the process of decision analysis, which the researchers say enabled them to “work effectively as a team” and “enhance their capability to perform”.

During this process, each drug was given a score out of 100 (with 100 being the most harmful) on each of the 16 criteria. Each criterion was also assigned a weight according to how important that criterion was in the context of the UK. Each of the drug scores was then multiplied by this weighting to arrive at a weighted harm score for individual drugs.

The details of the MCDA process were published in The Lancet along with a discussion of how the results relate to UK policy, providing a ranking of the harms of different drugs/substances to individuals and to the community.

What were the basic results?

When the individual harm and the harm to others scores were combined, alcohol was the most harmful drug, scoring 72 out of 100. This was followed by heroin (55) and crack cocaine (54).

These were also the three most harmful drugs to others: alcohol (46), heroin (21) and crack cocaine (17).

Crack cocaine (37), heroin (34) and metamfetamine (32) were considered the most harmful to individual users, in that order.

How did the researchers interpret the results?

The authors say that the MCDA process provides a “powerful means to deal with complex issues that drug misuse presents”. They conclude that their analysis confirms that the “present drug classification system has little relation to the evidence of harm” and highlights the importance of targeting alcohol harms as part of a public health strategy.


The researchers have applied a valid technique that is commonly used in policy making where there is a need to consider many, often conflicting, factors. The findings may be of interest to policy and decision makers, and go some way towards estimating the contribution of different drugs to societal harms. However, the results are not of much use beyond this point. Not surprisingly, alcohol, which is legal and popular, is associated with the greatest overall harms. Its impact on society is large because it is widely used.

The researchers had to rate how harmful they believed each of these drugs to be according to various criteria. As such, it is unavoidable that there is subjectivity in deciding how these harm criteria are weighted. The composition of the expert group convened for this exercise is critical to the outcome, and it is possible that other experts with different opinions could reach different conclusions. How the group weighted individual compared with societal harms is a key determinant of the overall score.

The researchers highlighted the following limitations to their approach:

  • They only considered harms, and say that some drugs do have benefits that may offset some harms (for example, the commercial benefits to society of the tobacco and alcohol industries).
  • They note that their results may not be relevant to countries with different legal and cultural systems to the UK.
  • They did not include prescription drugs.
  • They did not investigate the harms associated with use of more than one drug or substance (for example, alcohol plus recreational drugs).

For individuals wanting a bottom line about the harms of drug use, the finding that heroin, crack cocaine and metamfetamine were most harmful to individual users is important. Policy makers are interested in overall harms or the harms to society and the methods to quantify these will always have some element of subjectivity and will, therefore, always be controversial. The researchers have attempted to put numbers to the wider impact of different drugs, but the fact remains that alcohol tops the list of overall harms largely because it is a legal, widely used drug.

NHS Attribution