A new study published in the Lancet proposes that drugs should be classified by the amount of harm that they do, rather than the current A, B, and C divisions used in the UK Misuse of Drugs Act.

The new scientifically-based ranking places alcohol and tobacco amongst the most damaging of substances. These socially accepted drugs were judged to be more harmful than cannabis, and more dangerous than the Class A drugs LSD and ecstasy.

Harmful drugs are currently regulated according to classification systems that are meant to reflect the harms and risks of each drug. The scientists argue that these are generally neither specified nor transparent, which reduces confidence in their accuracy and undermines health education messages.

Professor David Nutt from the University of Bristol, Professor Colin Blakemore, Chief Executive of the Medical Research Council, and colleagues, identified three main factors that together determine the harm associated with any drug that could potentially be abused: Physical harm to the individual user caused by the drug; the tendency of the drug to induce dependence; and the effect of drug use on families, communities, and society.

Twenty drugs were then scored by an expert panel. The scores in each category Scores in each category were combined to create an overall estimate of harm and a ranking in the classification.

To provide familiar benchmarks for comparison five legal drugs, alcohol, khat, solvents, poppers and tobacco, were scored. Ketamine, a drug that has since been classified, was included in the assessment.

The process provided roughly similar scores for drug harm when used by two separate groups of experts.

Lead author Professor David Nutt said:

"Drug misuse and abuse are major health problems. Our methodology offers a systematic framework and process that could be used by national and international regulatory bodies to assess the harm of current and future drugs of abuse."

Professor Colin Blakemore added:

"Drug policy is primarily aimed at reducing the harm to individual users, their families and society. But at present there is no rational, evidence-based method for assessing the harm of drugs. We have tried to develop such a method. We hope that policy makers will note the resulting ranking of drugs differs substantially from their classification in the Misuse of Drugs Act and that alcohol and tobacco are judged more harmful than many illegal substances."

Original paper: Development of a rational scale to assess the harm of drugs of potential misuse published in the Lancet volume 369.

The Medical Research Council (MRC)