There's a story on the BBC radio and website about a paper in The Lancet reporting a new classification of illegal drugs, along with alcohol and tobacco. They find that according to their classification scheme alcohol is more destructive than any of the illegal drugs, including heroin and crack cocaine.
The authors of the paper applied "multicriteria decision analysis" (MCDA) to the problem -- sounds scientific, doesn't it? (Indeed, there's a whole journal of MCDA; the idea is to allow decision makers to apply 'scientifically sound' criteria to policy decisions that are otherwise essentially subjective.)
Members of the Independent Scientific Committee on Drugs, including two invited specialists, met in a 1-day interactive workshop to score 20 drugs on 16 criteria: nine related to the harms that a drug produces in the individual and seven to the harms to others. Drugs were scored out of 100 points, and the criteria were weighted to indicate their relative importance.
MCDA modelling showed that heroin, crack cocaine, and metamphetamine were the most harmful drugs to individuals (part scores 34, 37, and 32, respectively), whereas alcohol, heroin, and crack cocaine were 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.This is an interesting conclusion in its own right, and the issues of prohibition and legalization have been widely discussed on the BBC and elsewhere as a result because the harmfulness of alcohol is largely due to its legal and thus widespread use compared with illegal substances. But this also tells us something about the limitations of science as it pertains to policy decisions. The authors of the study recognize upfront that there is much subjectivity in the assessment of 'harm' and 'danger' and have tried to at least take that into account in their classification scheme using MCDA. But, the measures are still subjective, and that undermines their 'scientific' nature, to say the least.
More importantly, the results will be ignored. Policy decisions about drug legalization will still be political. We learned long ago that we cannot successfully ban alcohol from society. We are not yet to the stage where even marijuana can be widely legitimized. No matter what the science says, we won't ban alcohol, you can bet your beer on it. And despite attempts to stifle it, there is no sign that we have the gumption to ban tobacco (nor, according to a great many people who smoke, sniff, or chew, would that be in any way justified so long as the only harm is self-directed).
Similarly, matter what the science says, we simply are not going to legalize all recreational drugs. Why? This is a cultural view, not one about the facts. We won't, at least not in the US and Britain. No matter how much damage the drug lords in Mexico or Afghanistan or Colombia cause to our own population. No matter that it is our usage here in the US and Europe that is responsible for the trade. We are not going to legalize it, even if it's as harmless as a baby's smile (it isn't, of course). Culture will have to lead any such change.