IF THERE is one thing that politicians can and should do to limit the damage caused by illegal drugs, it is to take careful note of the evidence and develop a rational drug policy. Some politicians find it easier to ignore the evidence, and pander to public prejudice instead.

I can trace the beginning of the end of my role as chairman of the UK鈥檚 official advisory body on drugs to the moment I quoted a 快猫短视频 editorial (14 February, p 5). Entitled, fittingly enough, 鈥淒rugs drive politicians out of their minds鈥�, the editorial asked the reader to imagine being seated at a table with two bowls, one containing peanuts, the other the illegal drug MDMA (ecstasy). Which is safer to give to a stranger? Why, the ecstasy of course.

I quoted these words in the at King鈥檚 College London in July. This example plus other comments I have made聽鈥� such as horse riding is more harmful than ecstasy聽鈥� prompted Alan Johnson, the home secretary, to say that I had crossed the line from science to policy. This, he said, is why I had to go.

But simple, accurate and understandable statements of scientific fact are precisely what the advisory council is supposed to provide. Why would any scientist take up some future offer of a government advisory post when their advice can be treated with such disdain?

As well as ignoring its own advisers, the UK is falling out of step with international trends. When Portugal softened its drugs laws in 2001, drug use remained roughly constant, but ill health and deaths from drug taking fell. Decriminalisation quietly crept up the agenda in Vienna this year at a meeting of the UN Commission on Narcotic Drugs, where governments heard new, independent evidence on how the harms of criminalisation were outweighing the benefits. In August, decriminalising possession of small amounts of marijuana and other drugs. And just last month, Eric Holder, the US attorney general, instructed federal prosecutors to in the 14 states where such use is legal.

No one doubts that heavy users of marijuana are risking trouble with their mental health. What I have simply pointed out is that we need a consistent policy, recognising that heavy users of alcohol and tobacco are more numerous and are causing themselves聽鈥� and others 鈥� even more trouble through their indulgence.

Policies that ignore the realities of the world we live in are doomed to fail. This is true for just about all the biggest issues that we confront, from energy and climate to criminal justice, health and immigration. I鈥檓 not arguing that science dictate policy; considerations such as cost, practicality and morality also have a role. But scientific evidence should never be brushed aside from the political debate.

The current British government has said repeatedly that it wants its policies to be evidence-based, but actions speak louder than words. On ecstasy, for example, it made policy first, sought advice second 鈥� and cynically rejected the advice it was given. The result is shambolic policy-making which gives great cause for concern if that is how governments operate more generally.

The results of a government inventing its own reality and acting on it can be seen in the appalling consequences the George W. Bush presidency had for world peace, the environment and human rights. The message for the British government is a simple one: don鈥檛 exclude rational argument in order to exploit a visceral public response. Politicians have to win the hearts and minds of their electorate. If your policy is informed by an underlying moral imperative, be open about what that is, and don鈥檛 try to disguise it with a veneer of pseudo-science. We ignore scientific evidence at our peril.

But perhaps the most important aspect of Opium: A History (Simon
& Schuster, 拢17.99, ISBN 0 684 81686 5) is the light it throws on the
modern legalisation debate. In his detailed account of the origins of the
control of opiates in the 19th century, Booth points out that opium in various
forms was freely available and widely used in all levels of society. People were
exposed to the drug early in life since one of its most popular applications was
as a means of keeping babies quiet.

At the time, opium was perceived by some as less problematic than tobacco.
But many adults and children died of overdose and as the lasting agony of
dependence was recognised, prohibition was gradually introduced.

At several times in its history opium was made legal and actively marketed in
China鈥攂y the British for commercial gain and by the Japanese as an agent
of social control. Both instances saw high levels of dependence, with over 10
per cent of the population becoming seriously addicted.

The only major omission in Booth鈥檚 book is a discussion of the brain
substrates on which opium acts, especially the brain鈥檚 own opiate
neurotransmitters. Nevertheless, this is an impressive and scholarly book that
is immensely readable, highly informative and makes a timely and balanced
contribution to the current debate on how we deal with the growing problem of
opiate abuse.