ARE YOUR DRUGS LAWS WORKING? ASK A SCIENTIST

It's pleasing to see, in the storm of commentary over Professor David
Nutt's sacking as the government's chief drugs adviser, that everyone
outside politics now recognises the importance of scientific evidence
in devising laws. But a strange reasoning twitch has appeared, in the
arguments of politicians and rightwing commentators. Science can tell
us about the molecules, they say, about their effect on the body and
the risks. But policy is separate: a matter for judgment calls on
social and ethical issues. Only politicians, they say, can determine
the correct way to send out a clear message to the public. It is not a
matter for science.

This is wrong. Alongside research into the risks of drugs, lots of
work has also been done on the deterrent impact of different laws,
classifications and levels of enforcement. As every piece of research
has its own imperfections (and nobody has yet conducted a randomised
controlled trial on drugs policy) you can make your own mind up about
whether you find the results compelling.

One strategy is to compare different countries. A World Health
Organisation study from 2008, published in the academic journal PLOS
Medicine, compared drug use and enforcement regimes around the world.
It was clear: "Globally, drug use is not distributed evenly and is not
simply related to drug policy, since countries with stringent
user-level illegal drug policies did not have lower levels of use than
countries with liberal ones."

Alternatively, you can compare drug use between states within one
country, if they have very different enforcement regimes, as when
parts of the US liberalised their laws a few decades ago.

In 1976 Stuart and colleagues found that cannabis use in Ann Arbor,
Michigan, was not affected by reductions in cannabis penalties, when
compared with three neighbouring communities which kept penalties the
same.

In 1981 Saveland & Bray looked at national drug use surveys from 1972
to 1977 and found cannabis use was higher in "decriminalised" states,
before and after changes in the law. When they looked at rates of
change, although cannabis use was increasing everywhere, the most
rapid increase was in the states with the most severe penalties.

In the same year, Johnson and colleagues used survey data on high
school use and found decriminalisation had no effect on attitudes or
beliefs about drugs. These studies are old, but only because the
liberalisations they rely on for data happened a long time ago.

Another line of evidence comes from "before and after" studies, when
laws are changed. Cannabis use in the UK dropped after cannabis was
moved from class B to class C. Prohibition of alcohol in the US from
1920 to 1933 is the most famous example: alcohol use fell dramatically
when prohibition began, and the price of alcohol rose to 318% of its
previous level. By 1929 this initial impact had begun to wear off and
rapidly: alcohol consumption had risen to 70% of pre-prohibition
levels, and was still rising when prohibition was repealed, and the
price had fallen to 171% of pre-prohibition levels. This reversion to
old patterns of use occurred despite escalating spending on
enforcement, up 600% over the same period. There are many more examples.

This is not an unresearchable question. There are other factors at
play in all of these studies, and if they are not sufficiently
rigorous for the government, or a brief informal dip into the
literature is not enough, (it shouldn't be) then they should
commission more research: because it is a tenet of evidence-based
policy that if you discover a gap, you commission work to fill it.

This work is important for one simple reason. If you wish to justify a
policy that will plainly increase the harms associated with each
individual act of drug use, by creating violent criminal gangs as
distributors, driving the sale of contaminated black market drugs,
blighting the careers of users caught by the police, criminalising
three million people, and so on, then people will reasonably expect,
as a trade-off, that you will also provide good quality evidence
showing that your policy achieves its stated aim of reducing the
overall numbers of people using drugs.