MARIJUANA STILL BEFUDDLES LAW-MAKERS

TWO conflicting reports on the effects of cannabis seem set to push the
drugs policies of the US and Canada in opposite directions.

The Canadian Senate Special Committee on Illegal Drugs will release a
report this week that is expected to recommend consideration of some form
of legalisation. The committee has already produced a discussion paper
stating that there is no convincing evidence that using cannabis makes
people more likely to abuse harder drugs.

The committee points out that of loo adolescent users, just 10 will
continue to use the drug regularly into adulthood and 5 will progress to
other drugs. It also suggests that criminal sentences may be the most
damaging result of marijuana use.

In stark contrast, a report released last week by the US Substance Abuse
and Mental Health Services Administration, based on annual surveys, says
that the younger children are when they first use marijuana, the more
likely they are to use cocaine and heroin and become dependent on drugs as
adults. It concludes that postponing people's first use could prevent
progression to other illicit drugs.

"These findings are of grave concern because studies show smoking marijuana
leads to changes in the brain similar to those caused by cocaine, heroin
and alcohol," says Charles Curie of the administration. "Heavy marijuana
abuse impairs the ability of young people to retain information during
their peak learning years when their brains are still developing."

Decriminalisation will make cannabis more available, more acceptable and
cheaper, adds David Murray of the White House Office of National Drug
Control Policy, making it more likely that younger people will try it.

"Decriminalisation of marijuana, I believe, is not only weak drug policy,
it is from a public health perspective a deep mistake," he says.

The US report has been met with scepticism from many researchers, who point
out that a statistical correlation does not prove the physiological
"gateway" hypothesis that cannabis use leads to harder drugs. Nor does it
prove that preventing cannabis use will reduce the risk of later drugs
problems. "It's embarrassing that officials are still spouting this
nonsense," says Mitchell Earleywine of the University of Southern
California, author of Understanding Marijuana.

The only evidence for brain differences is that people who start taking
marijuana before age 17 or so have less grey matter, he says. But it's
impossible to know whether this is a result of drug use or a reason why
they took up the drug. "They are picking out evidence that suits the
political agenda rather than being truly objective," he says.

The report also shows that 91 per cent of marijuana smokers had previously
used alcohol or cigarettes. "Whatever's most available gets used first,"
says Earleywine. "That maybe a more parsimonious explanation for the
staging of drug use than anything else."

The Canadian and the US studies do agree on one thing: drug policies make
little difference to the number of people who try the drug - around 45 per
cent of young adults. "That should be the real headline," says Bruce Mirken
of the Marijuana Policy Project in the US, which advocates policies aimed
at minimising any harmful effects.