MONKEY STUDY FINDS CANNABIS ADDICTIVE

Squirrel monkeys have become addicted to marijuana in laboratory
tests, according to research published today in a science magazine.
The findings will be a blow to campaigners who argue that cannabis is
non-addictive and should be legalised.

"These findings suggest that marijuana has as much potential for abuse
as drugs such as cocaine," Steven Goldberg, from the US National
Institute on Drug Abuse, reports in Nature Neuroscience.

Professor Goldberg and two colleagues at the institute in Maryland,
trained the monkeys to press a lever 10 times to inject themselves
with intravenous cocaine. When a salt solution was substituted, the
monkeys gradually stopped pressing the lever.

When the researchers replaced the salt solution with a solution of
delta-9-tetrahydrocannabinol (THC), the chemical in marijuana which
alters mood, the monkeys returned to the lever.

The monkeys gave themselves about 30 injections during a one-hour
session. Prof Goldberg's team calculated that the amount of drug
absorbed by the monkeys in an hour was - weight for weight - about the
same as that absorbed by a human adult smoking a marijuana cigarette.

Prof Goldberg said that self administration was evidence of addiction,
a theory that had been tested repeatedly since the 1950s. "It has been
used with any new drug, to see whether or not it has abuse potential.
You check it in animals before you go on to humans. Those procedures
were validated by checking virtually all psychoactive drugs. There are
virtually no exceptions. Drugs that people abuse, animals
intravenously self administer."

But until now, the exceptions have been hallucinogens used in
anti-psychotic treatments - and marijuana. There has been tentative
evidence in the past that marijuana is addictive, but campaigners have
been able to dismiss it as inconclusive, even though 100,000 in the US
each year seek treatment for marijuana dependence, and many see it as
a pathway to heroin or other drugs.

Smoking marijuana has also been found to increase fivefold the risk of
a heart attack in the first hour after inhalation.

But a huge proportion of people in Britain claims to have used
cannabis without harm. The Conservative party announced a "zero
tolerance" policy for drugs, and was embarrassed to hear seven front
benchers admit to having used the drug. There is also pressure from
doctors and researchers who are anxious to explore THC as a medical
tool.

Marijuana was widely used by doctors until earlier this century. Queen
Victoria was reputed to have been prescribed it for period pains.
There is a body of evidence that shows it can relieve glaucoma, a form
of blindness, and ease the suffering of people with multiple sclerosis.

The latest finding creates few problems for the medical lobby, who see
synthetic forms of THC as useful prescription drugs, possibly
administered in a suppository. But it challenges the argument that
marijuana is harmless.

However, the Maryland team will be criticised for using just four
monkeys in the experiment. In 1981 Prof Goldberg made the same
discovery with nicotine and tobacco prompting the US surgeon general's
report which began to undermine the tobacco industry and bring about
anti-smoking legislation - it was 10 years before other scientists
came to the same conclusions using different methods.

Prof Goldberg said: "The fact that animals did not appear to self
administer THC has frequently been used to support the idea that it is
different from other abused drugs. This is no longer true."