Pubdate: Mon, 05 Dec 2005
Source: Daily Telegraph (UK)
Copyright: 2005 Telegraph Group Limited
Contact:  http://www.telegraph.co.uk/
Details: http://www.mapinc.org/media/114
Author: Barbara Lantin
Bookmark: http://www.mapinc.org/find?207 (Cannabis - United Kingdom)
Bookmark: http://www.mapinc.org/find?232 (Chronic Pain)

CANNABIS: THE FINAL WORD

A Risk to Mental Health, or a Boon for People With MS Both, Says
Barbara Lantin

Why can't people make up their minds about cannabis? A recent issue of
a tabloid newspaper carried news of an Australian study that showed
that four out of five people with severe schizophrenia had been
regular marijuana smokers in their youth. A few pages later, it
included an article extolling the virtues of a cannabis-derived
medicine for multiple sclerosis (MS) patients.

The Home Office insists that cannabis "is still a controlled drug,
and possession, production and supply are still illegal", but last
week, it published proposals that mean anybody carrying enough to make
up to 500 joints is likely to escape trafficking charges. What are we
to make of these apparent contradictions?

The 'Good' News About Cannabis...

Last month, the Government announced that Sativex - an oral spray
derived from cannabis that is licensed in Canada but not yet in the UK
- - could be prescribed on a "named patient" basis for pain relief in
patients with MS. Sativex, which is the only medicine in the world
derived from the cannabis plant, works by influencing the way pain
messages are transmitted through the body.

"It's not that patients get high and stop caring about their pain,"
emphasises Mark Rogerson, spokesman for the manufacturers, GW
Pharmaceuticals. "A person taking a normal dose will receive only a
fraction of the tetrahydrocannabinol (THC) - the active ingredient in
cannabis that causes a high - of a recreational user."

A recent trial in the journal Neurology showed that Sativex was
significantly better than a placebo at reducing pain and sleep
disturbances in MS patients.

. and the 'Bad'

Two pieces of research published last week have added to the growing
body of evidence that, when smoked by vulnerable, young people,
cannabis can lead to serious mental illness.

A Danish study in the British Journal of Psychiatry found that almost
half of patients treated for a cannabis-related mental disorder go on
to develop a schizophrenic illness. People who had used the drug
developed schizophrenia earlier than those with the illness who had
not smoked marijuana.

The researchers emphasised that the study did not show that cannabis
caused psychosis, because factors such as heredity, other drug use and
socio-economic status had not been taken into account. However, an
American study using sophisticated imaging techniques found similar
abnormalities in the brains of adolescents with schizophrenia, and
those who use cannabis daily, but no such abnormalities in healthy
teenagers.

"These findings suggest that, in addition to interfering with normal
brain development, heavy marijuana use in adolescents may also lead to
an earlier onset of schizophrenia in individuals who are genetically
predisposed to the disorder," says Dr Sanjiv Kumra, assistant
professor of psychiatry at the Albert Einstein College of Medicine,
New York, who worked on the study.

According to Robin Murray, professor of psychiatry at the Institute of
Psychiatry in London, one person in four has the genes that make them
susceptible to developing cannabis-induced psychosis.

Are patients who take cannabis-derived drugs at risk?

"There is a distinct difference between using a drug therapeutically,
under medical supervision, and taking it recreationally," says Prof
Murray. "Cannabis is a mixture of substances; when it is used in
medicine, the aim is to have less of the hallucinogenic components,
and more of those that have an effect on muscle tension.

"Also, if you smoke a joint, you get high levels of these components
in the blood, and they decrease quite rapidly; whereas in
pharmaceutical use, you have slow absorption, and levels remain fairly
constant, so the psychotropic effects are likely to be fewer."

According to one survey, around 16 per cent of people with MS smoke
cannabis to help relieve their symptoms. However, because of their
age, this group is less likely to be at risk of schizophrenia.
"Psychosis is a disorder of youth," says Prof Murray.

According to Rogerson of GW Pharmaceuticals: "We have found no evidence that
Sativex causes psychosis. Such side effects as there are - and no drug is
without them - are generally mild, reversible and well tolerated. There may
be a temporary intoxication-like reaction, and, for this reason, we have
always excluded people with serious mental illness from our trials."

What is the Government's attitude to cannabis?

Having downgraded the drug from class-B to class-C, the Government has
asked its advisory council on the misuse of drugs to review the
possible links between cannabis and mental illness. Its report is due
by the end of the year, but leaks suggest that it will recommend no
change in the law.

"I don't care about the classification of cannabis," says Prof Murray.
"But the Government has made a major error in accompanying the
reclassification with reassurance that the drug is not harmful. What
is needed now is education. The Americans are tackling it very well.
What is our Government doing?" 
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MAP posted-by: Richard Lake