The Home Office insists that
cannabis "is still a controlled drug, and possession,
production and supply are still illegal", but last week, it
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
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
... 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
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?"