HOW CANNABIS HOLDS AN UNLIKELY WAY TO TREAT SCHIZOPHRENIA

A chemical found in cannabis could be used to treat schizophrenia
with fewer side-effects than existing antipsychotic drugs, research suggests.

Though cannabis can provoke psychotic symptoms, these effects appear
to be caused chiefly by one of its components; and another compound
that damps down its effects has potential as a medicine, scientists said.

The findings, to be announced at a conference that opens in London
today, offer a possible explanation for anecdotal reports of
increasing cases of psychosis and schizophrenia triggered by the drug.

As concentrations of tetra-hydracannabinol (THC), the main
psychoactive element that can provoke psychosis, have risen, levels
of the beneficial chemical, cannabidiol (CBD) have fallen. This could
mean that users are being exposed to higher doses of the damaging
chemical, while receiving less CBD, which tends to balance THC's effects.

"There is a possibility that there are good guys and bad guys in
cannabis," said Markus Leweke, of the University of Cologne.

"THC is the bad guy, but there is a small body of literature that
suggests CBD may prevent the induction of psychotic symptoms. Our
study supports that view."

There are no official statistics on how cannabis use is affecting
levels of mental illness, but there is growing evidence that the drug
can induce psychosis and schizophrenia.

Scientists also report anecdotal evidence that more young people are
developing schizophrenia as a result of using the drug. Robin Murray
of the Institute of Psychiatry, said: "There is no robust evidence on
cannabis-induced psychosis, but there are a lot of anecdotal reports
it is increasing. Psychiatrists specialising in adolescence who used
to have no interest in psychosis are now holding clinics with lots of
patients with psychosis related to drug use."

Comparisons of US drugs seizures in the 1960s and the 1990s show that
THC levels have increased significantly as growers breed plants with
more powerful psychoactive effects, and it is known that CBD content
goes down as THC increases.

In the research, which will be presented at the Institute of
Psychiatry's international conference on cannabis and mental health,
Dr Leweke investigated the effects of CBD on 42 patients with acute
schizophrenia. Some were given CBD, while others received a standard
anti-psychotic drug called amisulpride. Both groups had fewer
psychotic symptoms, but the CBD group also experienced fewer
side-effects. Common side-effects of amisulpride include weight gain,
sexual dys-function and liver problems.

In two studies to be presented to the conference, scientists have
found new evidence linking THC to psychosis. Philip McGuire and
Zerrin Atakan, of the Institute of Psychiatry, used functional
magnetic resonance imaging to scan the brains of patients who took
THC, and found that it reduced activity in a region involved in
inhibiting inappropriate behav-iour. As activity in this region
dropped, the subjects became progressively more paranoid.

A second study, by Deepak Cyril D'Souza, of Yale University, found
that THC administered intravenously worsened the symptoms of patients
with schizophrenia.

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HIGH POINTS

The average cannabis plant contains about 60 components and 400 chemicals

Cannabidiol (CBD) is the only nonpsychoactive component; delta-9-THC
is the most psychoactive component of cannabis

The "high" is caused mainly by delta-9-THC binding to cannabinoid
receptors in the brain

About two million people in Britain smoke cannabis, and about 15
million admit to having tried it

Half of all 16 to 29-year-olds have tried it at least once

About 11 per cent of adults (13,000) and 67 per cent of 11 to
17-year-olds (9,600) admitted for drug treatment had symptoms
associated with cannabis

Sources: Royal College of Psychiatrists; University of New South Wales