Pubdate: Tue, 01 May 2007
Source: Times, The (UK)
Copyright: 2007 Times Newspapers Ltd
Author: Mark Henderson, Science Editor


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.



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 
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