30/04/2007 16:00:00
UK: Cannabis chemical curbs psychotic symptoms, study finds
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One of the active chemicals in cannabis inhibits psychotic symptoms in
people with schizophrenia, according to a study which compared it with a
leading anti-psychotic drug. Although the finding could lead to new
treatments for schizophrenia, scientists think it may also explain why
cases of cannabis-induced psychosis are apparently on the rise.
Most cannabis research focuses on tetrahydrocannabinol (THC), the active
ingredient that produces the high. Recent studies have shown THC makes
symptoms of schizophrenia worse and triggers the condition in a small
proportion of users.
But the new research shows that another chemical, cannabidiol (CBD), has
the opposite effect. "One possibility is that there are good guys and
bad guys within cannabis," said Markus Leweke, of the University of
Cologne. He and his team compared the effects of CBD and a leading
anti-psychotic drug, Amisulpride, on 42 patients with schizophrenia.
After four weeks the symptoms of both groups had improved, but those
treated with CBD suffered fewer side-effects.
"Maybe the cannabidiol ameliorates some of the effects of the THC and
maybe it actually might be good for you if you are psychotic," said
Robin Murray, of the Institute of Psychiatry at King's College London.
They reported their research at the second International Cannabis and
Mental Health Conference in London.
There is anecdotal evidence that the number of patients in the UK with
psychotic symptoms linked to cannabis use is increasing. Professor
Murray speculated that this may be linked to the increased THC content
of herbal cannabis sold on the street. Cannabis on sale today has
roughly doubled in strength in the last decade.
In a second set of experiments, researchers at the Institute of
Psychiatry have shown how THC acts on the brain to induce paranoia. "By
using brain scanning you can look in real time at the effect of the
different components of the cannabis on healthy people and see how it's
affecting the healthy brain," said Philip McGuire, a brain imaging
expert at King's College London.
The team gave subjects a dose of THC or a placebo and then observed
which areas of the brain were active while they performed a computer
task that involved stopping certain movements. All volunteers were
healthy men between 20 and 40 who had used the drug fewer than 15 times.
By looking at the difference in brain activity between placebo and THC
groups, the researchers identified a region that is involved in
controlling inappropriate behaviour. Those with the biggest reduction in
the activity of that brain region also experienced more paranoid symptoms.
"One possible interpretation of that is the paranoia is being driven by
interfering with this area of the brain," said Professor McGuire.
http://www.guardian.co.uk/drugs/Story/0,,2069281,00.html
Source:
http://www.ukcia.org/news/shownewsarticle.php?articleid=12499
Author:
The Guardian via UKCIA
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