SCANS REVEAL BRAIN DAMAGE FROM CANNABIS IS LIKE SCHIZOPHRENIA

SCIENTISTS have shown for the first time that the damage to brains
from smoking cannabis is the same as that in schizophrenia sufferers.

Images taken using a new scanning technique provide evidence that
cannabis disrupts the brain's electrical signals in the same way as
in schizophrenia.

The findings add to growing evidence the drug may be a significant
cause of mental illness in adolescents and a possible trigger for
schizophrenia in those who are genetically vulnerable.

Previous studies have examined patients' behaviour and medical
histories. This is the first time direct evidence of a link has been
found inside the brain.

"What we saw should cause alarm because the type of damage in
cannabis smokers' brains was exactly the same as in those with
schizophrenia and in exactly the same place in the brain," said Dr
Manzar Ashtari, associate professor of radiology at the Albert
Einstein College of Medicine in New York. Her research was presented
last week to the Radiological Society of North America in Chicago.

Ashtari added: "To me, this is proof of the damage cannabis can do
and it is shown up graphically for the first time. All the research
by psychiatrists so far has strongly suggested cannabis-smoking
youngsters run a higher risk of developing psychotic behaviour. Now
we have extremely strong evidence that shows what damage has been done."

The new research will add to pressure on the government to change its
policy on cannabis. Last year the drug was downgraded from class B to
class C, which means the police no longer routinely arrest people
caught with small amounts.

The Advisory Council on the Misuse of Drugs is shortly expected to
tell Charles Clarke, the home secretary, that evidence of the harm
caused by cannabis is not strong enough for this decision to be reconsidered.

Ashtari's team used a new technique called diffusion tensor imaging
to look into the brains of 15 cannabis smokers, who had all given up
taking the drug a month before the study.

They had smoked an average of once a day for a year and were aged 15
to 18. Their brains were compared with those of schizophrenics and of
healthy people.

The scans looked deep into the "white matter" -- the material that
connects brain cells. In patients with schizophrenia, electrical
signals are no longer routed correctly.

Schizophrenia sufferers find they are unable to separate real from
unreal experiences and may see hallucinations, hear voices, lose the
ability to concentrate and become paranoid. Sufferers typically
develop the illness between the ages of 17 and 30.

In both the schizophrenia patients and the cannabis users, damage was
found to white matter in a bundle of nerves and other fibres in the
left frontal lobe. This area is associated with language and hearing.

This part of the brain is still developing during adolescence, which
means it is vulnerable to damage. "We were able to see in real time
abnormal behaviour in this area which was not present in the brains
of adolescents who did not have schizophrenia and had not smoked
cannabis," said Ashtari.

Robin Murray, a professor at the Institute of Psychiatry in London,
said: "This does seem to be a landmark study, although we will need
to see it repeated. For the first time, we are able to see the
effects of cannabis smoking on the brain."