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."