Friday, 23 August, 2002, 15:50 GMT 16:50 UK

'Mystery particle' in schizophrenics

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A tiny particle found in the spinal fluid of schizophrenia patients is baffling doctors who cannot work out what it is.

The Swedish researcher involved has even suggested it might be "a new form of life", although other experts say this is unlikely

However, it could mean that doctors have a reliable test for schizophrenia.

The study, led by experts at the Karolinska Institute in Stockholm, involved giving 22 schizophrenics, and 38 apparently healthy "control" patients lumbar punctures to get a sample of their cerebrospinal fluid.

Tiny spherical particles were found in the fluid from 20 of the 22 schizophrenic patients, but only two out of the 38 controls.

The study then focused on trying to work out what the particles actually were.

First a simple method of scanning for the presence of DNA - basic genetic code - failed to reveal anything.

Encouraged to grow

Then the particles were placed in a "broth" designed to encourage growth and replication.

They showed no response to this environment.

Professor Lennart Wetterburg, professor of psychiatry at Stockholm's St Goran Hospital, and one of the study's co-authors, said that more research was needed on the particles, which were bigger than viruses but smaller than normal bacteria.

However, he told Reuters: "We have viruses, bacteria and prions - this could be an entirely new form of life.

"They are more like something like the prion whcih is causing mad cow disease - but it took 15 years until it was found out what that really was."

He said it was too early to speculate whether the particles were somehow causing schizophrenia, as they could just as easily be a by-product of the illness.

Life 'unlikely'

Professor Jack Price, from the Institute of Psychiatry in London, said it was "unlikely" that the scientists had stumbled upon a new form of life.

"There is nothing to say they are alive in any way," he told BBC News Online.

"They tried to get them to replicate in a bacterial broth but this was completely unsuccessful."

He suggested that the next step might be to use more detailed tests to analyse the particles further.

He added that it was unlikely that similar experiments could be carried out here or in the US, as ethical approval for lumbar punctures on schizophrenic patients for this reason would be difficult to obtain.

The research was published in the journal Neuroscience Letters.