Page last updated at 17:09 GMT, Wednesday, 30 July 2008 18:09 UK

Gene flaws link to schizophrenia

Human DNA
Many genes are thought to play a role in schizophrenia

Three separate research projects have pinpointed genetic flaws linked to schizophrenia.

One of these, reported in the journal Nature, could mean a fifteen-fold increase in risk.

However, one of the researchers warned that schizophrenia is so complex genes alone will only ever partially explain the illness at best.

Mental health charities said genetic studies should be matched by work to reduce the known risk factors.

It's very dangerous to say never, but to me, there are so many genes involved, that the idea of predicting whether someone will develop schizophrenia doesn't seem to me very likely
Professor Michael O'Donovan
Cardiff University School of Medicine

Scientists have suggested that an individual's risk of schizophrenia is roughly half dictated by their genetic make-up, and half by other factors during their lives.

However, on both sides of this equation, much has still to be revealed about the precise causes.

The three large-scale projects have taken a step towards unravelling the genetic picture of schizophrenia.

Two separate international groups, both testing thousands of people with schizophrenia and healthy volunteers, identified the same two rare genetic variants which appeared to contribute strongly to the chances of developing the disease.

However, although one of them increased the risk 12 times, and the other 15 times, they are carried by relatively few people, and so cannot play a part in a large proportion of schizophrenia cases.

The third group, led by Professor Michael O'Donovan, from the University of Cardiff Medical School, and published in the journal Nature Genetics, revealed more common genetic variations, held by many larger numbers of people, but which offer a much smaller contribution to their risk of schizophrenia.

Professor O'Donovan said that while the research was an important step - and could eventually lead to greater understanding, or even better treatment, for schizophrenia, scientists were still far from having a complete picture of how various genetic flaws might work together or separately to produce schizophrenia symptoms.

He said: "It's very dangerous to say never, but to me, there are so many genes involved, that the idea of predicting whether someone will develop schizophrenia doesn't seem to me very likely."

He said it was possible that further study would uncover many different genetic "routes" to schizophrenia symptoms.

Caution call

Jane Harris, from the mental health charity Rethink, welcomed the advance, but urged people to focus on aspects they could change to reduce the risk of schizophrenia.

She said: "There is lots you can do - it's half nature, and half nurture, and we have good evidence for many of these things.

"We know, for example, that obstetric complications, or cannabis use, have been linked with an increased risk of schizophrenia.

"Genetics is just a really grey area, and there is a danger people will think you can predict it, or even pretty much eliminate it."

Marjorie Wallace, from Sane, said that research was important, as it could eventually shed more light on those at greater risk.

But she added: "However, these findings should be treated with caution, as they may be adding to the confusion in a world where scientific studies into the genetic cause or causes of schizophrenia have to date yielded many false positives and led down many cul-de-sacs."

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