Three independent studies have identified gene variants which contribute significantly to schizophrenia risk, taking steps towards understanding the cause of this highly complex condition which affects 1 in 100 people. Two of the three gene variants discovered were rare, but conferred 12 and 15 percent higher risks, while the third was more common, but carried a much lower risk.

Although encouraging, the gene discoveries are unlikely to lead to a genetic test for predicting schizophrenia risk in the near future, Professor Michael O'Donovan of Cardiff University, who led one of the studies, told the Independent. 'These findings are impressive leaps towards understanding the origins of schizophrenia,' he said, 'but since only a small amount of the genetic risk of schizophrenia has been accounted for, they are not ready to be applied to genetic testing, an area that has seen fierce controversy as a number of biotech companies have begun offering genetic tests for psychiatric disorders'.

After scanning the genomes of thousands of people with schizophrenia and comparing it to that of healthy volunteers, two of the groups independently discovered the same two rare gene variants, which occurred up to 15 times more frequently in people with schizophrenia than those without. The findings support previous studies suggesting that rare genetic variants play a much bigger part in schizophrenia than common ones.

Most researchers agree that schizophrenia results from complex interactions between both environmental and genetic influences, leading some commentators to say that more should be done to identify and limit environmental causes, before trying to tackle genetic ones. 'There is lots you can do - it's half nature, and half nurture, and we have good evidence for many of these things. 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,' said Jane Harris, from the mental health charity Rethink, speaking to the BBC.

More than 100 groups are working together to pool data as part of the International Schizophrenia Consortium. It is anticipated that future studies will examine even larger groups of people.