DNA faults hold key to schizophrenia

Scientists have identified three faults in human DNA that are linked with schizophrenia in a study that could open the way to a fundamental understanding of an illness that affects one in every hundred people at some time in their lives.

Until now scientists have had little insight into what goes wrong within the brain when schizophrenia is diagnosed. So identifying faults in the DNA of brain cells promises to lead to novel therapies as well as new ways of diagnosing the disease, which is probably caused by several things going wrong within the genes at the same time.

A consortium of scientists found that the three genetic mutations each confer a small but increased risk of the disorder, raising the prospect that the research could lead to a DNA test to help doctors to make earlier diagnoses.

However, the scientists dismissed the suggestion that such a test might also be used for prenatal diagnosis, or to screen IVF embryos, on the grounds that it would still not be accurate enough to indicate with a high enough probability whether a baby is likely to develop schizophrenia in late adolescence or early adulthood – the usual years when the illness first develops.

"These findings are impressive leaps towards understanding the origins of schizophrenia," said Professor Michael O'Donovan of Cardiff University, who led one of the three studies published in the journals Nature and Nature Genetics.

"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," Professor O'Donovan said.

Kari Stefansson, the chief executive of the Icelandic biotechnology company Decode, a member of the consortium, said that although the identification of the three traits is a major breakthrough, there is still much that is still not known about what causes schizophrenia.

"We are beginning the work of trying to understand a disease of the most complicated organ in our body – the brain. It is the last frontier of biology," Dr Stefansson said. "Schizophrenia is a disorder affecting thoughts and emotions. It is therefore a quintessentially human disease, but one that is little understood biologically and which is difficult to diagnose," he said.

The three mutations are all small deletions of the DNA and occur on different chromosomes. They increase the risk of schizophrenia by between three and 12 times the average risk of developing the illness, the scientists said.

They believe that further studies and identifying other genetic risk factors will soon lead to a better understanding of what triggers the disease in some people but not others.

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