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updated 11/8/2010 1:31:24 PM ET 2010-11-08T18:31:24

People who possess a specific change in one of their chromosomes are nearly 14 times more likely to develop an autism spectrum disorder or schizophrenia than those without this change, according to a new study.

The change, which is called a deletion, happens when a section of chromosome 17 is missing. The deletion is found only in people who have an autism spectrum disorder, a developmental delay or schizophrenia, said study researcher David H. Ledbetter, a genetics professor at Emory University.

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"This is just adding one more to that rapidly growing list of genetic mutations" associated with autism that doctors could use to measure autism and schizophrenia risk in children, Ledbetter told MyHealthNewsDaily.

Not all people with autism, a developmental delay or schizophrenia have this deletion. But all people who have the chromosome change will develop some form of the disorders, whether it's mild or strong enough for a diagnosis, he said.

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Schizophrenia and autism are separate disorders, but other recent research has also shown the two have genetic similarities.

"At least in a subset of autism and a subset of schizophrenia, the same [genetic changes] play a major role in both," Ledbetter said. "It will be interesting in the future, because we'll have the ability to identify this type of deletion in young children, and follow them to figure out why some of them do develop autism and some don't."

The new study was published today (Nov. 4) in the American Journal of Human Genetics.

Detecting the deletion

Researchers looked in a genetic database of 15,749 people with a developmental delay, intellectual disability or an autism spectrum disorder.

They found 18 of these people had the deletion on chromosome 17. But not one of the 4,519 healthy people tested had the deletion, according to the study.

Researchers tracked down nine of the 18 people in the database with the genetic deletion. All nine had cognitive impairments, and six of them had autism, the study said.

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To confirm these findings, researchers looked at two other databases that had genetic information for 7,522 people with autism or schizophrenia. They found the same deletion in two people with an autism spectrum disorder or cognitive impairment, and four adults with schizophrenia. None of the 43,076 healthy people tested had the deletion.

"That means the deletion has a major phenotypic effect," Ledbetter said. "It can manifest as developmental delay, intellectual disability or autism, or it may not be diagnosed and recognized until adulthood when there are psychiatric manifestations that lead to a diagnosis of schizophrenia."

In line with the research

Some of the people with the deletion also had other health problems, such as renal cysts and diabetes.

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"We're starting to appreciate now that oftentimes, when we talk about psychiatric conditions, it doesn't really come just by itself," said Andy Shih, vice president of science for the nonprofit Autism Speaks, who wasn't involved with the study. "A lot of times, you see a host of other conditions that travels with autism."

Previous work has found genes that are associated with autism, but these genes have "low penetrance" – meaning the genes were also found in people who don’t have any symptoms of autism, said Patricia Rodier, a professor at the University of Rochester School of Medicine and Dentistry.

"But in this case, it appears that virtually all of the people who have this anomaly of this gene have some symptoms," said Rodier, who wasn't involved with the study.

The new findings could be used in a genetic test that could help people confirm an autism or schizophrenia diagnosis, as well as determine their risk of developing one of these conditions, Rodier said.

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