Scientists have identified a genetic pattern common to people with autism that is linked to the way messages are sent in the brain.
Medical Research Council (MRC) researchers at the University of Oxford said the knowledge could help them understand the role that genetics plays in autism.
Doctors can currently only identify the exact genetic cause of autism in about one in five cases but it is known that genes play an important role in the development of autism spectrum disorders, an MRC spokeswoman said.
A total of 181 autism patients who either had additional copies of some genes, or fewer copies, than those without autism were studied by the team at the MRC's functional genetics unit.
The researchers found that in about half the patients, the affected genes worked together as part of a biological network involved in the way information passes between brain cells.
Dr Caleb Webber, lead author of the study, said: "Think of a pipe that carries water. At some points along the pipe there are genes that act as taps to let more water into the pipe.
"At other points genes act as holes to let some of the water out. We found that in individuals with autism the mutations in all these different types of genes act in the same way to affect water flow.
"This indicates the 'tap' genes are duplicated in some individuals with autism which increases flow into the pipe, while in other individuals with autism the 'hole' genes are deleted which decreases the amount of water leaving the pipe.
"Both of these events cause the same thing - too much water flowing through the pipe.
"Knowing not just which 'pipes' in the cell are affected in autism but also in what way they are affected helps us to know in which way we have to change the flow to restore the balance."
Autism spectrum disorders affect about 1 per cent of the population and affect social interaction, communication and repetitive behaviour.
The study is published in the journal PLOS Genetics.
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