The largest study into the genetic source of autism has pinpointed two links that may predispose children to develop the condition.

Scientists and charities said the discovery should lead to a better understanding of the complex brain disorder and could eventually lead to a cure.

Autism affects an estimated 50,000 people in Scotland, with sufferers experiencing difficulties forming social relationships, problems with communication and the development of obsessions.

There is growing evidence to suggest that genetic factors are responsible for some forms of autism and scientists have spent years trying to identify the genes.

More than 120 experts from 19 countries are working on the Autism Genome Project (AGP), the most ambitious of its kind, which involves studying nearly 1200 families with two or more members suffering from autism.

Their preliminary results, published today, show that a previously unidentified region of chromosome 11 could be linked to the disorder. The research also reveals a gene called neurexin 1 could be implicated.

Neurexin 1 is a member of a family of genes which allow neurons (brain cells) to connect and communicate. Thus, mutations in neurexin 1 could play a critical role in autism spectrum disorders.

The study was led in the UK by Professor Jonathan Green, a child psychiatrist, at Manchester University.

He said: "We hope these exciting results may represent a step on the way to further new treatments in the future.

"Autism is a very difficult condition for families - communication is taken for granted by parents of healthy children but is so greatly missed by those with autistic children.

"We are working now in Manchester to investigate the basic science and develop and test new treatments."

Carol Evans, director of the National Autistic Society Scotland, said the charity followed the new research with great interest.

"NAS Scotland welcomes all studies which further our understanding of autism. Research into the genetic causes of autism is ongoing but the potential benefits for diagnosis and treatment are still many years away."

There has been speculation in the media that autism can be triggered by environmental factors, including toxic heavy metals, or watching television.

But most scientists agree the underlying cause is likely, in most cases, to be genetic.

AGP researchers used two techniques to examine the DNA of the families with a history of autism. So-called "gene chip" technologies were used to look for genetic similarities among affected families.

In addition, scientists scanned DNA for anomalies which might contribute to risk for autism - or could even cause it in rare cases.

They found a number of variations in the genetic material of people with autism, adding to the evidence that tiny, rare variations in genes may heighten the risk for autism spectrum disorders.

Their study is published today in the journal Nature Genetics.