Children who develop autism have significant differences in the development of their brains, evident as early as six months of age, researchers have determined.

Health experts said the new study of high-risk infants who later develop autism could help improve techniques for diagnosing the condition early and getting intensive treatment and education for such children that can make a significant difference.

The study by the Infant Brain Imaging Network -- including researchers at the Center for Autism Research at the Children's Hospital of Philadelphia -- suggests that autism does not appear suddenly in young children but instead develops over time during infancy.

Sarah Paterson, at Children’s Hospital Center for Autism Research, called the findings “a very important first step towards identifying a biomarker for autism risk.”

She added: "This research raises the possibility that we might be able to intervene even before a child is 6 months old, to blunt or prevent the development of some autism symptoms."

The study, published in the American Journal of Psychiatry, involved 92 infants considered at high risk for autism, because they all have older siblings with the disorder. Each child’s brain was scanned using an MRI at 6 months and behavioral assessments were performed at 24 months. At 24 months, 28 of the infants were deemed to have autism. The children with autism had differences in brain features known as “white matter fiber tracts” – pathways that connect brain regions – compared to the non-autistic children.

These developmental differences may suggest children with autism have slower white matter development during early childhood, when the brain is making and strengthening vital connections.