Now, new research shows such a diagnosis could be predicted as early as one year old - based on scans of infants' brains.
Using magnetic-resonance imaging scans, researchers at the University of North Carolina were able to predict - with an 80 percent accuracy rate - which babies who had an older sibling with autism would be later diagnosed with the disorder. Researchers believe that the brain changes underlying ASD begin much earlier - possibly even in the womb.
Using data gathered from the study, the researchers also hope to determine how certain environmental factors such exposure to toxic metals and air pollution can influence the likelihood of a baby to develop autism.
A new study has focused on the early diagnosis of autism. Also, the approach was almost ideal in predicting which high-risk babies would not develop ASD by age 2.
A team of researchers has shown that measuring the growth of brains in babies can predict the onset of autism later in childhood. But behavioural assessments haven't been helpful in predicting who will get autism, says Joseph Piven, a psychiatrist at the University of North Carolina (UNC) in Chapel Hill, who co-led the study, published online in Nature. In the general population in the USA, autism is diagnosed in about one in 68.
The overgrowth of the brain coincided with the behaviors typical of autism that start to emerge in the second year. Although only useful for high-risk infants, the findings may eventually lead to diagnostic innovations.
"We haven't had a way to detect the biomarkers of autism before the condition sets in and symptoms develop", Piven said in a statement.
"These findings not only are significant for the field of autism, but they also could inform the broader field of psychiatry and prevention science as it relates to various psychiatric conditions", Elison said. Of the high-risk infants, 15 presented with brain overgrowth went on to develop autism by their 24th month.
Mandy Williams, CEO of the charity Child Autism UK, said: "Potentially, the earlier you can diagnose autism the better". A large follow-up study would be needed to test whether autism can be predicted in the general population, she says.
This is possible for babies with older autistic siblings, as reported by the University of Minnesota. Other key collaborators are McGill University, the University of Alberta, the College of Charleston, and New York University.
By giving researchers a potential tool to diagnose babies, Dawson says the new study could open up possibilities for testing the potential new therapies. That change happened before the child's first birthday. But children in groups with higher rates of autism - like those who have affected siblings or who carry genes linked to autism - might benefit the most from it. In addition, its unique family-centered care and public service programs have brought the 535-bed hospital recognition as a leading advocate for children and adolescents.