Symptoms of autism such as poor eye contact and limited communication skills are not noticeable during a baby’s first months of life, but appear gradually as children approach their first birthday, according to new research.

The conclusion published online Tuesday is significant as doctors and researchers look for more accurate methods to identify children with autism as young as possible in order provide early intervention.

“Contrary to what we used to think, the behavioral signs of autism appear later in the first year of life for most children with autism. Most babies are born looking relatively normal in terms of their social abilities but then, through a process of gradual decline in social responsiveness, the symptoms of autism begin to emerge between 6 and 12 months of age,” said the study’s lead author Sally Ozonoff of the University of California, Davis M.I.N.D. Institute.

Ozonoff and her colleagues looked at two groups of children, half of whom have siblings with autism and were considered “high-risk” and half of whom had no family members with autism and were considered “low-risk.” Both groups were monitored until age 3.

Unlike previous studies which relied on parent recollections of the first signs of autism, researchers intensely observed children’s behaviors during lab visits.

After six months, “the autism spectrum disorder group showed a rapid decline in eye contact, social smiling and examiner-rated social responsiveness,” the researchers report in findings published online ahead of the March issue of the Journal of the American Academy of Child & Adolescent Psychiatry.

Differences in the two groups continued to manifest into the second and third years of life, leading researchers to suggest that doctors may need to continue autism screenings into age 3. Currently, doctors are advised to screen twice for the disorder before children turn 3.

“We need to be careful about how we screen and we need to know what we’re looking for,” Ozonoff said. “This study tells us that screening for autism early in the first year of life probably is not going to be successful because there isn’t going to be anything to notice. It also tells us that we should be focusing on social behaviors in our screening since that is what declines early in life.”

Read more stories like this one. Sign up for Disability Scoop's free email newsletter to get the latest developmental disability news sent straight to your inbox.