New research indicates that the signs of autism cannot be spotted in babies before they're six months old, but do start emerging by the time they reach their first birthday.
This study suggests that looking for early signs of autism in young babies is probably of no use.
The siblings of children already diagnosed with autism are known to be at greatest risk of developing the disorder. For that reason, parents of autistic children often watch younger siblings closely, looking for early signs of the condition -- a lack of shared eye contact, no smiling and no communicative babbling.
But this study suggests those signs won't appear before six months of age.
The study looked at 25 high-risk babies who had autistic siblings, and 25 low-risk peers who had no autistic family members and who had been born after 36 weeks gestation.
Researchers evaluated the children every six months until the age of three, recording the number of times they communicated by smiling, babbling and making eye contact. Examiners were not told which babies were at high- or low-risk.
The researchers found there were few discernable differences between the two groups at six months of age. But by 12 months, the two groups' development had diverged significantly.
Among the babies developing normally, social behavior and communicative behaviour increased significantly around the age of one year. Among the babies later diagnosed with autism, it decreased dramatically around the age of one.
By 12 months, the differences were significant when measuring eye contact; by 18 months, there were vast differences between the two groups in social smiling and other measures.
"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," Sally Ozonoff, a professor of psychiatry and behavioral sciences at the University of California, Davis, and the study's lead author, said in a university news release.
"It also tells us that we should be focusing on social behaviors in our screening, since that is what declines early in life."
The study is published online early and will appear in the March issue of the Journal of the American Academy of Child & Adolescent Psychiatry.
Autism is a developmental disorder of deficits in social skills and communication, as well as in repetitive and restricted behaviors.
While it is usually diagnosed before age three, it's thought that abnormal brain development that probably begins in the womb is likely at the root of the condition.
About one in 100 children develop the condition.
