Washington: Nascent symptoms of autism such as a lack of shared eye contact, smiling and communicative babbling appear in babies after the first six months of their birth.
Autism is a pervasive developmental disorder of deficits in social skills and communication, as well as in repetitive and restricted behaviours, with onset occurring prior to age three.
Researchers conducted the study over five years by painstakingly counting each instance of smiling, babbling and eye contact during examinations until the children were three years old.
They found that by 12 months the two groups` development had diverged significantly. Intentional social and communicative behaviour among children developing normally increased while among infants later diagnosed with autism it decreased dramatically.
"This study provides an answer to when the first behavioural signs of autism become evident," said Sally Ozonoff, professor of psychiatry and behavioural sciences at the University of California-Davis (UC-D), who led the study.
"Contrary to what we used to think, the behavioural 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 six and 12 months of age," Ozonoff added.
Abnormal brain development, probably beginning prenatally, is known to be fundamental to the behaviours that characterise autism. Current estimates place the condition`s incidence at between 1 in 100 and 1 in 110 children in the US, said a university release.
The study is published online and will appear in the March issue of the Journal of the American Academy of Child and Adolescent Psychiatry.
PTI
