Parents Often Miss Subtle Autism Signs

March 6, 2010— -- The symptoms of autism tend to emerge in children after six months of age, with a loss of social and communications skills that is more common and more subtle than previously thought, according to a new study that questions previous assumptions about the progression of the condition.

At six months, children with autism spectrum disorder demonstrated behavior similar to other children, gazing at faces, sharing smiles, and vocalizing with similar frequency, researchers reported online in the Journal of the American Academy of Child and Adolescent Psychiatry.

However, autistic children displayed fewer of these behaviors as as they got older, and from six months to 18 months the loss of social communication and skills typically became clear.

While doctors typically caught early signs of autism, the declines were more subtle than previously suggested and most parents -- 83 percent -- did not report regression in the social behaviors and skills.

"These findings lead us to two major conclusions," Sally Ozonoff of University of California Davis Health System in Sacramento and colleagues wrote.

"First, the behavioral symptoms of autism spectrum disorder appear to emerge over time, beginning in the second half of the first year of life and continuing to develop for several years.

"Second, our most widely used and recommended practice for gathering information about symptom onset, parent-provided developmental history, does not provide a valid assessment of the slow decline in social communication that can be observed prospectively."

Autism is thought to emerge in two ways: an early onset pattern and a regressive pattern.

A majority of autistic children are thought to experience the early onset pattern, showing clear signs of the disease in the second year of life but in some cases showing signs before the first birthday.

Those with the regressive pattern are thought to develop normally for the first year of life, then begin losing communications and social skills.