Researchers studying the development of babies in families affected by autism report that motor and visual attention delays at 6 months of age predict a high likelihood of severe autism by age 2. By contrast, children who develop milder forms of autism tend to show their first delays in social and communication skills and do so around 12 months of age.
The findings are important, the investigators say, because they advance understanding of the different ways that autism develops.
The findings also add to a growing body of research that suggests that subtle early signs of autism are evident much earlier than previously thought. At present, autism generally can’t be diagnosed until 18 to 24 months, when its core symptoms of repetitive behaviors and social and communication problems become obvious.
The study’s authors include several members of Autism Speaks Baby Sibling Research Consortium. BSRC investigators focus on the development of babies born into families that already have a child on the autism spectrum. Because autism tends to run in families, these “baby sibs” are at high risk of developing the condition. In fact, earlier BSRC research shows that autism rates among baby sibs are 20 times higher (1 in 5) than in the general population (1 in 68). Another one in five baby sibs develop some autism-related delays and challenges.
The researchers tracked the behavioral and intellectual development of 210 baby sibs using standardized tests and parent interviews at 6, 12 and 24 months of age. For comparison they also tracked the development of 98 babies in families not affected by autism.
Red flags for severe autism
By 24 months, 49 of the 210 baby sibs had a diagnosis of autism. Of these children, those with the most severe autism symptoms had shown delays in motor development and visual attention at 6 months. In particular, they had lagged in the ability to lift their heads and watch people’s faces. At 24 months, their severe symptoms tended to involve challenging behaviors and difficulty with daily living skills such as drinking from a cup.
By contrast, the children who developed milder forms of autism had not shown motor or visual attention delays at 6 months. Their first symptoms appeared around 12 months of age and tended to involve delays in language development.
The researchers caution that the early delays they found at 6 and 12 months are not easily detected without specialized testing. The importance of the findings, they emphasize, may be in advancing understanding of how different forms of autism develop – with an eye to developing early interventions of particular benefit to particular children.
“These studies of high-risk infant siblings show again and again that autism starts early, with some children showing delays and differences in development by 6 months of age,” comments developmental pediatrician Paul Wang, head of medical research at Autism Speaks. “We need to continue this line of research, so we can start interventions at the earliest possible time.”
“This research is also showing that different children may show different paths in the development of their symptoms,” Dr. Wang adds. “This underscores the need to tailor interventions for each child, depending on his or her needs.”
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