The way that babies as young as six months look at the eyes of other people may be an early sign of autism, a new study suggests.
Researchers looked at brain scans of infants as they were shown pictures of faces, and those who were later diagnosed with autism showed marked differences in brain activity from those who were not later diagnosed with the condition when the eyes in the pictures were directed at the infants.
The study included 104 babies who either had a higher risk of developing autism, because they had a sibling with the condition, or had no family history of autism.
"This study takes us a step further in understanding what goes on in the brain that subsequently causes autism to emerge in children," said study researcher Mayada Elsabbagh, a scientist at McGill University in Canada.
The study is published today (Jan. 26) in Current Biology.
Infant brain responses could be an early sign
About 1 in 110 children in the U.S. has autism, according to the Centers for Disease Control and Prevention. Parents who have one child with autism are 2 to 8 percent more likely to have a second child with the disorder.
Diagnoses of autism are based on children's social behavior, and are generally made in children 2 years and older.
But parents often know something is wrong before that age.
"As early as infancy, they notice that something is different, but it's difficult to have it confirmed with a diagnosis until the child ages," Elsabbagh said.
Study findings suggest there might be a way to diagnose the disorder earlier based on infant brain responses, and that treatments for the condition may be more effective when given at earlier ages.
"The next step is to increase our knowledge on how to diagnose earlier, and provide access to earlier intervention, which we know can reduce the impact of the symptoms," Elsabbagh said.
Making eye contact could be the key
In the new study, researchers recruited families from the British Autism Study of Infant Siblings, which tracked infants starting at 5 months of age until they were 3 years old.
They tested 54 infants who had a sibling with autism, and so were at high risk of developing the condition, and 50 infants who did not, and so were the control group.
The infants, at 6 to 10 months, were shown faces that switched from looking at them to looking away from them, a way of gauging their response to eye contact with another person.
Researchers used sensors placed on the infants' scalps to measure their brain in response to eye gaze directed toward or away from the baby.
They found that of the 54 infants at higher risk, the 17 who were diagnosed with autism by 3 years of age tended to have different brain responses from the 50 infants who were not at risk, and were not later diagnosed with the condition.
But Elsabbagh cautioned that the study's findings were imperfect.
"Not every child that developed autism has brain function that showed a huge difference," she said. "It could be some other factor that prevents autism from emerging."
Researchers also only looked at children who were at high risk of autism.
"These children are at higher risk than children in the general population — children who don't have an older sibling affected by autism," said Alycia Halladay, director of research for Autism Speaks, a group that advocates for autism research, who was not involved with the study.
"So we don't know if these findings are applicable to other children with autism, or to just those who are at risk," she said.
But Halladay did point out that the study raised interesting questions about the role of early social behaviors like looking or tracking a child's eye gaze.
"Further research needs to be done on whether brain activity can be the basis for early intervention," she said.
Pass it on: How an infant responds to eye contact could determine whether they are at risk for autism.