Children with autism spectrum disorders usually aren't diagnosed until they are at least 2 years old, but a new study finds that signs of the condition are apparent as early as two months after birth.
Researchers focused on babies' ability to make eye contact with caregivers, since lack of eye contact is one of the hallmarks of autism. Among typical children, interest in the eyes increased steadily with age. But for children with autism, interest in the eyes waned starting between 2 and 6 months of age.
By the time they reached their second birthdays, levels of eye fixation among children with autism were only half as high as levels seen in typically developing children, according to a report published Wednesday by the journal Nature.
Though researchers expected to see a difference between the two groups of kids, they were surprised that the infants who were later diagnosed with autism started out developing just like their peers. That suggests that "some social adaptive behaviors may initially be intact" in babies' brains, which would "offer a remarkable opportunity for treatment," the researchers wrote.
Warren Jones and Ami Klin of the Marcus Autism Center at Emory University School of Medicine in Atlanta recruited 110 infants for their study. Among them, 59 had a full sibling with an autism spectrum disorder and thus were considered at high risk of developing the condition themselves. An additional 51 infants who had no first-, second- or third-degree relatives with autism were considered low-risk, and they served as controls.
The infants were shown "scenes of naturalistic caregiver interaction" while the researchers used eye-tracking technology to monitor where the babies focused their gazes. They measured the proportion of time spent paying attention to the woman's eyes, mouth, body (including neck, shoulders and hair) and nearby inanimate objects. The subjects were tested 10 times over the course of the study, when they were 2, 3, 4, 5, 6, 9, 12, 15, 18 and 20 months old.
By the time the toddlers were 3 years old, 13 were formally diagnosed with an autism spectrum disorder – 10 boys and two girls from the high-risk group and one boy from the control group. For the sake of simplicity, they focused their analysis on boys: 11 with autism and 25 without.
The data showed that distinct differences in eye interest became apparent when the babies were between 2 and 6 months old. During those early months, the boys in the control group spent more time focused on the caregiver's eyes than the mouth, body or object regions. But for the boys with autism, interest in the caregiver's eyes steadily declined after the 2-month test.
The researchers also found that steeper declines in eye interest tended to be linked to more severe cases of social disability.
Other differences emerged as well. Though boys in both groups showed increasing interest in the caregiver's mouth up through the age of 18 months, the typically developing boys lost interest in the body and object regions much more quickly than the boys with autism.
"These results, although still limited in sample size, document the derailment of skills that would otherwise guide typical socialization," Jones and Klin wrote.
If the results are confirmed and doctors are able to identify children with autism as early as 2 months of age, therapists could intervene earlier – and perhaps get better results.
"The sooner we are able to identify early markers for autism, the more effective our treatment interventions can be," Dr. Thomas Insel, director of the National Institute of Mental Health, said in a statement.
The study was funded by NIMH.