Autism may be detectable in infants as young as 6 months old, according to a study released Friday in the American Journal of Psychiatry, suggesting the condition has a stronger genetic and biological root.
The study, which tracked MRI images of 92 infants from 6 to 24 months, found that infants who went on to develop autism may have had brain abnormalities visible on MRI at 6 months of age, before the development of clinical symptoms.
The infants studied were already considered at high risk for the condition because their siblings were diagnosed with autism.
Researchers tracked brain changes in infants at 6 months-, 1 year-, and 2 years old. Then, they formally tested for autism using the standard diagnostic test at 2 years old, the typical age when autism is diagnosed.
Twenty-eight infants whose MRI results showed slower brain connections went on to be diagnosed with an autism spectrum disorder.
Previous studies have looked at brain changes in babies as young as 1 year old, but researchers said the new study is the first to track changes in infants as young as 6 months old.
According to Dr. Nancy Minshew, director of the NICHD Collaborative Program of Excellence in Autism at the University of Pittsburgh, who was not involved in the study, the current findings suggest that a child might have autism long before he or she begins to show outward signs.
"Parents and primary care physician determination of onset of autism or ASD in the second or third year of life is not an accurate assessment of onset," said Minshew. "This adds to the evidence that autism develops on its own, so to speak, and not because parents did something or did not do something to cause autism."
Tracking changes could lead to earlier autism screening and intervention, which may lead to improved developmental outcomes, the authors wrote.
But, according to ABC News' chief health and medical editor Dr. Richard Besser, the imaging results are not distinguishable enough to make a clear-cut diagnosis.
"For a diagnostic test to be of value, you want to see extensive separation between your affected and not-affected groups," said Besser. "There appears to be a ton of person-to-person variability. The likelihood that this will ever lead to a diagnostic test is pretty slim."
The study authors acknowledged that the study was only performed on infants' with a family history of autism, which inherently indicated they, too, were at high risk for the condition. The test might be limited to babies already known to be at high risk.