Researchers have discovered that children with autism can be set apart from those with other developmental disorders through differences in chemical changes in the brain.
The study, published in JAMA Psychiatry, reveals that gray matter chemical changes that occur between the ages of 3 and 10 years differentiate children with autism spectrum disorder from those with idiopathic (an unknown cause) developmental disorder.
Researchers from the University of Washington, Seattle, analyzed three groups of children in different age groups: one group at age 3 to 4 years, one at 6 to 7 years and one at 9 to 10 years.
All groups had a mix of children with autism spectrum disorder, developmental disorder and "typical development."
The participants with autism spectrum disorder and idiopathic developmental disorder were analyzed using data from proton magnetic resonance imaging (MRI), while those with typical development were assessed using cross-sectional data.
Between 3 and 10 years of age there were specific differences in rates of change in the brain chemicals cerebral gray matter N-acetylaspartate, choline and creatine.
The study authors explain:
"The results from our study suggest that a dynamic brain developmental process underlies autism spectrum disorder, whereas the children with developmental disorder exhibited a different, more static developmental pattern of brain chemical changes."
The study authors also note that the pattern of chemical changes within the autism spectrum disorder group aged 3 to 4 years is comparable to brain chemical changes found in other disorders such as multiple sclerosis, epilepsy and traumatic brain injury, where the N-acetylaspartate level is reduced at the time of onset or injury. This level usually then rises again during periods of remission, after successful treatment or through recovery.
The study authors add: "A model of the return to homeostasis after a disruptive event during earlier development is consistent with theories of early brain inflammatory processes, as yet unproven, as a causal mechanism for cerebral enlargement observed in children with autism spectrum disorder during the preschool years."
"The brain chemical alterations observed in the children with autism spectrum disorder at 3 to 4 years of age likely reflect a process that begins at an earlier stage of development."
More studies at even younger ages may help to determine the timing and underlying observations of the brain developmental process within children with autism spectrum disorder, the researchers add.