a young child holding a toyAt what age is autism apparent in children? In the United States, the average age of diagnosis for autism is four years old, but research from the University of Illinois at Urbana-Champaign found that while a few autism-related behaviors surface in children as young as nine months, many such behaviors are observable by age two.

The researchers used data from the Early Childhood Longitudinal Study (ECLS), selecting a birth cohort of a nationally representative sample of children born in 2001; ECLS followed children from birth through kindergarten. Unlike many other studies, ECLS did not rely on parents’ observations. Trained interviewers conducted developmental surveys at children’s homes when the children were aged nine months and two years. Parents only reported whether or not their child was diagnosed with autism when the child was four years old.

For the present study, the researchers examined approximately 10,000 children: 100 with autism, 1,100 with disabilities like hearing impairments or intellectual disability, and 7,700 typically developing children.

Nine-month-old children who were later diagnosed with autism had similar developmental patterns to children who did not have autism. However, nine-month-old children later diagnosed with autism were more likely to wake up three or more times per night compared to typically developing children and children with disabilities. Both children with autism and other disabilities were more likely to quickly transition from whimpering to intense crying, suggesting that these groups find it difficult to manage emotions.

By age two, children who were later diagnosed with autism manifested a number of behavioral and cognitive differences. They were using less words than their peers—10 compared to 22 for children with disabilities and 30 for typically developing children—and performing worse in naming objects and using words. The children with autism also demonstrated worse motor skills when it came to sitting, standing, and walking or grasping and manipulating objects.

The two year-olds with autism behaved differently when interacting with their mothers than the children in other groups. They smiled less and cried more and they demanded more maternal attention.

The findings suggest that autism can be identified in children as young as two. This could help young children with autism access early treatments.

This research is published in the Journal of Early Intervention.

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