Babies who have trouble falling asleep might later be diagnosed with autism, a new study suggests.

In a study led by the University of Washington and published Thursday in the American Journal of Psychiatry, researchers found that "sleep problems in a baby's first 12 months may not only precede an autism diagnosis, but also may be associated with altered growth trajectory in a key part of the brain, the hippocampus."

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"The hippocampus is critical for learning and memory, and changes in the size of the hippocampus have been associated with poor sleep in adults and older children. However, this is the first study we are aware of to find an association in infants as young as 6 months of age," lead author Kate MacDuffie, a postdoctoral researcher at the UW Autism Center, told UW News.

The researchers found that in a sample of more than 400 infants ages 6–12 months, those who were later diagnosed with autism were more likely to have had difficulty falling asleep. This sleep difficulty was associated with altered growth trajectories in the hippocampus.

According to Annette Estes, director of the UW Autism Center and senior author on the study, as many as 80% of children with autism spectrum disorder have sleep problems.

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“In our clinical experience, parents have a lot of concerns about their children’s sleep, and in our work on early autism intervention, we observed that sleep problems were holding children and families back,” Estes, who is also a UW professor of speech and hearing sciences, told UW News.

To consider links among sleep, brain development and autism, researchers at the Infant Brain Imaging Study Network examined MRI scans of 432 infants, surveyed parents about sleep patterns, and measured cognitive functioning using a standardized assessment.

Researchers at the University of Washington, University of North Carolina at Chapel Hill, Washington University in St. Louis and the Children’s Hospital of Philadelphia then evaluated the kids at 6, 12 and 24 months old. They surveyed parents about their child’s sleep, including how long it took for the child to fall asleep or to fall back asleep if awakened.

“Our findings are just the beginning — they place a spotlight on a certain period of development and a particular brain structure but leave many open questions to be explored in future research,” lead author MacDuffie said.

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