1 in 5 Kids With an Autistic Sibling Show Subtle Symptoms Too

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It’s not easy being the brother or sister of an autistic child. “Typical” siblings sometimes feel embarrassed by or responsible for their autistic sib, or may feel jealous of all the attention he gets. Now researchers have found that the siblings of autistic children are affected in another way: up to 20% of these brothers and sisters may have subtler autism-related symptoms of their own. (More on Time.com: Autistic Kids: The Sibling Problem).

The new study involved nearly 3,000 children in 1,235 families with at least one autistic child. All the families had participated in a larger online registry of 35,000 autism-affected families called the Interactive Autism Network.

Of the families included in the current study, 10.9% had more than one child diagnosed with an autism spectrum disorder (ASD). This is consistent with previous research showing that siblings of autistic children are at much higher risk of having an ASD than other children — 22 times higher than children without affected siblings.

But what surprised the researchers was that an additional 20% of the siblings of autistic children showed language delays, and half of these kids had subtle speech problems that are characteristic of autism, such as reversing pronouns or using invented words. The rate of these subtle problems was higher in girls than in boys, and the study’s author suggests that when such mild traits are taken into consideration, the ratio of autism-affected boys to girls would be about 3 to 2 — which contrasts with the currently accepted ratio of four boys with autism for every girl. (More on Time.com: 6 Tips for Traveling With an Autistic Kid).

The findings add to the evidence for some kind of genetic basis of autism. CNN reports:

This suggests that many children who do not have an autism diagnosis are still affected by the condition, even if only in a mild way, study authors said. In the general population, about 7 percent of children receive a diagnosis of a speech or language disorder, said lead author Dr. John Constantino of Washington University in St. Louis, Missouri.

Many of these children will outgrow or get training to overcome their language problems and have little trace of those abnormalities later in life, Constantino said. But they may provide clues into the mechanism of inheritance of autism in some families.

Constantino’s research also suggests that parents should be aware of speech or social problems in the unaffected siblings of autistic children. Constantino and Dr. Scott Hunter, director of pediatric neuropsychology at the University of Chicago Medical Center, spoke with HealthDay:

Both experts thought that it would be a good idea for families with one autistic child to have their other children screened, and Hunter said that you should definitely seek a thorough evaluation if you notice any trouble in language acquisition in children who don’t have autism.

“If you are a parent of a child with autism, it’s probably important to talk to your pediatrician about your other child’s development,” said Hunter.

“The likelihood of other children in the family potentially being affected by a language or social impairment is relatively high, so keep an appropriate level of vigilance. These less-severe symptoms may nevertheless be substantially impairing in school and friendships,” explained Constantino.

The findings were published in the November issue of the American Journal of Psychiatry. For more information on autism spectrum disorders, click here and here.

More on Time.com:

PHOTOS — Inside a School for Autistic Children

The Mysterious Case of Donald T, Autism’s First Diagnosis

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