Language delays found in siblings of children with autism

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Language delays found in siblings of children with autism

October 1st, 2010 in Medicine & Health / Psychology & Psychiatry

Language delays found in siblings of children with autism

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This graph tracks the symptoms of girls in one category of families affected by

autism. Yellow denotes girls with histories of language delay and autistic

traits who were never formally diagnosed as having an autism spectrum disorder

(ASD). Blue represents unaffected girls, red represents those diagnosed with

ASD. Credit: Image courtesy of The American Journal of Psychiatry. Copyright ©

2010 American Psychiatric Association. Used with permission.

Siblings of children with autism have more frequent language delays and other

subtle characteristics of the disorder than previously understood. Girls also

may be mildly affected more often than recognized in the past.

A new study, led by researchers at Washington University School of Medicine in

St. Louis, found mild traits, not strong enough to provoke a diagnosis of

autism, seem to be present in the siblings of affected children at significantly

higher rates than seen in the general population. The findings appear online and

will be published in the November issue of The American Journal of Psychiatry.

" Mild symptoms, called quantitative traits, may be confounding studies that

compare children with autism to their siblings, " says first author N.

Constantino, MD. " Researchers presume one child is affected, and the other is

not, but our findings suggest that although one child may have autism while the

other does not, it's very possible both children are affected to some degree by

genes that contribute to autism. "

Genetic factors exert their influence in different ways. Some families have only

a single child with autism and no other affected children. But in other

families, more than one child may be affected, or other siblings may have a

number of autism characteristics.

Siblings of children with autism have more frequent language delays and other

subtle characteristics of the disorder than previously understood. Girls also

may be mildly affected more often than recognized in the past, according to a

new study, led by researchers at Washington University School of Medicine in St.

Louis. Credit: Washington University BioMed Radio

The study found that approximately one in five siblings thought to be unaffected

experienced language delays or speech problems early in life. The researchers

also noticed many female siblings had subtle traits, but few had full-blown

autism spectrum disorders. Boys are thought to be affected four times more often

than girls. But when the researchers used standardized methods to account for

the presence of quantitative traits, the rate looked more like three affected

boys for every two affected girls.

" The gender difference may not be as pronounced as we once thought it was, "

Constantino says. " If we rely only on a professional diagnosis of autism to

determine who is affected, then boys vastly outnumber girls. But it may be that

many girls are being missed. "

The data comes from almost 3,000 U.S. children in 1,235 families who are part of

the Interactive Autism Network, a national online research registry at

www.IANproject.org. Developed by study co-author Law, MD, director of

medical informatics at Kennedy Krieger Institute in Baltimore, the network has

more than 35,000 participants who share information to help advance autism

research.

For this study, parents provided information about their children using the

Social Responsiveness Scale, a survey developed at Washington University that

identifies traits associated with autism and autism spectrum disorders such as

Asperger Syndrome and Pervasive Developmental Disorder.

About 10 percent of children with autism have genetic mutations believed to

directly lead to the disorder. In others, common gene variations create small

increases in susceptibility. When a child has an accumulation of quantitative

traits, that child will be diagnosed with autism or a related disorder, but

siblings can have subtle quantitative traits without reaching the threshold for

a diagnosis.

" It's not an all-or-nothing condition, " Constantino says. " When we look only at

the full syndrome for inherited traits, we miss a lot of individuals who may

have genetic susceptibility and subtle aspects of autism. In other words, many

siblings of children on the spectrum have significant, subclinical traits of

autism, but, for whatever reason, they never actually develop the disorder. "

Constantino, the Blanche F. Ittleson Professor of Psychiatry and Pediatrics and

director of the Greenleaf Eliot Division of Child and Adolescent

Psychiatry at Washington University, compares it to the difference between

insulin resistance and diabetes. Not all people with insulin resistance are

diabetic, and some never develop diabetes, but they are at a much higher risk

for the disease. The same thing is true for autism, he says.

One striking finding was that among siblings, 20 percent had received a

diagnosis of language delay or speech problems early in life. And half of them

had particular qualities of speech that are autistic in nature. So the

investigators believe that what is aggregating in these families is more than

just the full syndrome of autism. In about 11 percent of families, more than one

sibling has autism, and in many others, these subtle, quantitative signs and

symptoms indicate many undiagnosed children are affected as well.

That's important, Constantino says, because in studies involving DNA tests,

brain imaging or biological comparisons between affected children and their

unaffected siblings, researchers traditionally assume undiagnosed children are

unaffected. But this study would suggest that's not necessarily the case.

The study also found quantitative traits of autism tended to occur more

frequently in children from families with more than one fully affected child. In

families with only one child with autism, it was much more common for that

child's siblings not to have any evidence of quantitative traits. And the study

also found that it was less common for siblings to be affected with those traits

than for non-identical twins — a finding suggested by pooling the results of

this study with a recent twin study from Law and his colleagues at Kennedy

Krieger Institute that used exactly the same methods and the same family

registry.

Law and Constantino say their findings provide insight into the inheritance

patterns of autism and its associated traits. Although those severely affected

with autism spectrum disorders seldom have their own children, those who are

affected with quantitative traits of autism usually grow up to be parents

themselves, and understanding how best to predict patterns of transmission in

families and identifying the specific genetic and environmental factors

underlying those patterns could offer hope for new, more effective interventions

that could be used early in the lives of affected children, Constantino says.

More information: Constantino JN, Zhang Y, Frazier T, Abbacchi AM, Law P.

Sibling recurrence and the genetic epidemiology of autism. The American Journal

of Psychiatry, vol. 167 (11), published online Oct. 1, 2010. http://ajp.psychia

… ryonline.org

Provided by Washington University School of Medicine

" Language delays found in siblings of children with autism. " October 1st, 2010.

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