Siblings of autistic children may share some symptoms

[Guest guest]

http://www.sciencenews.org/view/generic/id/64096/title/Siblings_of_autistic_chil\

dren_may_share_some_symptoms

Siblings of autistic children may share some symptoms

Survey finds surprising number of girls affected but not diagnosed

By Bruce Bower Web edition : Thursday, October 7th, 2010

Autism seems to play a genetically inspired hide-and-seek game in some families.

Undiagnosed siblings in families that include two or more children with autism

often grapple with language delays, social difficulties and other mild symptoms

of the disorder, a new study suggests.

Genes prompt autism symptoms of varying intensity among members of these

families, including in some kids who don't qualify as having an autism spectrum

disorder, say psychiatrist Constantino of Washington University School of

Medicine in St. Louis and his colleagues. Researchers have generally limited

their search for DNA peculiarities to children diagnosed with autism or related

disorders (SN: 7/3/10, p.12), a strategy that overlooks those with mild autism

signs, Constantino's group asserts in a paper published online October 1 in the

American Journal of Psychiatry.

" Subtle aspects of the autistic syndrome have not been accounted for in most

studies of its intergenerational transmission, " Constantino says.

By including individuals with mild autism symptoms in DNA studies, researchers

could enlarge their sample sizes and amplify the statistical power of studies to

find genetic effects, remarks psychiatrist ph Piven of the University of

North Carolina at Chapel Hill.

" Given Constantino's data, it is clearly wrong to label all nonautistic

individuals as unaffected by an underlying genetic liability for the condition, "

Piven says.

Approximately one in five siblings of children with autism who don't meet

criteria for the disorder display mild or " subclinical " autism traits,

Constantino's team estimates. These traits consist of language delays, the use

of odd or repeated phrases and other unusual speech qualities and difficulties

interacting with others. Most such children come from families with at least two

other youngsters who have an autism spectrum disorder.

Four times as many boys as girls meet psychiatric criteria for autism. But the

inclusion of mild autism traits narrows that ratio to three boys for every two

girls.

Males and females inherit the same autism-related genes, but in females those

genes frequently interact with other genetic factors or with environmental

influences to reduce the severity of symptoms, Constantino theorizes.

Subclinical autistic traits deserve close scrutiny for possible detrimental

effects on children, Constantino adds. Kids with undiagnosed autism-related

social deficits may find it hard to make friends and could experience a

worsening of other conditions such as learning disabilities and

attention-deficit hyperactivity disorder.

Subclinical traits may have benefits as well, he adds. Disinterest in social

activities and a focus on details might boost math, science and computer skills.

Constantino's team assessed signs of autism in 2,920 children from 1,235

families participating in a national online research registry. Each family in

the registry includes at least one child with an autism spectrum disorder and at

least one biological sibling. Data came from questionnaires completed by

parents.

Their responses indicated that 134 families, or 11 percent, had more than one

child diagnosed with autism. About one in four families, including nearly all of

those with multiple autism cases, also contained siblings with mild symptoms.

Among mildly affected boys and girls, 20 percent had received a diagnosis of

language delay or speech problems early in life, double the prevalence in the

general population.

Constantino emphasizes that, for three in four families, one child had an autism

spectrum disorder and the rest showed no signs of autism. He suspects that

autism-related genes work in an all-or-nothing fashion in these families.

Clinicians should measure the intensity of autism symptoms over time in

individual children and determine points at which interventions become

necessary, much as they use growth charts to ascertain childhood obesity, he

recommends.