Autism among siblings more common than once thought

Nearly 19% of infants who have an older brother or sister with an ASD also developed autism by age 3, a study shows.

By Christine S. Moyer — Posted Aug. 22, 2011

Print  |   Email  |   Respond  |   Reprints  |   Like Facebook  |   Share Twitter  |   Tweet Linkedin

Pediatricians should closely monitor infants who have older siblings with an autism spectrum disorder, because those infants have an increased risk of having autism, a study shows.

The study, published online Aug. 15 in Pediatrics, found that 19% of such infants had an ASD when they were 3. Autism spectrum disorder includes autistic disorder, Asperger's syndrome and pervasive developmental disorder not otherwise specified.

The autism risk is even greater among children who have several older siblings with one of the neurodevelopmental disorders.

The 19% increase is up from previous estimates that autism occurred in 3% to 10% of children who have a sibling with the condition.

Lead study author Sally Ozonoff, PhD, said pediatricians should ask parents of high-risk infants questions about the baby's development during well-child visits. Such questions could include whether the child is interested in people and whether the infant is babbling.

If a red flag is identified, doctors are encouraged to refer the patient to a specialist for further testing and treatment. Warning signs include children who do not respond to their name by age 1 and those who avoid eye contact, have delayed speech and language skills, and repeat words or phrases, according to the Centers for Disease Control and Prevention.

Early specialized intervention could help reduce symptoms of the condition and overall disability, the study said.

Ozonoff encouraged pediatricians to think of the 19% increase as an average risk for children with older autistic siblings. She said the risk is higher for some children and lower for others.

"We can't say what a family's actual specific risk is," said Ozonoff, a professor of psychiatry and behavioral sciences at the UC Davis MIND Institute in California.

Alarming results

An average of 1 in 110 children in the United States has an ASD, the CDC said. Often, there are developmental concerns about the child before age 3.

Researchers examined data on 664 infants who were part of the Baby Siblings Research Consortium, an international network that pools data from individually funded research sites to study the earliest behavioral and biomedical markers of ASDs.

Participants in the Pediatrics study were from the U.S. and Canada. Each had at least one older sibling diagnosed with an ASD.

The infants were followed from early life to 36 months, when they were screened using the Autism Diagnostic Observation Schedule and the Mullen Scales of Early Learning. The diagnostic observation schedule assesses autism symptoms, and the scales of early learning measure nonverbal cognitive skills, language abilities and motor skills.

Researchers found that ASDs were more common among male infants, with 26% diagnosed with one of the conditions compared with 9% of females. Among participants who had multiple siblings with an ASD, 32% developed one of the conditions.

"Although the results were really alarming, it's important to keep in mind that overall, about 80% of the infants [in the study] did not develop autism," Ozonoff said.

Back to top

External links

"Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study," Pediatrics, published online Aug. 15 (link)

Back to top



Read story

Confronting bias against obese patients

Medical educators are starting to raise awareness about how weight-related stigma can impair patient-physician communication and the treatment of obesity. Read story

Read story


American Medical News is ceasing publication after 55 years of serving physicians by keeping them informed of their rapidly changing profession. Read story

Read story

Policing medical practice employees after work

Doctors can try to regulate staff actions outside the office, but they must watch what they try to stamp out and how they do it. Read story

Read story

Diabetes prevention: Set on a course for lifestyle change

The YMCA's evidence-based program is helping prediabetic patients eat right, get active and lose weight. Read story

Read story

Medicaid's muddled preventive care picture

The health system reform law promises no-cost coverage of a lengthy list of screenings and other prevention services, but some beneficiaries still might miss out. Read story

Read story

How to get tax breaks for your medical practice

Federal, state and local governments offer doctors incentives because practices are recognized as economic engines. But physicians must know how and where to find them. Read story

Read story

Advance pay ACOs: A down payment on Medicare's future

Accountable care organizations that pay doctors up-front bring practice improvements, but it's unclear yet if program actuaries will see a return on investment. Read story

Read story

Physician liability: Your team, your legal risk

When health care team members drop the ball, it's often doctors who end up in court. How can physicians improve such care and avoid risks? Read story

  • Stay informed
  • Twitter
  • Facebook
  • RSS
  • LinkedIn