Learning Disability Today
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Siblings of autistic children seven times more likely to be diagnosed with autism

Siblings of autistic children are seven times more likely to be autistic as well, which is 20% higher than the rate in infants with no autistic siblings, according to the findings of a recent large study.

The US study, published in Pediatrics, collated data across 18 sites of the Baby Siblings Research Consortium, which is an international network studying the earliest manifestations of autism. A total of 1605 infants with an older autistic sibling from across the US, Canada, and the UK were followed from early in life to three years.

The researchers also found that a child with multiple autistic siblings has a higher chance of autism (37%) than a child with only one sibling who is autistic (21%).

The sex of the infant was also associated with the likelihood of familial recurrence. If the later-born infant was a boy, they were almost twice as likely as a girl to be diagnosed themselves.

Recurrence rate was higher in non-white families

The study confirmed the same research group’s 2011 findings about the likelihood of autism in siblings. They wanted to see how the increasing prevalence of autism diagnoses in the general population—rising from about 1 in 110 children in 2011 to 1 in 36 today –  might influence the recurrence of autism within families, where genetic and environmental factors could play a larger role.

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Sally Ozonoff of the UC Davis MIND Institute who led the study, said: “The rate of autism diagnosis in the general community has been steadily increasing since our previous paper was published. So, it was important to understand if these had any impact on the likelihood of autism recurrence within a family.

“Now we have two large, independent studies that report familial recurrence in the same range. This reinforces how important it is that providers closely monitor the siblings of autistic children for delays in social development or communication. This is especially true in families who have reduced access to care, because early diagnosis and intervention are critical.”

The study also found that the recurrence rate was 25% higher in non-white families. In addition, in families where the mother had a high school education or less, recurrence was 32%. With some college, the rate was 25.5%, and with a college degree the rate was 19.7%. When the mother had a graduate degree, it dropped to 16.9%.

“These findings are new — and critical to replicate,” Ozonoff said. “They do mirror the recent CDC findings that autism is more prevalent in children of historically underrepresented groups.”

She added that if these findings are replicated, they may indicate that there are social determinants of health that may lead to higher rates of autism in families. She emphasised that this study was not designed to answer those critical questions, and more research is needed.

 

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Alison Bloomer
Alison Bloomer is Editor of Learning Disability Today. She has over 25 years of experience writing for medical journals and trade publications. Subjects include healthcare, pharmaceuticals, disability, insurance, stock market and emerging technologies. She is also a mother to a gorgeous 13-year-old boy who has a learning disability.

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