A major study led by UC Davis MIND Institute confirms that siblings of autistic children have a 20% chance of being diagnosed with autism, emphasizing the importance of early monitoring and intervention.
In a revelatory study, the UC Davis MIND Institute and the Baby Siblings Research Consortium have discovered that siblings of autistic children have a 20% risk of being diagnosed with autism themselves. This incidence is approximately seven times higher than that of infants with no autistic siblings.
Decades of Research Culminate in New Findings
Sally Ozonoff, a distinguished professor in the Department of Psychiatry and Behavioral Sciences at UC Davis, has long been a pioneering researcher in autism recurrence within families. Her team’s latest study, which builds on their 2011 findings, has been published in the journal Pediatrics. The exhaustive research spanned multiple research sites across the United States, Canada and the United Kingdom, incorporating diverse demographic groups.
Rising Autism Rates Spur Renewed Examination
“The rate of autism diagnosis in the general community has been steadily increasing since our previous paper was published,” Ozonoff said in a news release.
In 2011, autism affected 1 in 68 children; today, that figure stands at 1 in 36, according to the Centers for Disease Control and Prevention.
Several factors, including changes in diagnostic criteria and increased recognition of autism in girls, necessitated a thorough re-examination of autism recurrence within families. Despite these changes, the new study’s findings are consistent with those from a decade ago. The familial recurrence rate slightly increased from 18.7% in 2011 to 20.2%, which is statistically insignificant.
“This should reassure providers who are counseling families and monitoring development. It should also help families plan for and support future children,” added Ozonoff.
Key Factors Influencing Recurrence
The rigorous study tracked 1,605 infants with older autistic siblings from as young as six months old across 18 research sites. The findings underscore some critical influences on autism recurrence, notably the sex of both the first autistic child and the new infant.
“If a family’s first autistic child was a girl, they were 50% more likely to have another child with autism than if their first autistic child was a boy,” Ozonoff said.
Furthermore, boys are diagnosed with autism about four times more often than girls.
“The familial recurrence rate if the new baby was a boy was 25%, whereas it was 13% if the new baby was a girl,” she added.
Families with multiple autistic children also show higher recurrence rates. A child with several autistic siblings faces a 37% likelihood of an autism diagnosis, compared to 21% for those with only one autistic sibling.
Socio-Demographic Factors
This study also unveiled how socio-demographic factors, such as race and maternal education levels, can influence recurrence rates. Non-white families saw a 25% recurrence rate, higher than the 18% observed in white families. Maternal education also plays a pivotal role, with recurrence rates varying from 32% among mothers with a high school education or less to 16.9% for those with graduate degrees.
“These findings are new — and critical to replicate,” Ozonoff said. She acknowledged that these findings echo recent CDC reports indicating higher autism prevalence in historically underserved communities.
Looking Ahead
The study highlights the importance of early monitoring and intervention for siblings of autistic children.
“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,” added Ozonoff.
Conducted over nearly a decade, this pivotal study provides invaluable insights, but also calls for further replication and research to deepen our understanding of autism’s familial recurrence.