A study conducted by top researchers, including those from the Kennedy Krieger Institute, has revealed that one in five children (20%) with an older sibling diagnosed with autism are also likely to be diagnosed with the disorder. The data shows that when a child has more than one older sibling with autism, the family recurrence rate rises to over 36%.

This study analyzed data from 1,605 infants who had an older sibling with autism. The infants were evaluated multiple times from 6 months to 36 months. The research, conducted by organizations such as the Baby Siblings Research Consortium and the Kennedy Krieger Institute, found that the risk of autism recurrence is seven times higher in families with an autistic child compared to the general population. This result is consistent with previous research, but the investigators noted that this new study employed more comprehensive reporting methods.

Dr. Rebecca Landa, PhD, CCC-SLP, serves as the Vice President and Executive Director for the Center for Autism Services, Science, and Innovation (CASSI) at Kennedy Krieger. She was involved in this research and says the findings demonstrate the importance of additional developmental monitoring for babies born into families with autistic children.

“Pediatricians and family members need to diligently monitor infants born into families with a diagnosed autistic child,” Dr. Landa emphasized. “Early referral for diagnostic evaluation is crucial to ensure support, resources, and intervention.”

The research discovered that the gender of a child has a significant impact on the likelihood of autism recurrence. It was found that younger siblings of female autistic children had a greater tendency to develop autism (34.7%) compared to siblings of males (22.5%). Moreover, male younger siblings were also more likely to be autistic than their female counterparts.

Additionally, the study found that the recurrence of autism in white families was 17.8%, while it increased to 25% across other races combined.

“The scale and diversity of this group of infants, compared to our previous recurrence rate study published over a decade ago, provides strong evidence that these recurrence rates are reliable,” said Dr. Landa. “We need to update recurrence studies like these due to the population increase in autism prevalence over the years. We know so much more now in 2024 than we did in 2011.”

The study found that maternal education has a significant effect on autism recurrence rates. Mothers with a high school education or less had a higher recurrence rate of 32.6%, which decreased for mothers with a college or graduate degree. This effect was only significant for mothers and not for fathers.

Researchers say the prevalence of autism has risen to 1 in 36 children over the last decade. They attribute this increase to improved awareness of autistic females and cognitively able/verbal children rather than a true rise in autism rates.

Dr. Landa points out that the study’s findings show how race, sex, education, and access to healthcare can affect the timing of diagnoses and support. She stresses the importance of making better efforts to address disparities as we gain more knowledge about autism.

“It’s essential to ensure that families facing social inequities have access to resources, education, and providers,” said Dr. Landa. “Every child with autism and their family deserves this support.”