New study confirms high autism recurrence rates in families with autistic children

BALTIMORE, August 7, 2024— A study conducted by top researchers, including those from Kennedy Krieger Institute, reveals that one in five children (20%) with an older sibling diagnosed with autism spectrum disorder (ASD) are likely to be diagnosed with the disorder as well. Data show that when a child has more than one older sibling with autism, the family recurrence rate then rises to over 36%.

This research analyzed data from 1,605 infants with an older sibling with ASD. The infants were evaluated multiple times from ages 6 months through 36 months. The study, conducted by organizations involved with the Baby Siblings Research Consortium, including Kennedy Krieger Institute, concluded that the rate of autism recurrence is seven times higher in families with an autistic child compared to the general population. This finding is in line with earlier research, but investigators said this new study used more comprehensive reporting strategies.

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 and was involved in this research. She says the findings show the importance of extra developmental monitoring for babies born into families with autistic children.

“Pediatricians and family members have to keep a diligent eye on infants born into families with an already diagnosed autistic child,” Dr. Landa said. “Early referral for diagnostic evaluation is crucial to ensure support, resources, and intervention.”

The study found that the sex of a child significantly influences the chance of recurrence. Younger siblings of female autistic children were more likely to develop autism (34.7%) compared to siblings of males (22.5%). Male younger siblings also had a higher likelihood of being autistic than females.

Additionally, the study found the reoccurrence of ASD in white families was 17.8%, while it increased to 25% across other races collectively.

“The scale and diversity of this group of infants, compared to our prior recurrence rate study published over a decade ago, gives strong evidence that these recurrence rates are reliable," Dr. Landa said. "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.”

Maternal education also showed a significant effect on ASD recurrence rates. The study reported a higher recurrence rate of 32.6% for mothers with a high school education or less. That percentage decreases for mothers who obtained a college degree and/or a graduate degree. It was also noted that this effect was significant only 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. The study strengthened its findings by using diagnoses only from ASD experts, eliminating biases associated with parent interviews. Additionally, new diagnostic criteria have enhanced the strength of these findings. 

Dr. Landa notes that the study’s findings reveal how factors such as race, sex, education, and healthcare access influence the timeliness of diagnoses and support. She emphasizes the need for improved efforts to address disparities as we continue to learn more about ASD.

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

About Kennedy Krieger Institute 
Kennedy Krieger Institute, an internationally known, non-profit organization located in the greater Baltimore/Washington, D.C. region, transforms the lives of more than 27,000 individuals a year through inpatient and outpatient medical, behavioral health and wellness therapies, home and community services, school-based programs, training and education for professionals and advocacy. Kennedy Krieger provides a wide range of services for children, adolescents and adults with diseases, disorders or injuries that impact the nervous system, ranging from mild to severe. The Institute is home to a team of investigators who contribute to the understanding of how disorders develop, while at the same time pioneer new interventions and methods of early diagnosis, prevention and treatment. Visit www.kennedykrieger.org/ for more information about Kennedy Krieger.

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