Autism may have subtypes that are genetically distinct from each other

Recent research suggests that the timing of autism diagnoses in children may be significantly influenced by genetic factors, shedding light on the complexities of autism development.

“This research bolsters the perspective that autism could represent a spectrum of conditions,” states Natalie Sauerwald from the Flatiron Institute in New York, who did not participate in the study.

Autism is classified as a neurodevelopmental disorder marked by challenges in social interaction paired with restricted behaviors and interests. According to estimates from the World Health Organization, approximately one in 127 individuals are diagnosed as autistic.

“Our primary inquiry centered on understanding why some individuals are diagnosed with autism later in life,” explains Varun Warrier from the University of Cambridge.

The research team collected data from individuals diagnosed with autism between the ages of 5 and 17. Caregivers provided information regarding the children’s emotional, social, and behavioral growth to analyze connections between these factors and the age of diagnosis.

It has been established that factors like a child’s sex and socioeconomic background may affect the timing of their diagnosis, with earlier diagnoses being more frequent in boys and children from affluent families. However, the analysis revealed that these influences are relatively minimal, with no single factor explaining more than 10 percent of the variance, according to Warrier.

The findings indicated that autistic children tend to develop following different paths. “We identified two major categories of autistic individuals,” notes Warrier. One group displayed early difficulties that persisted over time, while the other encountered fewer challenges in early childhood but faced increasing difficulties entering adolescence. This insight accounts for 10 to 25 percent of the variance in diagnosis age.

Moreover, the collected data pointed to genetic differences between the two groups. Those diagnosed later possessed a distinct assortment of common genetic variants compared to their early-diagnosed counterparts, which could explain 11 percent of the variance in diagnosis age. The researchers acknowledged limitations in their data concerning rare and spontaneous genetic variants.

Despite these classifications, Sauerwald cautions that the distinction is not absolute. “There’s an overlap between the two groups, likely because they aren’t strictly separate,” she remarks. Warrier similarly emphasizes that these groups exist “on a gradient.”

It is critical to note that neither of the groups should be viewed as having milder or more severe forms of autism. Recent studies have indicated that autism may manifest in various forms, as noted in a July publication by Sauerwald and her team, where they identified four moderately distinct subgroups characterized by differing symptoms, behaviors, and genetic backgrounds.

Warrier’s findings also indicated that children diagnosed later in life are more likely to have genetic variants linked to other conditions, including ADHD and post-traumatic stress disorder. This link aligns with findings from Sauerwald’s research, which noted a similar connection between late autism diagnosis and ADHD, another form of neurodiversity. The underlying reasons for this connection are still unclear, with Sauerwald highlighting a notable deficiency in data related to ADHD and the specific symptoms experienced by affected individuals.

Gaining a deeper understanding of the potential subtypes of autism could ultimately enhance diagnostic procedures, allowing for more customized support for autistic children and their families. “This progress can only lead to improved quality of life for individuals—by enhancing our understanding of their conditions, determining how to provide assistance, and identifying what exact needs they have or do not require,” states Warrier.