The age at which a child is diagnosed is related to their genetics, according to a recent international study published in Nature.

Additionally, autism diagnosed in early childhood differs genetically and developmentally from autism diagnosed later in life.

The research analyzed behavioral data from children and teens in the UK and Australia, along with genetic data from more than 45,000 autistic people across Europe and the United States.

“We found that, on average, individuals diagnosed with autism earlier and later in life follow different developmental pathways, and surprisingly have different underlying genetic profiles,” lead researcher Xinhe Zhang said in a statement.

The study focused on a type of genetic contributor to autism diagnosis, specifically, polygenic factors, which are common inherited gene variants that only account for about 11 percent of the variation in age at autism diagnosis.

Different Developmental Pathways

Scientists from the University of Cambridge Department of Psychiatry found that children diagnosed with autism before age 6 often show difficulties with giving enough attention to social interactions or proactively socializing with other people earlier in life. Conversely, those diagnosed during adolescence tend to face social and behavioral challenges later, along with higher risks of conditions like depression.

The genetic makeup of those diagnosed later resembles that of attention-deficit/hyperactivity disorder (ADHD), depression, and post-traumatic stress disorder (PTSD) more than that of children diagnosed early.

“The term ‘autism’ likely describes multiple conditions. For the first time, we have found that earlier and later diagnosed autism have different underlying biological and developmental profiles,” senior study author Varun Warrier said in the statement.

The differences in the behavior of children diagnosed earlier and later suggest the timing of diagnosis reflects more than just health care access or awareness, Zhang said.

What the Findings Mean for Autism Screening

The findings could affect how autism is understood, studied, and supported, according to researchers.

“Some of the genetic influences predispose people to show autism traits from a very young age that may be more easily identified, leading to an earlier diagnosis,” Warrier stated. 

For example, having comorbid mental health issues, including schizophrenia and PTSD, experiencing childhood maltreatment, and self-harm are more strongly genetically linked to late autism diagnosis.

“Often people who seek an autism diagnosis believe that they have only the loss of social emotional reciprocity and rigidity/sameness that autism features as its main components,” Dr. Ashvin Sood, a board-certified child and adolescent psychiatrist who works with autistic adults and children but was not involved in the study, told The Epoch Times.

“What they fail to recognize is that autism can be associated with a whole slew of other conditions.”

Some children may have features that parents or caregivers do not pick up on until they cause “significant distress” later on, he added. Understanding how the features of autism emerge not just in early childhood but in later childhood and adolescence “could help us recognize, diagnose, and support autistic people of all ages.”

If later-diagnosed profiles overlap more with ADHD, depression, and trauma-related vulnerabilities, then comprehensive evaluations must look for co-occurring conditions rather than treating them as afterthoughts, Debra Kissen, a licensed clinical psychologist and the CEO and founder of Light On Anxiety CBT Treatment Centers, told The Epoch Times.

“For those youth, the most effective plan may combine autism-affirming supports with evidence-based care for attention, mood, and stress recovery,” Kissen added. Autism-affirming support involves recognizing and welcoming neurodivergent minds as equally valid, whole, and not in need of fixing.

The study findings add “precision” to intervention strategies, according to Kissen. “If early-diagnosed and later-diagnosed profiles differ biologically and developmentally, our screening shouldn’t be ‘one-size-fits-all.’”

In practice, Kissen said, this means broadening pediatric screening beyond language and eye contact to include sensory profiles, motor planning, and early social learning cues. Additionally, providing different children with various tools and therapies to help them function better, including allowing them to use pictures and words on a screen to communicate if they do not speak, as well as occupational therapy to help with sensory problems.