Autism and ADHD May Share More Brain Connections Than We Realize

Autism and ADHD may share some underlying brain patterns, with new research finding that the severity of autism-related traits — not simply an autism or ADHD diagnosis — is linked to differences in brain connectivity.

The findings suggest that some children with ADHD may show brain patterns associated with autism-related symptoms even when they do not meet the criteria for an autism diagnosis.

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The Key Finding: Autism Traits Were Linked to Brain Connectivity

Researchers studied 166 verbal children ages 6–12 who had been diagnosed with either autism or ADHD without autism.

The most important finding was that children with more pronounced autism-related symptoms showed stronger connections between certain brain networks, including the frontoparietal and default-mode networks.

These networks play important roles in areas such as social thinking and executive function.

What makes the finding particularly interesting is that these connectivity patterns were seen regardless of whether the child had an autism diagnosis or an ADHD diagnosis.

In other words, the researchers found that looking at the severity of specific traits may reveal information that diagnostic labels alone do not capture.

Autism and ADHD Are Still Different Diagnoses

This study does not mean that autism and ADHD are the same condition.

Instead, it adds to research suggesting that neurodevelopmental conditions can share certain traits and biological patterns.

Some children with ADHD can have characteristics that resemble autism-related traits without meeting the diagnostic criteria for autism. The researchers wanted to better understand whether there might also be biological similarities underlying those traits.

What Happens as the Brain Develops?

The researchers looked at how connections between brain networks change during development.

Normally, connections between the frontoparietal and default-mode networks tend to decrease as the brain matures, allowing different networks to become more specialized.

The study found that this reduction may happen differently in children with more severe autism-related traits.

That could point to differences in how certain brain networks develop and communicate with one another.

The Study Also Found Genetic Connections

The researchers didn’t stop with brain imaging.

They used a computational approach called spatial transcriptomic analysis to compare the brain connectivity findings with patterns of gene activity across the brain.

The brain regions showing connectivity differences also corresponded with areas where genes involved in brain development are active.

Some of these genes have previously been associated with both autism and ADHD, suggesting that overlapping biological processes may contribute to traits seen across the two conditions.

Why Looking at Symptoms May Matter

One of the most interesting implications of this research is the idea that researchers may learn more by looking at individual traits and their severity rather than focusing only on whether someone has one diagnosis or another.

For example, two children may have different diagnoses but share difficulties involving social thinking, executive function, or other behaviors.

Understanding the biological patterns associated with those specific traits could eventually help researchers develop more precise ways of studying neurodevelopmental differences.

What Does This Mean for Parents?

For parents, this research reinforces something many families already recognize: children with ADHD or autism don’t always fit neatly into separate boxes.

A child may have an ADHD diagnosis while also showing some traits commonly associated with autism. That does not automatically mean the child has autism, but it may be useful to consider the child’s individual strengths and challenges rather than focusing only on the diagnostic label.

The study also highlights why researchers are increasingly interested in understanding neurodevelopmental conditions dimensionally—by examining the range and severity of traits children experience.

What We Still Don’t Know

This was a relatively small brain-imaging study involving 166 verbal children ages 6–12, so the findings don’t establish that autism and ADHD have the same biological cause.

The researchers also aren’t proposing that brain connectivity patterns can currently be used to diagnose autism or ADHD.

Instead, the findings provide another piece of evidence that may help scientists understand why some traits overlap across neurodevelopmental conditions and how brain development may contribute to those differences.

The Bottom Line

The biggest takeaway is that autism-related symptom severity was associated with similar patterns of brain connectivity in children with autism and in some children with ADHD who did not have an autism diagnosis.

The findings suggest that what traits a child experiences—and how strongly they experience them—may reveal important information that diagnostic categories alone cannot capture.

That could eventually lead to a more individualized understanding of autism, ADHD, and the many ways neurodevelopmental differences can appear in children.