How Autism and ADHD Overlap in the Brain
Up to 70% of people with autism also have ADHD. New brain-imaging and genetic research reveals why these two conditions so often travel together—and why clinicians are rethinking how they diagnose and treat both.
Two Conditions, One Brain
For decades, psychiatrists treated autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD) as entirely separate conditions. The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) even prohibited diagnosing both in the same person. That changed in 2013, when the DSM-5 formally acknowledged that the two conditions can co-occur—a shift that opened the door to research now revealing just how deeply intertwined they are.
Meta-analyses estimate that 50 to 70 percent of individuals with autism also meet criteria for ADHD. A 2025 study found that roughly 45 percent of adults with ADHD display notable autistic traits, yet only about 1.7 percent carry a formal dual diagnosis—suggesting widespread under-recognition.
Shared Genes, Shared Wiring
Twin and family studies have long hinted at a common genetic foundation. A 2022 genomic study identified at least seven chromosomal regions linked to both conditions, with genes in the dopaminergic, serotonergic, and glutamatergic neurotransmitter systems implicated in each. Estimates suggest that autism and ADHD share 50 to 70 percent of their genetic influences.
Brain-imaging research adds anatomical detail. A study published in Molecular Psychiatry by Dr. Adriana Di Martino's team at the Child Mind Institute analyzed resting-state fMRI scans from 166 children aged six to twelve. The researchers found that autism symptom severity—not diagnostic label—predicted increased connectivity between the brain's frontoparietal and default-mode networks. This pattern appeared in children diagnosed with autism and in those diagnosed with ADHD, pointing toward shared neurobiology that cuts across traditional categories.
"By focusing on shared brain–gene expression patterns linked to autism symptoms across both ASD and ADHD, we can point towards a shared biological basis." — Dr. Adriana Di Martino, Child Mind Institute
Where They Diverge
Despite the overlap, the two conditions are not identical. Both involve attention differences, but they manifest differently. People with autism tend to hyperfocus on specific interests and prefer routine, while those with ADHD struggle with attention regulation and often seek novelty. Executive function studies show that children with autism face greater difficulties with planning and cognitive flexibility, whereas children with ADHD show more pronounced challenges with impulse inhibition.
Selective attention problems appear in about 98 percent of children with ASD, compared with roughly 21 percent of children with the inattentive subtype of ADHD—suggesting that attention difficulties in autism may be inherent to the condition rather than a sign of simple co-occurrence.
The AuDHD Experience
The informal term "AuDHD" has gained traction in patient communities to describe what living with both conditions feels like. Many report a kind of internal tug-of-war: autism's craving for predictability collides with ADHD's restless need for stimulation. One person described it as a "constant war with yourself."
Diagnosis remains difficult. Symptoms can mask each other—ADHD's social impulsivity may camouflage autistic social difficulties, while autism's structured routines can hide ADHD-related disorganization. Women and girls are especially likely to go unrecognized because of social masking behaviors that obscure both conditions.
What It Means for Treatment
Recognizing the overlap matters clinically. Stimulant medications that help many ADHD patients can produce paradoxical or adverse effects in autistic individuals, making one-size-fits-all prescribing risky. Neuroimaging studies show that co-occurring autism and ADHD creates distinct brain-structure patterns that are not merely additive—suggesting the combination requires its own treatment strategies.
Researchers increasingly argue for a dimensional approach: assessing specific symptom profiles rather than assigning a single diagnostic label. This shift could lead to more individualized combinations of medication, behavioral therapy, and environmental support, tailored to each person's unique neurological profile rather than a checkbox on a diagnostic form.
