Autism is mainly about differences in social communication and a need for routine, while ADHD is mainly about inattention, hyperactivity and impulsiveness. They often overlap, and a child can have both (AuDHD).
The core difference
Both are lifelong differences in how the brain develops, and your child is born with them — neither is an illness. The clearest single contrast is what your child does with newness. A child with ADHD tends to chase novelty and act on impulse: bored quickly, drawn to whatever is most stimulating right now, making fast decisions without weighing them up. An autistic child tends to do the opposite — craving routine, predictability and structure, and finding sudden change hard. So the question to sit with is less “how busy is my child” and more “does my child seek out change or steady themselves against it.”
Autism and ADHD side by side
| What you might see | Autism | ADHD |
|---|---|---|
| Social communication | Differences in reading social cues, eye contact, and back-and-forth conversation | Interrupting, talking over others, missing cues because attention has drifted |
| Routine vs novelty | Craves routine and structure; finds change and surprise distressing | Seeks novelty and stimulation; bored by repetition; acts on impulse |
| Attention | Deep, sustained focus on areas of interest | Hard to sustain attention on dull tasks; easily distracted |
| Movement | Repetitive movement (stimming) that soothes or expresses feeling | Restlessness and hyperactivity driven by a need for more input |
| Often shared | Sensory differences, trouble with planning and organising (executive function), intense focus on a favourite thing (hyperfocus), and big emotional swings | |
They overlap far more than parents are told
The story parents usually hear is “it's one or the other.” It often isn't. The UK autism research charity Autistica reports that around 28% of autistic children also meet the criteria for ADHD, and around 21% of children with ADHD are also autistic. When both are present, it is sometimes called AuDHD. This matters because before the diagnostic manual known as DSM-5 was published in 2013, clinicians were not allowed to give both diagnoses to the same person — one ruled out the other. DSM-5 removed that rule, so a child can now be formally diagnosed with both. Some older guidance, and some clinicians trained under the old rule, still frame the two as mutually exclusive, which is how one diagnosis can end up masking the other.
Where the law comes from
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This page is general information, not clinical or legal advice.