Is there a connection between ASD and Down syndrome?

We’ve previously looked into connections between autism and diabetes, but what about autism and Down syndrome?


So many people are diagnosed with both, it’s an area that deserves some investigation. Let’s take a look at the two conditions and how they might overlap.

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Differences between autism and Down syndrome

First of all, we need to establish what sets autism and Down syndrome apart:



Autism is a neurodevelopmental difference that can affect a person’s abilities in behaviour, social interaction, and language. While autistic behaviours can be identified in children as young as 2 years old, it’s impossible to tell if a person is autistic just by looking at them.

Down syndrome

Down syndrome is a common genetic disorder, caused by a difference in chromosomes. Unlike autism, Down syndrome can be detected via a blood test and causes recognisable physical traits. It also affects behaviour, often causing individuals to learn more slowly.


Possible connections between autism and Down syndrome

According to a 2015 study, it appears that people with any sort of genetic disorder are more likely to have autism. Rett’s syndrome, in particular, had the highest correlation, with 61% of subjects also being autistic.


Down syndrome was much lower at 16-18%, but this is still significant enough to draw a connection. As a result, it does appear that having Down syndrome increases a person’s chances of having autism – though it isn’t highly likely that this will be the case.


Seeking and managing a dual diagnosis

Autism and Down syndrome come with their own unique challenges, and the same can be said for a combination of the two.


Compared to people with Down syndrome but not autism, people with both are more likely to have:

  • Difficulty communicating
  • Sensory sensitivities
  • Repetitive behaviours
  • Cognitive challenges
  • Slower processing speeds

And compared to people with autism but not Down syndrome, people with both are more likely to have:

  • More social interest
  • More significant cognitive challenges
  • Slower processing speeds (that may be misinterpreted as stubbornness)
  • Less severe repetitive behaviours


If you suspect that a person in your care with Down syndrome also has autism, it’s a good idea to seek a formal diagnosis. This can help both you and any health professionals to give them the support they need.

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Giving autistic and non-verbal children a voice

Whether they have Down syndrome or not, autistic and non-verbal children can struggle to express themselves. We believe communication should be free for everyone, so we created app2vox: a downloadable app packed with helpful tools like intuitive icons, text-to-speech, and phrase building.


Take a look at how the app works for more information, and register your interest to stay on top of the latest updates. If you’d like to carry on reading, we have other useful articles just like this one over in our resources.