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Differences between ASD and Down Syndrome

Autism Spectrum Disorder and Down Syndrome are two different conditions with shared characteristics.

Differences between ASD and Down Syndrome

Autism Spectrum Disorder (ASD) and Down Syndrome (DS) are complex and lifelong conditions. Although the two conditions have certain qualities in common, they have different causes, symptoms, treatments, and management. The two conditions can also occur together, with about 20% of people with Down syndrome who are also autistic. This fact, together with their commonalities, causes some to confuse the two conditions. This article will be sharing more on the differences between ASD and Down Syndrome.

Autism Spectrum Disorder

Autism is a neurodevelopmental condition that impairs a person's ability to communicate verbally, interact socially, and behave in certain ways. It is a lifelong developmental disorder that affects how people perceive their environment and relate to others. People with autism may have quite distinct ways of hearing, feeling, and interacting with others.

Some examples of common social communication deficits in people with ASD include little or no desire to share one's interests with others, difficulty understanding their feelings as well as those of others, having trouble maintaining eye contact, having trouble making friends, rigid or robotic-sounding speech and an inability to understand abstract concepts. Additionally, people with ASD may tend to have ​​repetitive habits and constrained interests.

It is important to note that individuals with autism exhibit a wide variety of characteristics and can appear very different from one another.

Down Syndrome

Down syndrome (DS or DNS) is a chromosomal disorder which is caused by the third copy of chromosome 21. Most people with Down syndrome exhibit cognitive abilities comparable to those of 8 and 9 year olds. They may experience speech and language delays as well as learning and memory problems. Some people, however, can live quite typical lives. It occurs more frequently in pregnancies with mothers age 35 or older.

Individuals with Down syndrome might have varying degrees of severity. It might lead to developmental delays, intellectual impairment, and lifelong learning difficulties. The severity of the illness will determine whether the person also has other health issues, such as heart defects, defects of the GI tract, sleep apnea, immune system disorders, spinal problems, and weight management problems. Normal symptoms of the illness include a slower rate of growth, reduced muscle tone, and a lower IQ.

Moreover, most individuals with Down syndrome have distinct facial features that may include: a short neck, tilted eyelids, weak muscle tone, flat face, small head, short hands with single palm crease, small hands and feet along with small fingers and toes. These distinct features can make it possible to spot people with Down Syndrome by looking at their physical characteristics.

Differences between the two

Despite the common traits that they share such as facing similar developmental and speech delays, ASD and Down Syndrome differ in cause, diagnosis, symptoms and physical traits.

1. Cause

There is no clear cause for Autism Spectrum Disorder and the causes may be a combination of genetic and environmental factors. On the other hand, there is a clear chromosomal cause of Down Syndrome which is partial or complete trisomy of Chromosome 21.

2. Diagnosis

Autism may be diagnosed in early childhood by a child psychiatrist or psychologist whereas Down Syndrome can be diagnosed in the womb through prenatal testing before birth or immediately after birth through direct observation.

3. Symptoms

Although ASD and Down Syndrome share several characteristics, there are some areas in which they differ. Here are some examples:


Down Syndrome

May have difficulties understanding social cues and communicating in social situations.

Understand social cues and participate in social communication more easily.

May not follow standard language learning patterns. Some individuals do not speak.

The language development of people with DS is similar to that of typically developing children.

May have minimal or no use of gestures.

Use of signs and symbolic gestures.

May engage more in parallel play.

Able to engage easily with joint attention.

Wide range of intellectual abilities – from severe delays to gifted abilities.

Learn and develop more slowly.

4. Physical Traits

Autism does not affect the physical traits of a person whereas Down Syndrome is associated with distinct physical features as mentioned above.


In short, ASD and Down Syndrome are two distinct conditions ranging from their cause, diagnosis, symptoms and physical traits. Being aware of the differences between the two allows us to appreciate the uniqueness of individuals with these conditions better and not define them by their conditions or their symptoms.

Written by: Hayley


Desai, S. S. (1997). Down syndrome: a review of the literature. Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontics, 84(3), 279-285.

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Fotedar -Dr, D. (2022, February 4). Difference Between Autism and Down Syndrome. Difference Between Similar Terms and Objects.

Lord, C., Cook, E. H., Leventhal, B. L., & Amaral, D. G. (2013). Autism spectrum disorders. Autism: The Science of Mental Health, 28(2), 217.

Martin, G. E., Klusek, J., Estigarribia, B., & Roberts, J. E. (2009). Language characteristics of individuals with Down syndrome. Topics in Language Disorders, 29(2), 112–132.

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