The Difference Between Down Syndrome and Autism Explained

Down Syndrome often gets mistaken for Autism. This confusion is due to the fact that people with these conditions can show what seem very similar symptoms to the untrained eye. However, Down Syndrome and Autism are very different from each other and their symptoms can vary significantly.

What’s the Main Difference Between Down Syndrome and Autism?

Down Syndrome has prominent physical features, including a short neck and slanted eyes, while Autism does not. While both conditions can affect development, Autism has a more significant direct impact on the ability of autistic people to socialize and communicate. 

This article will explain what Autism and Down Syndrome are, and the causes of both conditions. If you think these conditions are similar, keep reading to learn more about what makes each condition unique.

What Is Autism Spectrum Disorder?

Autism, also called Autism Spectrum Disorder (ASD), is a developmental condition that affects an individual’s perceptions. Autistic people have difficulty grasping interpersonal skills for socializing, communicating, and interacting with others.

Autism is a developmental condition that can be diagnosed very early in a person. Such a diagnosis can only be made by a psychologist or psychiatrist. There are also given characteristics that autistic persons tend to possess, ranging from narrowed interests to repetitive behaviors.

In extreme conditions, there could also be an intense difficulty in communication and social interaction. Autism Spectrum Disorder has a wide range of symptoms and multiple levels of severity. This is why the disorder is described as a “spectrum.”

Causes of Autism or Autism Spectrum Disorder

According to researchers, there is no primary known cause of ASD besides genetics. Although genetics is often the reason why a person is born with ASD, there are also a few non-genetic factors that can cause autism. These factors range from:

  • Extremely low birth weight.
  • Having Down Syndrome or related conditions.
  • Late maternal or paternal birth.
  • Metabolic imbalances.
What is Autism Spectrum Disorder - Mother is Training Her Autistic Child
What is Autism Spectrum Disorder – Mother is Training Her Autistic Child

What Is Down Syndrome?

Down Syndrome, also called Trisomy 21, is a chromosomal disorder in individuals born with an additional chromosome (chromosome 21). When present in the body, this extra whole or partial chromosome results in Down Syndrome. 

DNA is the essential building block of the human system. It’s the material that codes for our genes. Chromosomes, on the other hand, are structures found in the nuclei of cells that carry pieces of DNA. In humans, each regular body cell, called a somatic cell, normally contains 23 pairs of chromosomes, making a total of 46.

Our bodies depend on this exact number of chromosomes—no more and no fewer—to function effectively. Therefore, having an extra pair of chromosomes, a person with Down Syndrome will have several physical and mental challenges.

There are characteristic physical and developmental features of individuals with Down Syndrome. These include easily distinguishable facial features and delayed intellectual growth caused by mildly to moderately low IQ.

Causes of Down Syndrome

There is no single explanation for why Down Syndrome occurs. Science hasn’t quite narrowed down how many exact factors play a significant role in the existence of Down Syndrome in an individual either.

However, there are a few causes and risk factors that could explain the occurrence of Down Syndrome.

  • An extra Chromosome 21: About 95% of people with Down Syndrome have an extra Chromosome 21. That’s why we can safely assume that this extra bit is the cause of the physical and mental challenges faced by people with Down Syndrome.
  • Late maternal birth: Research has shown that women older than 35 are generally more likely to give birth to children with Down Syndrome than younger women.
What Is Down Syndrome - Mother is Teaching Her Daughter with Down Syndrome
What Is Down Syndrome – Mother is Teaching Her Daughter with Down Syndrome

Differences Between Down Syndrome and Autism

Autism or Autism Spectrum Disorder (ASD) and Down Syndrome are both classified as developmental conditions, but they are different.

Both have different causes, symptoms, treatments, and management methods. Here are some of the major differences between Autism Spectrum Disorder and Down Syndrome:

  • Patients with Down Syndrome have distinctive physical characteristics, including facial features like a small head, short neck, and slanted eyelids. With Autism, on the other hand, no physical traits have yet been detected.
  • A person with Autism Spectrum Disorder may suffer social withdrawals, have little or no interest in communicating with others, and show gross indifference. Down Syndrome, on the other hand, doesn’t directly affect the person’s interest in other people.
  • People with Autism Spectrum Disorder usually have social disabilities that include a lesser capacity for language use. With Down Syndrome, on the other hand, this disability only affects people with severe cases. Those with mild to moderate levels often have intellectual abilities that are fairly equal to their developmental levels.
  • Autistic people are often limited to verbal communication. When their ability to speak is affected, they make little to no attempt to use other modes of communication. Those with Down Syndrome often support their verbal language, whether limited or not, with symbolic gestures.
  • Depending on the severity, people with Autism Spectrum Disorder don’t acknowledge other people or show interest in them. People with Down Syndrome are often better at acknowledging others by making eye contact, responding when they are spoken to, or repeating things others say.

Frequently-Asked Questions On Down Syndrome and Autism

Can a Person Have Down Syndrome and Autism at the Same Time?

Yes, a person can have Autism Spectrum Disorder and Down Syndrome at the same time. People who have both co-existing conditions are said to have a dual diagnosis.

Over the past few years, the number of children diagnosed with both Down syndrome and Autism has noticeably increased.

According to the Global Down Syndrome Foundation, “Current research suggests between 8 and 18 percent of individuals with Down syndrome may also have autism.”

How Are Down Syndrome and Autism Similar?

A few similar characteristics of Autism and Down Syndrome are:

  • Difficulty in hearing, leading to a reduced ability to respond to their names.
  • Poor sight.
  • Limited verbal expression and the use of stereotyped, repetitive statements.
  • Limited ability to hold a conversation.
  • Insistence on routine behavior.


Autism and Down Syndrome are both challenging developmental conditions, but they can be very different from each other. The agitation, nervousness, anxiety, insomnia, or disturbed sleep in people with these conditions can be a lot to handle.

If you think you may have this condition or have trouble caring for someone who has been diagnosed, you should speak with a doctor for help.

Thanks for reading!

If you enjoyed this article about down syndrome and autism, you may want to read: Is Mental Health a Disability? 10 Serious Conditions To Know, and Is Rewatching Shows a Sign of Mental Illness?.


M.D Mark D. - Healthline Gate Health and Medical Articles Author

About The Author

M.D Mark D. is a Health and Wellness professional writer. Mark has authored many health articles around the following topics: Men’s Health, Women’s Health, Fitness, Nutrition, Pets Health, Mental Health, Medicine, and Supplements.

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