Autism Vs Down Syndrome – How to Tell These Disorders Apart

Last Updated on July 11, 2025 by John Hookway

Autism vs Down Syndrome are two distinct conditions with different causes, appearances, and behaviors. Autism typically presents challenges with communication and social interactions, while Down syndrome is characterized by unique physical features and developmental delays.

Understanding the differences between Autism vs Down Syndrome is crucial for providing the right support. Proper care and tailored educational approaches can significantly improve the quality of life for children with either condition.

Recent research highlights that children with both Autism vs Down Syndrome require specialized attention.

Families and caregivers who recognize these distinctions are better equipped to seek appropriate resources and assistance. A comparison of Autism vs Down Syndrome reveals these important differences.

Autism Overview

Autism Spectrum Disorder (ASD) is a condition that lasts for life. It affects how the brain develops. The DSM-5 and ICD-11 both describe autism by certain main features.

These features change how a person acts, talks, and behaves. The DSM-5 uses “Autism Spectrum Disorder” to group older terms like Asperger syndrome and classic autism. Autism includes:

• Ongoing problems with talking and social skills.
• Doing the same things or having the same interests over and over.
• Signs usually start when a child is young, but may be noticed more as they grow.

ICD-11 also says that sensory differences are important in autism. Both systems agree that autism can look different for each person. Some people need a lot of help, while others need less.

Features

Autism has many different features. These features are not the same for everyone. Most people with autism have trouble in two main areas:

• Talking and social skills
• Repetitive actions or interests

Some common features are:

• Not making eye contact or avoiding it
• Having trouble with facial expressions or body language
• Speaking in a flat or unusual voice
• Repeating movements like flapping hands or rocking
• Liking routines and getting upset if they change
• Focusing a lot on certain topics or things
• Being very sensitive to sounds, lights, or how things feel

Many people with autism also have other health issues. These can be anxiety, sleep troubles, seizures, or problems with senses. Signs of autism often show up by 18 months old, but can change as the person grows.

Social and Communication

Having trouble with social skills and talking is a big part of autism. People with autism may find it hard to start or keep a conversation.

They might not look at people or use normal gestures. This can make it hard to talk with others. Some common problems are:

• Speaking late or not at all
• Using only a few words or not speaking clearly
• Repeating what others say (echolalia)
• Not understanding jokes or sarcasm
• Having trouble with facial expressions, body language, or tone of voice
• Not knowing social rules, like taking turns when talking
• Finding it hard to make or keep friends

Note: Being very sensitive to loud sounds or bright lights can make social times harder. These problems can make someone feel left out or cause confusion with friends.

People with autism may not understand how others feel or think. This makes it hard to act the right way in social situations.

Every person with autism is different. Their social and talking skills can be very limited or very strong, depending on the person.

Behaviors

Kids and adults with autism often act in special ways. These actions help doctors and families spot autism early. Many of these actions are different from what most people do.

• Repetitive Movements: People with autism may repeat actions a lot. They might flap their hands or rock back and forth. Some spin things or flick their fingers. These movements can happen many times and look odd to others.
• Fixated Interests: Some people focus on one thing for a long time. This interest can last for months or even years. For example, a child might learn all about trains. Some only collect blue cars. These interests can take up most of their time.
• Compulsions and Rituals: Many people with autism like routines. They may line up toys in a certain way. Some want to take the same path to school every day. If routines change, they may get upset or anxious.
• Self-Injury: Some people may hurt themselves. This can mean banging their head or biting their skin. Sometimes they scratch themselves. These actions often happen when they feel stressed or cannot say what they need.
• Sensory Sensitivities: People with autism may react strongly to sounds or lights. Loud noises or bright lights can hurt. Some cover their ears or stay away from certain places because of this.
• Insistence on Sameness: Many want things to always be the same. They may eat the same food every day. Some wear the same clothes all the time. Changes in routine can make them feel angry or stressed.
• Difficulty with Flexibility: It can be hard to handle new things. Changing from one activity to another may cause meltdowns or make them pull away.

Note: These actions are not just habits. They are part of how autism affects the brain and body. These actions are often stronger and more focused than normal childhood routines.

Social and talking problems also show in behavior. Many people with autism have trouble making eye contact.

Some do not understand body language. They may repeat words or phrases. This is called echolalia. Some find it hard to join talks or get jokes and sarcasm.

A table below shows common behaviors in autism:

These actions can cause stress if stopped. Families and teachers can help by learning about these patterns.

They can make safe and helpful spaces. Knowing these actions early helps people with autism get better support and care.

Down Syndrome Overview

Down syndrome is a genetic condition. It changes how the brain and body grow. People with Down syndrome have an extra chromosome 21.

This means they have 47 chromosomes, not 46. The extra chromosome affects how they grow and learn. Down syndrome usually does not run in families. It happens because of a random change early in development.

Doctors call this change “trisomy 21.” The condition causes both intellectual and physical differences. Most people with Down syndrome have mild or moderate intellectual disabilities.

They often have developmental delays. Leading health groups, like the National Institutes of Health, agree with this definition.

Features

Down syndrome is the most common chromosomal disorder. It causes intellectual disability. The extra chromosome 21 affects almost every organ system.

Children with Down syndrome often grow slower. Their bones may develop later than usual. Teeth may come in late too. The condition causes many features, but not everyone has all of them. The gene-dosage effect explains why these features happen.

Too many copies of some genes on chromosome 21 cause these changes. Doctors see that children with Down syndrome may have heart problems. They may also have hearing or vision issues and weak muscles. Some may get digestive or thyroid problems.

Adults with Down syndrome have a higher risk of early Alzheimer’s disease. Each person’s experience is different, but the condition always includes some of these features.

Physical Traits

Doctors can often spot Down syndrome by looking at certain traits. These traits show up in many body parts.

The table below lists some common physical signs:

Doctors use these traits and genetic tests to confirm Down syndrome. Not everyone has all these traits, but most have several. These signs help families and doctors spot Down syndrome early. This helps them plan for the right support.

Intellectual Abilities

People with Down syndrome think and learn in different ways. Most have trouble with thinking skills. Their IQ scores are between 30 and 70.

This is lower than most people without Down syndrome. They learn new things more slowly. As they get older, the difference between them and other kids gets bigger.

Kids and adults with Down syndrome have a special way of learning. They find language harder than other tasks. Speaking and making sentences is very hard for them.

Many can understand words before they can say them. Reading and writing take longer to learn. They are better at things like puzzles or shapes. Many studies show this pattern.

Memory is also affected in Down syndrome. Remembering things they hear is hard. They are better at remembering things they see. Planning and staying organized is also tough. These problems make learning new things harder.

Moving their bodies can be slow to develop. Small tasks like writing or buttoning shirts are hard. Big movements like walking or jumping are also slow. Physical and occupational therapy can help them get better at these skills.

Adaptive behavior means how well someone does daily tasks. People with Down syndrome may need help with self-care and talking. Their daily skills are often like their IQ scores. Some can do many things alone, but others need more help.

Note: People with Down syndrome have more trouble talking than doing other things. They often understand more than they can say.

Each person with Down syndrome learns in their own way. Some learn fast, others need more time and help. Early help and special teaching can make a big difference.

Families, teachers, and therapists are important for their learning. Everyone with Down syndrome has things they are good at and things that are hard. With the right help, many can have happy and successful lives.

Autism Vs Down Syndrome

Autism and Down syndrome start in different ways. Down syndrome always happens because of a genetic change.

People with Down syndrome have one extra chromosome 21. This extra chromosome causes how they look and learn.

Down syndrome does not come from things in the environment. It happens by chance when cells divide.

Autism has more reasons behind it. Many things can cause autism. Some cases are linked to changes in single genes.

Examples are Fragile X syndrome or changes in genes like CHD8 and SHANK3. Sometimes, parts of chromosomes are missing. But these gene changes only explain some cases. Things in the environment can also raise the risk.

These include infections during pregnancy, some medicines, pollution, older parents, and babies born early. Scientists think both genes and the environment work together to affect autism risk.

Here is a table that shows how the causes are different:

Note: Down syndrome always has the same genetic cause. Autism can have many different causes from genes and the environment.

Physical Differences

Physical differences between Autism and Down syndrome are easy to see. Kids with Down syndrome often look alike in some ways.

They may have eyes that slant up, a flat nose, small ears, and a tongue that sticks out. Their hands and feet are smaller than usual. They may grow slower and have heart problems.

Autism does not have special physical features. Doctors cannot tell if someone has autism just by looking. Kids with autism may have health problems like trouble sleeping or stomach pain.

But these problems are not only found in autism. Some studies show kids with autism may have higher body weight and sit taller. Kids with Down syndrome are often more flexible.

Here are some common physical differences:

Down syndrome:

• Eyes slant up and look almond-shaped
• Flat nose and small ears
• Tongue sticks out
• Small hands and feet
• Grow slower than other kids
• May have heart problems

Autism:

• No special physical features
• May have other health problems (not just in autism)
• May have higher body weight and less flexibility

Doctors use how someone looks to help find Down syndrome, but not autism.

Intellectual Differences

Intellectual skills are another big difference between Autism and Down syndrome. Down syndrome almost always causes mild or moderate intellectual disability.

Most people with Down syndrome have IQs between 50 and 70. They learn slower and need more help at school and home.

Autism can look very different in each person. Some people with autism have severe intellectual disabilities. Others have normal or even high intelligence.

About one out of three people with autism have intellectual disabilities. Many others have average or high IQs. Some are very good at things like math or memory but have trouble with social skills.

This table shows the differences in intellectual skills:

Autism and Down syndrome are most different in how people learn. Down syndrome usually means steady learning problems. Autism can mean many different levels of ability.

Social and Language

Social and language skills are very different in Autism vs Down Syndrome. Kids with Down syndrome like being with people.

They often smile and act friendly. Even if they talk late, they use hand signs and faces to share how they feel. Many can understand more words than they can say. Some use pictures or signs to tell others what they need.

Kids with autism have more trouble with talking and being social. They may not look at people when talking. Some do not use hand signs or faces. Some kids with autism do not talk at all. Others repeat words or phrases over and over.

Their voices may sound flat or odd. Jokes and body language are hard for them to understand. Many like to play alone and do not join group games.

The table below shows the main ways social and language skills are different:

Kids with Down syndrome use hand signs and faces to help them talk. Kids with autism may have trouble with both talking and using signs. Speech therapy helps both, but the help is not the same for each group.

Behaviors

How kids act is also different in Autism vs Down Syndrome. Kids with autism often do the same actions again and again.

They may flap their hands or rock back and forth. Some talk a lot about one thing they like. Changes in their daily routine can make them upset. Loud sounds, bright lights, or certain touches can bother them a lot.

Kids with Down syndrome do not usually repeat actions like kids with autism. They may not pay attention for long or act without thinking.

But they do not focus on one thing for a long time. Most can handle changes in their day better. They like to hug and play with others.

Here is a table that compares how kids act:

Kids with autism often have stronger reactions to sounds, lights, or touch. Both groups may need help with daily tasks, but the reasons are not the same.

Diagnosis Timing

When doctors find out about Autism vs Down Syndrome is different. Down syndrome can be found at birth or even before birth.

Doctors use special tests to check for it. The way kids with Down syndrome look is often easy to see right away.

Autism is usually found later. Signs can show up by 18 months old. But many kids are not diagnosed until they are 2 to 4 years old or even older.

If a child has both Down syndrome and autism, autism may be found even later. This is because some signs of autism look like other problems seen in Down syndrome. Doctors use special checklists and tools to help tell them apart.

Key facts about when doctors find out:

• Down syndrome is often found at birth or before birth.
• Autism is usually found between 18 months and 4 years, but sometimes later.
• If a child has both, autism may be found late because some signs are the same.
• Early checks and expert help make sure kids get support as soon as possible.

Finding out early is important for both conditions. It helps families start therapy and support early, which can help kids do better.

Overlapping Features

Shared Challenges

Autism and Down syndrome are different, but some problems are the same. Some kids with these conditions have trouble with talking and acting with others.

They may not be able to say what they want or understand what people mean. Both groups often need extra help to learn how to talk and make friends. Families see that their children may not use words or gestures well.

They may not get jokes or body language. Social times can be confusing. Making friends can be hard and take more time.

Kids with both conditions may do things over and over, like hand-flapping or focusing on one thing. These actions are seen in both groups, but they happen more in autism.

The table below shows where these problems are the same:

Teachers and caregivers should look for these shared problems. Helping early can make talking and social skills better.

Co-occurrence

Some kids have both autism and Down syndrome at the same time. This is called “co-occurrence.” Having both makes things more complicated.

It can be harder for doctors to figure out what is going on. Studies show that autism happens more often in kids with Down syndrome than in other kids.

The table below shows how often both happen together:

These studies show that autism and Down syndrome happen together in about 13% to 42% of cases. In most people, autism only happens in about 1.85%. This means kids with Down syndrome are more likely to also have autism.

When a child has both, they need special help. Doctors work together to find out what each child needs. Families do better when they know early and get the right help. This helps them find good therapies and support.

Finding both conditions early helps kids do better. Support should fit each child’s own needs and strengths.

Diagnosis and Support

Diagnosis Methods

Doctors use different ways to find out if a child has autism or Down syndrome. Down syndrome is often found before or right after birth.

Doctors might use ultrasound or blood tests during pregnancy to look for signs. After the baby is born, doctors check the baby’s body and do a genetic blood test. The test shows if there is an extra chromosome 21.

Autism is usually found later, when a child is between 18 months and 4 years old. Doctors listen to parents and watch how the child acts.

They use special checklists like the Modified Checklist for Autism in Toddlers (M-CHAT) and the Social Communication Questionnaire (SCQ). These checklists help find early signs.

Sometimes, these tools say a child has autism when they do not, especially if the child has Down syndrome. This is because some behaviors are the same in both.

A group of experts does more tests, like the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised (ADI-R).

These tests let doctors watch the child and talk to parents in a careful way. Doctors also use the DSM rules to decide if a child has autism. Using many tools and expert opinions helps doctors make the best decision.

New genetic tests, like chromosomal microarray analysis and whole exome sequencing, help doctors find genetic reasons for autism. These tests help doctors find answers sooner and give care that fits each child. For Down syndrome, genetic testing is still the best way to know for sure.

Support Options

Kids with autism and Down syndrome do best when they get help early. Each child needs a plan made just for them.

A team works together to help, including therapists, doctors, teachers, and families. The main goal is to help every child do their best.

Key therapies and supports include:

• Speech and Language Therapy: This helps kids talk and understand others. Some kids use AAC devices, like picture boards or tablets, if talking is hard.
• Occupational Therapy: This helps kids learn daily skills and handle things that bother their senses.
• Behavioral Therapy: Applied Behavior Analysis (ABA) is used a lot for autism. It teaches social skills and helps with behavior. ABA is also being tried for Down syndrome.
• Physical Therapy: This helps kids move better. It is very important for kids with Down syndrome.
• Social Skills Training: This teaches kids how to talk to others and handle feelings.
• Medical Management: Doctors check and treat health problems, like heart or thyroid issues, that are common in Down syndrome.

A table below shows the main support options:

Families can get help from groups like the Autism Society and National Down Syndrome Society. Local groups, schools, and community centers also have resources and training. Getting help early and having support at home and school helps kids grow and learn.

Autism and Down syndrome are not the same. They have different causes and look different. Kids with these conditions learn in their own ways.

Finding out early helps kids get the right help. Therapies can make talking, making friends, and being independent easier.

Each child needs support that fits them. Parents and teachers can help a lot. Support should match the family’s culture and needs. This helps kids do better in life.

• Getting help early lowers stress for families. It also helps kids do their best.
• Doctors and experts check each child to give the best care.

Every child is special. With care and support, they can do well and have a happier life.

FAQ

What is the main difference between autism and Down syndrome?

Autism changes how someone talks and gets along with others. Down syndrome is caused by a change in genes. It leads to special looks and slower learning. Autism does not have special looks, but Down syndrome does.

Can a person have both autism and Down syndrome?

Yes, some people can have both at the same time. Doctors call this “co-occurrence.” Kids with Down syndrome are more likely to also have autism than other kids.

How do doctors diagnose autism and Down syndrome?

Doctors use genetic tests to find Down syndrome, usually right after birth. They find autism by watching how a child acts and using checklists. Autism is often found when kids are 2 to 4 years old.

Do children with autism and Down syndrome need different therapies?

Every child needs their own plan.
Kids with autism often need help with behavior and talking. Kids with Down syndrome need help moving and learning daily skills. Some therapies are the same for both.

Are there early signs parents should watch for?

Parents should look for late talking, trouble making friends, or doing the same actions over and over. For Down syndrome, special looks like almond-shaped eyes or weak muscles may show up at birth.

Can children with autism or Down syndrome go to regular schools?

Many kids with autism or Down syndrome go to regular schools. They might need extra help or special classes. Schools make plans to help each child learn.

Where can families find support and resources?

Families can get help from groups like the Autism Society or National Down Syndrome Society. Local schools, doctors, and community centers also give support. Support groups help families meet others with the same challenges.