Autism spectrum disorder (ASD) is a group of developmental disabilities that impair someone’s ability to socialize and communicate. According to the Centers for Disease Control and Prevention, ASD affects 1 in 59 American children.

These neurodevelopmental (brain) disorders are sometimes detectable before one year of age, but they often go undiagnosed until much later.

Most children with autism are diagnosed after the age of three. Early intervention is the most effective treatment, so any signs of autism in three-year-old children should be evaluated by a professional.

The symptoms of ASD vary from person to person, falling along a wide range of severity, known as a “spectrum.” Children with ASD typically interact and communicate differently than others.

They also learn and think differently than others. Some are greatly challenged, requiring significant assistance in daily life, while others are high-functioning.

There is no cure for autism, but with treatment, symptoms can improve.

In some children, autism symptoms are evident in the first few months of life. Other children don’t display symptoms until the age of two. Mild symptoms can be difficult to spot and may be mistaken for a shy temperament or the “terrible twos.”

You may see some of the following signs of autism in three-year-old children.

Social skills

  • doesn’t respond to name
  • avoids eye contact
  • prefers playing alone to playing with others
  • doesn’t share with others, even with guidance
  • doesn’t understand how to take turns
  • isn’t interested in interacting or socializing with others
  • doesn’t like or avoids physical contact with others
  • isn’t interested or doesn’t know how to make friends
  • doesn’t make facial expressions or does make inappropriate expressions
  • can’t be easily soothed or comforted
  • has difficulty expressing or talking about feelings
  • has difficulty understanding other people’s feelings

Language and communication skills

  • has delayed speech and language skills (falling behind peers)
  • repeats words or phrases over and over
  • doesn’t answer questions appropriately
  • repeats what others say
  • doesn’t point to people or objects or doesn’t respond to pointing
  • reverses pronouns (says “you” instead of “I”)
  • rarely or never uses gestures or body language (for example, waving)
  • talks in a flat or sing-song voice
  • doesn’t use pretend play (make believe)
  • doesn’t understand jokes, sarcasm, or teasing

Irregular behaviors

  • performs repetitive motions (flaps hands, rocks back and forth, spins)
  • lines toys or other objects up in an organized fashion
  • gets upset, frustrated by small changes in daily routine
  • plays with toys the same way every time
  • has odd routines and gets upset when not allowed to carry them out (such as always wanting to close doors)
  • likes certain parts of objects (often wheels or spinning parts)
  • has obsessive interests
  • has hyperactivity or short attention span

Other potential autism signs

  • has impulsivity
  • has aggression
  • self-injures (punching, scratching themselves)
  • has persistent, severe temper tantrums
  • has irregular reaction to sounds, smells, tastes, looks, or feels
  • has irregular eating and sleeping habits
  • shows lack of fear or more fear than expected

Having any one of these signs or symptoms may be normal, but having several of them, particularly with language delay, should prompt more concern.

The symptoms of autism are generally the same for both boys and girls. However, because autism is diagnosed in boys far more often than girls, classic symptoms are often described in a skewed manor.

For example, an excessive interest in trains, the wheels on trucks, or strange dinosaur trivia is often very noticeable. A girl who doesn’t play with trains, trucks, or dinosaurs might display less noticeable behaviors, like arranging or dressing dolls in a particular way.

High-functioning girls also have an easier time mimicking average social behaviors. Social skills may be more innate in girls, which can make impairments less noticeable.

Autism disorders fall along a spectrum of mild to severe. Some children with ASD have advanced learning and problem-solving skills, while others require daily living assistance.

According to the American Psychiatric Association’s diagnostic criteria, there are three levels of autism that are defined by how much support a person requires.

Level 1

  • shows little interest in social interactions or social activities
  • has difficulty initiating social interactions
  • has difficulty maintaining a back and forth conversation
  • has trouble with appropriate communication (volume or tone of speech, reading body language, social cues)
  • has trouble adapting to changes in routine or behavior
  • has difficulty making friends
  • is able to live independently with minimal support

Level 2

  • has difficulty coping with change to routine or surroundings
  • has significant lack verbal and nonverbal communication skills
  • has severe and obvious behavior challenges
  • has repetitive behaviors that interfere with daily life
  • has unusual or reduced ability to communicate or interact with others
  • has narrow, specific interests
  • requires daily support

Level 3

  • has nonverbal or significant verbal impairment
  • has limited ability to communicate, only when require needs to be met
  • has very limited desire to engage socially or participate in social interactions
  • has extreme difficulty coping with unexpected change to routine or environment
  • has great distress or difficulty changing focus or attention
  • has repetitive behaviors, fixed interests, or obsessions that cause significant impairment
  • requires significant daily support

There is no blood or imaging test that can be used to diagnose ASD. Instead, doctors diagnose children with autism by observing their behavior and monitoring their development.

During an exam, your doctor will ask you questions about your child’s behavior to see whether they meet standard developmental milestones. Talking and playing with toddlers helps doctors recognize signs of autism in a three-year-old.

If your three-year-old is showing signs of autism, your doctor may recommend seeing a specialist for a more compressive examination.

An examination might include medical tests and should always include screenings for hearing and vision. It will also include an interview with the parents.

Early intervention is the best treatment for ASD. Early treatment can significantly improve the outcome of your child’s disorder. Under the Individuals with Disabilities Education Act (IDEA), all states are required to provide an adequate education to schoolchildren.

Most states also have early intervention programs for children three and younger. Consult this resource guide from Autism Speaks to see what services are available in your state. You can also call your local school district.

Autism questionnaire

The Modified Checklist for Autism in Toddlers (M-CHAT) is a screening tool that parents and doctors can use to help identify children who are at risk of autism. Organizations like Autism Speaks offer this questionnaire online.

Children whose scores suggest an elevated risk of autism should make an appointment with their pediatrician or with a specialist.

Signs of autism are typically apparent by the age of three. Early intervention leads to improved outcomes, so it’s important to get your child screened as soon as possible.

You may want to begin with your pediatrician or make an appointment with a specialist (you may need a referral from your insurance company).

Specialists who can diagnose children with autism include:

  • developmental pediatricians
  • child neurologists
  • child psychologists
  • child psychiatrists

These specialists can guide you in developing a treatment plan for your child. You may also want to reach out to see what government resources are available to you.

You can start by contacting your local school district (even if your child isn’t enrolled there). Ask them about support services in your area, such as early intervention programs.