Merck Manual

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Quick Facts



The Manual's Editorial Staff

Last full review/revision Oct 2019| Content last modified Oct 2019
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What is autism?

Autism is a brain disorder that affects how people interact with other people and communicate.

People with autism have trouble talking with and relating to other people. They also have unusual behaviors. The word autism refers to a whole range (spectrum) of related problems. So doctors call these autism spectrum disorders.

  • Children with autism typically have unusual, repetitive behaviors, have limited interests, and follow rigid routines

  • Autism starts in childhood and is usually noticeable before age 2

  • Children with mild symptoms may not be diagnosed until they're school-age

  • Autism is different from low intelligence (intellectual disability)

  • Autism isn't caused by vaccines (shots) or bad parenting

What are the symptoms of autism?

Children with autism have many different symptoms. And how severe the symptoms are varies. However, the different symptoms always involve two things:

  • Trouble communicating and interacting with people

  • Unusual, repetitive behaviors, interests, or activities

These symptoms begin at a young age, often when your child is just a baby. However, you and your doctor may recognize the symptoms only when you look back.

In babies, trouble communicating includes:

  • Not cuddling

  • Not making eye contact

In younger children, trouble communicating and interacting includes:

  • Being slow to start talking or never learning to talk

  • Avoiding eye contact when talking to someone

  • Repeating words other people have said

  • Talking with a strange rhythm and pitch

  • Not being able to tell from a person's facial expression or body language if the person is happy, angry, or sad

  • Not sharing their thoughts and feelings with others

  • Not interested in having friends

  • Choosing to play alone

Behavior and activity symptoms include:

  • Becoming very upset with any change, such as new food, toys, and clothing

  • Being extremely bothered by certain tastes, smells, or textures

  • Rocking, hand flapping, or spinning

  • Head banging or biting themselves

  • Repeating certain actions, such as watching the same movie over and over or eating the same food at every meal

  • Unusual interests, such as being very interested in vacuum cleaners or ceiling fans

Many people with autism have intellectual disability and learning disorders. Usually, scores are lower on verbal tests than other areas.

How can doctors tell if my child has autism?

Doctors will observe your child in a playroom and ask you and your child’s teachers questions. They'll usually send your child to a psychologist for other tests.

Doctors will also do blood or genetics tests to see if a different problem is causing your child's symptoms, such as a genetic disorder (inherited medical problem).

How is autism treated?

Symptoms are usually lifelong. People with autism with lower intelligence scores are likely to need more support in their adult lives.

Autism is treated with:

  • Behavioral therapy to develop social skills

  • Special education at school

  • Sometimes medicine, such as selective serotonin reuptake inhibitors (SSRIs) or other medicine that may help children stop injuring themselves

Some families try special diets or alternative therapies. There is no good evidence that these are helpful for children with autism. Talk to your doctor about any therapies you're considering.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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