Autism spectrum disorder (ASD) is a developmental disorder that affects a person’s ability to socialize and communicate with others. ASD can also result in restricted, repetitive patterns of behavior, interests or activities. The term “spectrum” refers to the wide range of symptoms, skills and levels of impairment or disability that people with ASD can display. Some people are mildly impaired by their symptoms, while others are severely disabled.

The prevalence rate for ASD is 1 in 68 children and rising. Boys are 4 times more likely than girls to develop autism. ASD crosses racial, ethnic and social backgrounds equally. Awareness of this disorder and improved screening methods have contributed to the increase in diagnoses in recent years.


Symptoms of autism start to appear during the first three years of life. Typically, developing infants are social by nature. They gaze at faces, turn toward voices, grasp a finger and even smile by 2-3 months of age. By contrast, most children who develop autism have difficulty engaging in the give-and-take of everyday human interactions.

Not everyone will experience symptoms with the same severity, but all people with ASD will have symptoms that affect social interactions and relationships, verbal and nonverbal communication and preoccupation with certain activities. Along with different interests, autistic children generally have different ways of interacting with others. Often, parents are the first to notice that their child is showing unusual behaviors, such as failing to make eye contact, not responding to his or her name or playing with toys in unusual, repetitive ways.

Symptoms of autism can include:

  • Delay in language development, such as not responding to their own name or speaking only in single words, if at all.
  • Repetitive and routine behaviors, such as walking in a specific pattern or insisting on eating the same meal every day.
  • Difficulty making eye contact, such as focusing on a person’s mouth when that person is speaking instead of their eyes, as is usual in most young children.
  • Sensory problems, such as experiencing pain from certain sounds, like a ringing telephone or not reacting to intense cold or pain, certain sights, sounds, smells, textures and tastes.
  • Difficulty interpreting facial expressions, such as misreading or not noticing subtle facial cues, like a smile, wink or grimace, that could help understand the nuances of social communication.
  • Problems with expressing emotions, such as facial expressions, movements, tone of voice and gestures that are often vague or do not match what is said or felt.
  • Fixation on parts of objects, such as focusing on a rotating wheel instead of playing with peers.
  • Absence of pretend play, such as taking a long time to line up toys in a certain way, rather than playing with them.
  • Difficulty interacting with peers, because they have a difficult time understanding that others have different information, feelings and goals.
  • Self-harm behavior, such as hitting his head against a wall as a way of expressing disapproval.
  • Sleep problems, such as falling asleep or staying asleep.

Symptoms of autism fall on a continuum. This means that the learning, thinking and problem-solving abilities of children with ASD can range from gifted to severely challenged. Some children with ASD need a lot of help in their daily lives. With a thorough evaluation, doctors can make a diagnosis to help find the best treatment plan for the child.


Scientists have not discovered a single cause of autism. They believe several factors may contribute to this developmental disorder.

  • Genetics. If 1 child in a family has ASD, another sibling is more likely to develop it too. Likewise, identical twins are highly likely to both develop autism if it is present. Relatives of children with autism show minor signs of communication difficulties. Scans reveal that people on the autism spectrum have certain abnormalities of the brain's structure and chemical function.
  • Environment. Scientists are currently researching multiple environmental factors that are thought to play a role in contributing to ASD. Many prenatal factors may contribute to a child’s development, such as a mother’s health. Other postnatal factors may affect development as well. Despite many claims that have been highlighted by the media, strong evidence has been shown that vaccines do not cause autism.


There is no medical test that can determine the possibility of developing autism, since the genes for ASD have not yet been identified. Specialists make the diagnosis after screening for social deficits, communication problems, and repetitive or restricted behavior.

Diagnosing autism is often a 2-stage process. The first stage involves general developmental screening during well-child checkups with a pediatrician. Children who show some developmental problems are referred for additional evaluation. The second stage involves a thorough evaluation by a team of doctors and other health professionals with a wide range of specialties. At this stage, a child may be diagnosed as having autism or another developmental disorder. Typically, children with ASD can be reliably diagnosed by age 2, though some may not be diagnosed until they are older.

Types of ASD Screening Instruments

Sometimes the doctor will ask parents questions about the child's symptoms to screen for autism. Other screening instruments combine information from parents with the doctor's own observations of the child. Examples of screening instruments for toddlers and preschoolers include:

  • Modified Checklist for Autism in Toddlers (M-CHAT) is a list of informative questions about a child where the answers can indicate whether he or she should be further evaluated by a specialist.
  • Screening Tool for Autism in Two-Year-Olds (STAT) is a set of tasks that children perform under supervision to assess key social and communicative behaviors, including imitation, play and directing attention.
  • Social Communication Questionnaire (SCQ) is a series of questions parents answer to help specialists determine if further testing is needed for a child aged 4 years or older.
  • Communication and Symbolic Behavior Scales (CSBS) uses parent interviews and direct observations of natural play to collect information on communication development, including gestures, facial expressions and play behaviors.

For more information on these screening tools, please visit the Centers for Disease Control and Prevention.


Autism is treated and managed in several ways:

  • Education and development, including specialized classes and skills training, time with therapists and other specialists
  • Behavioral treatments, such as applied behavior analysis (ABA)
  • Medication for co-occurring symptoms, combined with therapy
  • Complementary and alternative medicine (CAM), such as supplements and changes in diet

Though autism cannot be cured, it can be treated effectively.

Related Conditions

A child with autism may have additional disorders. Some of those disorders are:

  • Intellectual disability. Many children with ASD have some degree of intellectual disability. When tested, some areas of ability may be normal, while others—especially cognitive (thinking) and language abilities—may be relatively weak.
  • Seizures. 1 in 4 children with autism has seizures, often starting either in early childhood or during the teen years. Seizures, caused by electrical activity in the brain, can result in a short-term loss of consciousness, convulsions and staring spells. An electroencephalogram (EEG), a nonsurgical test that records electrical activity in the brain, can help confirm whether a child is having seizures.
  • Fragile X syndrome. Fragile X syndrome is a genetic disorder and is the most common form of inherited intellectual disability, causing symptoms similar to ASD. Around 1 in 3 children who have Fragile X syndrome also meet the diagnostic criteria for autism, and about 1 in 25 children diagnosed with ASD have the mutation that causes Fragile X syndrome. Because this disorder is inherited, children with autism should be checked for Fragile X, especially if the parents want to have more children. For more information on Fragile X, see the Eunice Kennedy Shriver National Institute of Child Health and Human Development website.
  • Tuberous sclerosis. Tuberous sclerosis is a rare genetic disorder that causes noncancerous tumors to grow in the brain and other vital organs. Tuberous sclerosis occurs in 1-4% of people with ASD. A genetic mutation causes the disorder, which has also been linked to intellectual disability, epilepsy and many other physical and mental health problems. There is no cure for tuberous sclerosis, but many symptoms can be treated.
  • Gastrointestinal problems. Some parents of children with autism report that their child has frequent gastrointestinal (GI) or digestion problems, including stomach pain, diarrhea, constipation, acid reflux, vomiting or bloating. If a child has GI problems, a gastroenterologist can help find the cause and suggest appropriate treatment.
  • Co-occurring mental illnesses. Children with autism can also develop mental disorders such as anxiety disorders, attention deficit hyperactivity disorder (ADHD) or depression. Research shows that children with ASD are at higher risk for some mental disorders than children without autism. Managing these co-occurring conditions with medications or behavioral therapy, which teaches children how to control their behavior, can reduce symptoms that appear to worsen a child's  symptoms.
  • Rett syndrome. Rett syndrome is a developmental disorder that includes a regression in development. Unlike autism, Rett syndrome mostly affects girls. 1 of every 10,000-22,000 girls has Rett syndrome. Children with Rett syndrome develop normally for 6-18 months before regression and autism-like symptoms appear. However, after this period, most children with Rett syndrome improve their social communication skills, and autistic features are no longer a major area of concern.