Module 1: What is Autism?


In this module, we will provide a general overview of the characteristics, prevalence, and diagnostic criteria of autism spectrum disorder (ASD).

Module 1 Objectives

  • Describe the characteristics of autism.
  • Explain why autism is a "spectrum" disorder.
  • Describe the prevalence of autism.
  • Describe demographics of autism.
  • List two possible causes of autism.

Module 1 Topics

  • What is autism spectrum disorder (ASD)?
  • How often does autism appear in boys and girls?
  • What might be the cause of autism?

Autism is a complex neurodevelopmental disorder that affects multiple areas of daily life functions.

  • "Neurodevelopmental" means that the causes of autism are rooted in early brain development and functioning.
  • "Daily life functions" include communication, social interactions, behavior, self-care, independent living, education, and employment.


The official term for this condition is "autism spectrum disorder"(ASD), but we also use the more general term "autism." Throughout the modules that you are viewing, we will use these terms interchangeably. You may have heard of other terms associated with autism, such as Asperger syndrome and pervasive developmental disorder not otherwise specified (PDD-NOS). Before 2013, multiple subtypes of ASD were recognized, including Asperger syndrome and PDD-NOS. In 2013, Asperger syndrome and other subtypes were merged into the single category of ASD.

Individuals with ASD have certain common areas of difficulty that affect functioning in varying degrees. To be diagnosed with ASD, an individual must exhibit difficulties in communication, social interactions, and behavior. We will discuss specific characteristics in each of those categories in Modules 3, 4, and 5. Some individuals have severe impairments in those areas which have substantial effects on daily life functioning. Other individuals have only mild impairments. Some people with ASD have IQ scores consistent with severe intellectual disability while others have IQ scores much higher than the average IQ found in people without autism. Some individuals with ASD also have other areas of impairment, including intellectual disabilities, or physical health problems such as seizure disorders and sleep difficulties.

Because ASD symptom severity can range from mild to severe, individuals with ASD are all very different. There is not one profile or set of characteristics that easily applies to all people with autism. Therefore, the term "Autism Spectrum Disorder" is used because the word spectrum highlights the wide range of abilities, challenges, and characteristics of people with ASD.

Some individuals with ASD have unique, advanced skills in particular areas. For example, some are able to do such things as:

  • Listen to something one time (a song, commercial, movie, etc.) and know the lyrics, or every line in the commercial or movie.
  • Compute complicated math problems without pencil, paper, or calculator.
  • Draw, paint, or produce other advanced forms of art.
  • Play a musical instrument, especially a piano, without lessons or learning to read music.
  • Retain trivia and facts about a particular topic. For example, one young man is an expert in flags, and can identify virtually every flag in the world, and state facts about each flag.

For some individuals with ASD, these areas of unusual ability may provide a hobby, or may even lead to a career. Unfortunately, these highly developed skills do not always enable the individual to be successful in school, live more independently, or maintain a job.

How prevalent is autism?

According to the Centers for Disease Control and Prevention, 1 in 68 children have been diagnosed with ASD.

  • ASD occurs more often among boys (1 in 42) than girls (1 in 189).
  • ASD occurs across all demographic groups, including all racial, ethnic, and socioeconomic groups although it is less likely to be diagnosed in some minority groups than other similar developmental disorders.
  • The population of adults with ASD is growing very rapidly and the likelihood of encountering an adult with ASD increases every year.

What causes autism?

There is no clear, single cause of autism. In fact, the answer to that question is probably that there are many contributing factors to ASD, and more than one cause.

Research indicates that changes in certain genes and atypical brain development may contribute to ASD. Certain conditions that occur before and during birth may also increase the risk of ASD. Finding the cause of autism is complicated by the fact that researchers believe that autism appears as a result of a combination of genetic, neurological, and environmental factors. Thus, it appears that there is no single cause of autism.

ASD appears to run in families. Parents who have one child with autism have an increased risk of having a second child with autism. In identical twins, autism may affect each twin.

Although autism probably begins before birth while the brain is developing, symptoms are often first noticed before a child is 3 years old. There is no medical test for autism and no cure. Researchers continue to search for definitive causes and better methods for early detection of autism.

Introduction | Module 2