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What is Autism?


Autism is a spectrum disorder that has no known cause. The symptoms and characteristics of ASD can present themselves in a wide variety of combinations, from mild to severe. Although ASD is defined by a set of certain characteristics, children and adults can exhibit any combination of these characteristic in any degree of severity.  Impaired characteristics include: 

Language and Communication

  • Difficulty in expressing needs (use of gestures or pointing instead of words)

  • Repetition of words or phrases instead of typical, responsive language

  • Literal interpretation of language

  • Difficulty in understanding nonverbal cues, including facial expressions

  • Not responsive to verbal cues (acting as if deaf although hearing tests in normal range)


Social Skills

  • Lack of social interaction

  • Little or no eye contact

  • No sense or feeling of personal distance from others

  • Inappropriate peer interactions

  • Responses that do not match situations (e.g., over- or under-reaction)


Unique Behaviors

  • Insistence on sameness; resistance to change

  • Tantrums/meltdowns

  • Sustained odd play

  • Special interests or inappropriate attachment to objects (e.g., spins or lines up objects)

  • Stereotyped behaviors, including hand flapping, whole-body rocking, clapping, etc.



  • Lack of awareness of own and others’ feelings

  • Little or no display of affection

  • No real fear of danger


Sensory and Motor Skills

  • Over- or under-sensitivity related to one or more sensory processing systems, including touch, balance, body awareness, sight, hearing, taste, smell

  • Clumsy gross-/fine-motor skills

  • Odd posture or gait

  • Noticeable physical over-activity or extreme under-activity


There are no medical tests for diagnosing autism. An accurate diagnosis must be based on observation of the individual’s communication, behavior, and developmental levels. However, because many of the behaviors associated with autism are shared with other disorders, various medical tests may rule out or identify other possible causes of the symptoms being exhibited. 

Research indicates that early diagnosis is associated with dramatically better outcomes for individuals with autism. The earlier a child is diagnosed, the earlier he can begin benefiting from one of many specialized interventions. Be sure to look for possible "red flags" in individuals.


For more information on which "red flags" to look for, please visit The Centers for Disease Control and Prevention (CDC) website


Diagnostic Criteria (DSM-5, 2013)

In May of 2013, the American Psychiatric Association (APA) released a new version of the Diagnostic and Statistical Manual of Mental Disorders, the DSM-5.  This manual is the standard reference that healthcare providers use to diagnose mental and behavioral conditions.  The DSM-5 includes a new diagnosis for autism spectrum disorder (ASD), which replaces the previous diagnoses (autism, PDD-NOS, Asperger Syndrome, Rett’s Disorder, and Childhood Integrative Disorder).


In addition to the new ASD diagnosis, there are two related diagnoses, Social Communication Disorder (SCD) and Disruptive Mood Dysregulation Disorder (DMDD).  For further information about the new diagnoses of ASD, SCD, or DMDD, visit

Diagnostic and Screening Tools

  • Autism Diagnostic Interview - Revised (ADI-R; Rutter, LeCouteur, & Lord, 2003)

  • Autism Diagnostic Observation Schedule - Generic (ADOS-G; Lord, Rutter, DiLavore, & Risi, 2001)

  • Childhood Autism Rating Scale (CARS; Schopler, Reichler, & Renner, 1988)

  • Autism Spectrum Quotient (AQ-Adol; Baron-Cohen, Hoekstra, Knickmeyer, & Wheelwright, 2006; AQ-Child; Auyeung, Baron-Cohen, Wheelwright. & Allison, 2008)

  • Early Screening of Autistic Traits (ESAT; Swinkels et al., 2006)

  • Modified Checklist for Autism in Toddlers (MCHAT; Robbins, Fiein, Barton, & Green, 2001)

  • Screening Tool for Autism in Two-Year-Olds (STAT; Stone, Coonrod, & Ousley, 2000)

Prevalence of ASD

The prevalence of autism spectrum disorder (ASD) is increasing. On March 28, 2014 the CDC released a new report on the prevalence of ASD. The overall prevalence is now one in 68 children (aged 8 years) based upon 2010 data published in 2014. Based upon the current report, the ASD prevalence estimates one in 42 boys and one in 189 girls. ASD knows no racial, ethnic, or social boundaries, and family income, lifestyle, and educational levels do not affect the chance of the occurrence of ASD.



There is currently no cure for ASD. However, research shows that early intervention treatment services can improve a child’s development.2, 3 Early intervention services help children from birth to 3 years old (36 months) learn important skills. Services can include therapy to help the child talk, walk, and interact with others. Therefore, it is important to talk to your child’s doctor as soon as possible if you think your child has ASD or other developmental problem.


Even if your child has not been diagnosed with an ASD, he or she may be eligible for early intervention treatment services. The Individuals with Disabilities Education Act (IDEA) says that children under the age of 3 years (36 months) who are at risk of having developmental delays may be eligible for services. These services are provided through an early intervention system in your state. Through this system, you can ask for an evaluation.


In addition, treatment for particular symptoms, such as speech therapy for language delays, often does not need to wait for a formal ASD diagnosis.

Learn about types of treatments »


Causes and Risk Factors

We do not know all of the causes of ASD. However, we have learned that there are likely many causes for multiple types of ASD. There may be many different factors that make a child more likely to have an ASD, including environmental, biologic and genetic factors.


  • Most scientists agree that genes are one of the risk factors that can make a person more likely to develop ASD.4

  • Children who have a sibling with ASD are at a higher risk of also having ASD. 5-10

  • ASD tends to occur more often in people who have certain genetic or chromosomal conditions, such as fragile X syndrome  or tuberous sclerosis.11-14

  • When taken during pregnancy, the prescription drugs valproic acid and thalidomide have been linked with a higher risk of ASD.15-16

  • There is some evidence that the critical period for developing ASD occurs before, during, and immediately after birth. 17

  • Children born to older parents are at greater risk for having ASD.18


ASD continues to be an important public health concern. Like the many families living with ASD, CDC wants to find out what causes the disorder. Understanding the factors that make a person more likely to develop ASD will help us learn more about the causes. We are currently working on one of the largest U.S. studies to date, called Study to Explore Early Development (SEED). SEED is looking at many possible risk factors for ASD, including genetic, environmental, pregnancy, and behavioral factors.

Learn more about CDC’s research on possible causes and risk factors for ASD »


Who is Affected

ASD occurs in all racial, ethnic, and socioeconomic groups, but is about 4.5 times more common among boys than among girls.


For over a decade, CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network has been estimating the number of children with ASD in the United States. We have learned a lot about how many U. S. children have ASD. It will be important to use the same methods to track how the number of children with ASD is changing over time in order to learn more about the disorder.

Learn more about CDC's tracking of the number of children with ASD »


If You’re Concerned

If you think your child might have ASD or you think there could be a problem with the way your child plays, learns, speaks, or acts, contact your child’s doctor, and share your concerns.

If you or the doctor is still concerned, ask the doctor for a referral to a specialist who can do a more in-depth evaluation of your child. Specialists who can do a more in-depth evaluation and make a diagnosis include:

  • Developmental Pediatricians (doctors who have special training in child development and children with special needs)

  • Child Neurologists (doctors who work on the brain, spine, and nerves)

  • Child Psychologists or Psychiatrists (doctors who know about the human mind)

At the same time, call your state’s public early childhood system to request a free evaluation to find out if your child qualifies for intervention services. This is sometimes called a Child Find evaluation. You do not need to wait for a doctor’s referral or a medical diagnosis to make this call.


Where to call for a free evaluation from the state depends on your child’s age:

  • If your child is not yet 3 years old, contact your local early intervention system.

  • You can find the right contact information for your state by calling the Early Childhood Technical Assistance Center (ECTA) at 919-962-2001.

  • Or visit the ECTA website.

  • If your child is 3 years old or older, contact your local public school system.

  • Even if your child is not yet old enough for kindergarten or enrolled in a public school, call your local elementary school or board of education and ask to speak with someone who can help you have your child evaluated.

  • If you’re not sure who to contact, call the Early Childhood Technical Assistance Center (ECTA) at 919-962-2001.

  • Or visit the ECTA website.


Research shows that early intervention services can greatly improve a child’s development.2, 3 In order to make sure your child reaches his or her full potential, it is very important to get help for an ASD as soon as possible.



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  • Handleman, J.S., Harris, S., eds. Preschool Education Programs for Children with Autism (2nd ed). Austin, TX: Pro-Ed. 2000.

  • National Research Council. Educating Children with Autism. Washington, DC: National Academy Press, 2001.

  • Huquet G, Ey E, Bourgeron T. The genetic landscapes of autism spectrum disorders. Annu Re Genomics Hum Genet. 2013; 14: 191-213.

  • Rosenberg RE, Law JK, Yenokyan G, McGready J, Kaufmann WE, Law PA. Characterisitics and concordance of autism spectrum disorders among 277 twin pairs. Arch Pediatr Adolesc Med. 2009; 163(10): 907-914.

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  • Ronald A, Happe F, Bolton P, Butcher LM, Price TS, Wheelwright S, Baron-Cohen S, Plomin R. Genetic heterogeneity between the three components of the autism spectrum: A twin study. J. Am. Acad. Child Adolesc. Psychiatry. 2006; 45(6): 691-699.

  • Taniai H, Nishiyama T, Miyahci T, Imaeda M, Sumi S. Genetic influences on the board spectrum of autism: Study of proband-ascertained twins. Am J Med Genet B Neuropsychiatr Genet. 2008; 147B(6): 844-849.

  • Ozonoff S, Young GS, Carter A, Messinger D, Yirmiya N, Zwaigenbaum L, Bryson S, Carver LJ, Constantino JN, Dobkins K, Hutman T, Iverson JM, Landa R, Rogers SJ, Sigman M, Stone WL. Recurrence risk for autism spectrum disorders: A Baby Siblings Research Consortium study. Pediatrics. 2011; 128: e488-e495.

  • Sumi S, Taniai H, Miyachi T, Tanemura M. Sibling risk of pervasive developmental disorder estimated by means of an epidemiologic survey in Nagoya, Japan. J Hum Genet. 2006; 51: 518-522.

  • DiGuiseppi C, Hepburn S, Davis JM, Fidler DJ, Hartway S, Lee NR, Miller L, Ruttenber M, Robinson C. Screening for autism spectrum disorders in children with Down syndrome. J Dev Behav Pediatr. 2010; 31: 181-191.

  • Cohen D, Pichard N, Tordjman S, Baumann C, Burglen L, Excoffier E, Lazar G, Mazet P, Pinquier C, Verloes A, Heron D. Specific genetic disorders and autism: Clinical contribution towards their identification. J Autism Dev Disord. 2005; 35(1): 103-116.

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  • Christensen J, Grønborg TK, Sørensen MJ, Schendel D, Parner ET, Pedersen LH, Vestergaard M. Prenatal valproate exposure and risk of autism spectrum disorders and childhood autism. JAMA. 2013; 309(16): 1696-1703.

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