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About Autism

Early identification

The characteristic behaviors of autism spectrum disorder may be apparent in infancy (18 to 24 months), but they usually become clearer during early childhood (24 months to 6 years).

As part of a well-baby or well-child visit, your child's doctor should perform a "developmental screening," asking specific questions your baby's progress. The National Institute of Child Health and Human Development (NICHD) lists five behaviors that warrant further evaluation:

  • Does not babble or coo by 12 months
  • Does not gesture (point, wave, grasp) by 12 months
  • Does not say single words by 16 months
  • Does not say two-word phrases on his or her own by 24 months
  • Has any loss of any language or social skill at any age

Any of these five "red flags" does not mean your child has autism. But because the disorder's symptoms vary so widely, a child showing these behaviors should be evaluated by a multidisciplinary team. This team might include a neurologist, psychologist, developmental pediatrician, speech/language therapist, learning consultant or other professionals who are knowledgeable about autism.

For more information, visit the Infants and Toddlers page or the CDC's "Learn the Signs, Act Early" program.


When parents or support providers become concerned that their child is not following a typical developmental course, they turn to experts, including psychologists, educators and medical professionals, for a diagnosis.

At first glance, some people with autism may appear to have an intellectual disability, sensory processing issues, or problems with hearing or vision. To complicate matters further, these conditions can co-occur with autism. However, it is important to distinguish autism from other conditions, as an accurate and early diagnosis can provide the basis for an appropriate educational and treatment program.

Other medical conditions or syndromes, such as sensory processing disorder, can present symptoms that are confusingly similar to autism's. This is known as differential diagnosis.

There are many differences between a medical diagnosis and an educational determination, or school evaluation, of a disability. A medical is made by a physician based on an assessment of symptoms and diagnostic tests. A medical diagnosis of autism spectrum disorder, for instance, is most frequently made by a physician according to the Diagnostic and Statistical Manual (DSM5, released 2013) of the American Psychological Association. This manual guides physicians in diagnosing autism spectrum disorder according to a specific number of symptoms.

A brief observation in a single setting cannot present a true picture of someone's abilities and behaviors. The person's developmental history and input from parents, caregivers and/or teachers are important components of an accurate diagnosis.

An educational determination is made by a multidisciplinary evaluation team of various school professionals. The evaluation results are reviewed by a team of qualified professionals and the parents to determine whether a student qualifies for special education and related services under the Individuals with Disabilities Education Act (IDEA) (Hawkins, 2009).

School The first step in obtaining special education services is for your child to be evaluated. The evaluation can be done when your child is first suspected of having a disability (preplacement evaluation) or when your child's level of functioning changes in one or more areas (re-evaluation). There are two ways in which a child can be evaluated under the Individuals with Disabilities Education Act:

  • The parent can request an evaluation by calling or writing the director of special education or the principal of the child's school.

    If you call, put your request in writing as well, keeping a copy for yourself. This should be part of your routine communication with anyone concerning your child's education. Follow up on all telephone calls with a letter summarizing the conversation. This way, the other party has the opportunity to make corrections to any misunderstood information, and you have a paper trail in case of a disagreement with the school system.

  • The school system may determine that an evaluation is necessary. If so, they must receive written permission from the parent before conducting the evaluation.

    An evaluation should be conducted by a multidisciplinary team or group, which must include at least one teacher or other specialist with specific knowledge in the area of the suspected disability. IDEA mandates that no single procedure can be used as the sole criterion for determining an appropriate education program. The law also requires that the child be assessed in all areas related to the suspected disability, including but not limited to health, vision, hearing, communication abilities, motor skills, and social and/or emotional status.

    If the parents disagree with the results of the evaluation, they may choose to obtain an independent evaluation at public or private expense. You may request a list of professionals that meet state requirements from your school, or you can choose one on your own. If the professional chosen meets appropriate criteria set up by the state, then the school must consider his/her evaluation in developing an IEP.


The above standards also apply for a child who already receives special education services. A re-evaluation must take place at least every three years. It may, however, be conducted more often if the parent or a teacher makes a written request. An evaluation may also focus on a specific area of concern. A re-evaluation of all areas of suspected need is necessary if parents feel their child is not meeting the short-term objectives of his/her current IEP.

Parents who feel their child's placement should be changed need to have a basis for the request. For example, a child may be exhibiting new problem behaviors. It may be necessary to reassess his/her placement or develop new behavior techniques to address this area. As a first step, an evaluation by a specialist familiar with ASD behaviors could be requested. The IEP can then be changed to reflect the results of the evaluation.

For example, a child may have an annual goal to increase her language production and comprehension skills, but is not meeting the objectives developed in her IEP for this goal. The parent may wish to request a re-evaluation with a speech therapist who is knowledgeable about autism. It may be determined from the results that an increase in the weekly number of hours of therapy is necessary.

A re-evaluation of all areas of suspected need may come prior to the scheduled annual IEP meeting. If the child has made significant progress since the last evaluation, the treatment, placement and therapy recommendations may no longer be applicable. A re-evaluation addressing all areas would become the basis for a more appropriate IEP.

Parents may suggest that professionals with knowledge of autism be present at the school for these evaluations. The school does not have to use the suggested professional, but may appreciate the assistance in finding a qualified person. As explained above, if the parents disagree with the school's evaluation, they do have a right to acquire an independent evaluation.

The evaluation (school or independent) should become the basis for writing the child's IEP. The IEP must be prepared and agreed upon before placement decisions are made, rather than written after the fact to fit the placement decision.

Medical Diagnosis

There are no medical tests for diagnosing autism. An accurate diagnosis must be based on observation of the individual's communication, social interaction, and his or her activities and interests.

Because many of the behaviors associated with autism are common to other disorders, some medical tests can be performed in order to identify other causes or diagnoses. People with autism often have symptoms of various co-occurring mental, behavioral and physical conditions.

Medical professionals who may have experience with autism and other neurodevelopmental disorders include pediatricians (especially developmental pediatricians), neurologists (specifically pediatric neurologists), and child and adolescent psychiatrists. Not every one of these professionals has experience with autism, so parents and caregivers should seek recommendations of knowledgeable professionals in their area from:

  • their local Autism Society affiliate
  • autism support groups
  • people who have children or other family members with autism
  • their primary-care provider

A skilled practitioner can begin the assessment; the evaluation itself can vary depending on the professional administering it, the age of the person being assessed, the severity of his or her symptoms, and local available resources.

For example, if a very young child (1-3 years old) is showing significant developmental delays, a primary-care practitioner may refer the family to a psychologist, pediatric neurologist or developmental pediatrician for a diagnostic assessment. Read this guide from the Autism Advocate to learn more.

An initial medical assessment typically includes:

  • a medical history of the mother's pregnancy
  • developmental milestones
  • eating and sleeping habits
  • coordination
  • stomach and bowel functioning
  • sensory challenges
  • allergies
  • medical illnesses, including ear infections and seizures
  • any family history of developmental disorders
  • any family history of genetic and metabolic disorders
  • parents' and the child's exposure to environmental toxins
  • a thorough physical exam
  • routine lab tests

While there is no one behavioral or communications test that can detect autism, several screening instruments are now being used in diagnosing it.

Related Conditions

Low IQ: Research studies have frequently used inappropriate IQ tests, such as verbal tests with nonverbal children, and in some cases have estimated children's intelligence level without any objective evidence. Tests that do not require language skills, such as the Test of Nonverbal Intelligence (TONI), can offer more accurate information about the person.

Seizures: It is estimated that around 30 percent of people with autism develop epilepsy, some in early childhood and others as they go through hormone level changes in puberty. Suspected seizures should be confirmed by electroencephalogram (EEG) and treated with prescribed anticonvulsant medications.

Chronic Constipation and/or Diarrhea: Medical literature states that about 45 percent of children with autism and 47 percent of adults on the spectrum have gastrointestinal symptoms. Diarrhea is most common, abdominal pain is cited next most frequently, and constipation is reported slightly less. Constipation in autism is usually not hard, impacted stools, but the slow passage of stools with long gaps in between, and loose stools when they do come.

Sleep Problems: Many individuals with autism have sleep problems. Night waking may be due to gastrointestinal issues, allergies, environmental intolerances, seizures or the effects of medications. Other potential causes are sleep apnea (pauses in breathing when the airway becomes obstructed during sleep), sleep terrors or confusional arousals. Children with sensory processing difficulties may have more problems falling asleep and increased periods of night waking. The Autism Society offers a guide on sleep problems and strategies for solving them.

Pica: About 30 percent of children with autism have moderate to severe pica, which means they eat non-food items such as paint, sand, dirt, paper, etc. Pica can be dangerous as ingesting these inedible substances can cause choking, digestive problems, parasitic infections and other illnesses.

Low Muscle Tone: About 30 percent of children with autism have moderate to severe loss of muscle tone, which can limit their gross and fine motor skills.

Sensory Processing Disorder: Many people with autism have sensory processing
disorder (formerly known as sensory integration disorder), which involves unusual sensitivities to sounds, sights, touch, taste and smells. High-pitched intermittent sounds, such as fire alarms or school bells, may be painful to these children. Scratchy fabrics and clothing tags may also be intolerable, and some children have visual sensitivities, such as to the flickering of fluorescent lights.

Allergies/ Immune System: Many children with autism also suffer immune system deficiencies or immune dysregulation. Within the autism spectrum population, there are groups that will experience rashes, allergic sensitivities, gastrointestinal, ear and other infections as a result. Immune deficiencies and/or immune dysregulation make a person with autism more vulnerable to infection, chronic inflammation and autoimmune reactions, most frequently in the brain and gastrointestinal tract (Jepson, 2007).

Pain: Some people with autism have very high pain thresholds (insensitivity to pain), while others have very low pain thresholds. There are interventions, such as sensory integration therapy, designed to help normalize their senses.

Hearing and Visual Impairments

Children with a dual diagnosis of autism and a sensory impairment face many possible paths. If the child is born deaf/hard of hearing or blind/visually impaired, that diagnosis is usually made early on, and autism behaviors may be mistaken for a reaction to the sensory loss. Conversely, if a child with autism has progressive hearing and visual impairments, his or her adaptation to the sensory loss may be misunderstood as a behavior of autism. For more information, visit the Nebraska Center for the Education of Children who are blind or Visually Impaired or this article about autism and deafness.

About 30 percent of children receiving education related to deafness/hard of hearing and blindness/visual impairment are also identified as having autism. Every child should be able to enter his/her education program in the best aural and visual health possible, and should be monitored and tested to ensure continued health and care. For more in-depth information on hearing and vision screenings for people with autism, see this article from the Autism Advocate.

Families can feel overwhelmed and isolated while searching for information. An Autism Society subgroup, the Autism Network For Individuals Deaf/Hard Of Hearing and Blind/Visually Impaired, holds its annual meeting at the Autism Society's National Conference every July. The network, which has worldwide family and professional membership, provides links to other families and researchers through the Autism Research Institute.

Diagnostic Classifications

The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, most recently released as the DSM-5 in 2013, is used by many organizations, individuals and government to diagnosis psychiatric disorders such as autism.

The DSM-5 redefined autism. Its predecessor, the DSM-IV-TR, included five Pervasive Developmental Disorders (PDDs): Autistic Disorder, Asperger's Disorder, Rett's Disorder, Childhood Disintegrative Disorder and Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS).

In the DSM-5, Autistic Disorder, Asperger's Disorder and PDD-NOS are replaced by the diagnosis of Autism Spectrum Disorder. Additionally, the DSM-5 also reduces social-related elements of autism into social communication impairment and repetitive/restricted behaviors, though the labels of Asperger's and PDD-NOS are still in common use.

Those who worked on the DSM-5 repeated many times that no one who already had a diagnosis of autism will be impacted by these changes. However, it is possible that the government and other program providers might choose to re-diagnose their beneficiaries under the new definition to determine whether they are still considered to be living with autism for purposes of receiving services.

We applaud the National Institute of Mental Health and its director Dr. Tom Insel, who has chosen not to place so much weight on the DSM-5 diagnosis categories. NIMH will not use DSM categories as the "gold standard" and will begin moving away from an exclusive focus on symptom-based categories.

The Autism Society strongly urges every government unit and service provider not to reduce or eliminate services to people who were already getting services. In addition, we encourage them to fully understand and appreciate that a person who might not be defined as living with autism under the new DSM-5 criteria might still need a helping hand.

Screening Instruments

Early identification is associated with dramatically better outcomes for people with autism. The earlier a child is diagnosed, the earlier he or she can begin benefiting from early intervention treatment and education.

The Centers for Disease Control and Prevention's National Center on Birth Defects and Developmental Disabilities (NCBDD) recommends that all children be screened for autism by their family pediatrician three times by the age of three – at nine, 18, and 24 or 30 months. Treatment should start when an autism diagnosis is suspected, rather than when a formal diagnosis is made.

The advantages of early intervention cannot be overemphasized. Children who receive intensive therapy can make tremendous strides in their overall functioning.

The NCBDDD provides a wealth of information on the early signs of autism through its "Learn the Signs. Act Early" initiative.

While there is no one behavioral or communications test that can detect autism, several screening instruments have been developed for use in diagnosing it. For detailed information about these instruments and the research behind them, see guide from the Texas Statewide Leadership for Autism Training.


There is no known single cause for autism spectrum disorder, but it is generally accepted that it is caused by abnormalities in brain structure or function. Brain scans show differences in the shape and structure of the brain in children with autism compared to in neurotypical children. Researchers are investigating a number of theories, including the links among heredity, genetics and medical problems.

In many families, there appears to be a pattern of autism or related disabilities, further supporting the theory that the disorder has a genetic basis. While no one gene has been identified as causing autism, researchers are searching for irregular segments of genetic code that children with autism may have inherited. It also appears that some children are born with a susceptibility to autism, but researchers have not yet identified a single "trigger" that causes autism to develop.

Other researchers are investigating the possibility that under certain conditions, a cluster of unstable genes may interfere with brain development, resulting in autism. Still other researchers are investigating problems during pregnancy or delivery as well as environmental factors such as viral infections, metabolic imbalances and exposure to chemicals.

Genetic Vulnerability

Autism tends to occur more frequently than expected among individuals who have certain medical conditions, including fragile X syndrome, tuberous sclerosis, congenital rubella syndrome and untreated phenylketonuria (PKU). Some harmful substances ingested during pregnancy also have been associated with an increased risk of autism.

Environmental Factors

Research indicates other factors besides the genetic component are contributing to the rise in increasing occurrence of autism – for example, environmental toxins (e.g., heavy metals such as mercury), which are more prevalent than in the past. Those with autism (or those at risk) may be especially vulnerable to such toxins, as their ability to metabolize and detoxify these exposures might be compromised.

Asperger's Syndrome

Simple Diagnosis
Early Identification Diagnosis Re-evaluation Medical Diagnosis Related Conditions


Asperger's syndrome (also known as Asperger's Disorder) was first described in the 1940s by Viennese pediatrician Hans Asperger, who observed autism-like behaviors and difficulties with social and communication skills in boys who had normal intelligence and language development. Many professionals felt Asperger's syndrome was simply a milder form of autism and used the term "high functioning autism" to describe these individuals. Uta Frith, a professor at the Institute of Cognitive Neuroscience of University College London and editor of Autism and Asperger Syndrome, describes individuals with Asperger's as "having a dash of autism." Asperger's Disorder was added to the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) in 1994 as a separate disorder from autism. However, there are still many professionals who consider Asperger's Disorder a less severe form of autism. In 2013, the DSM-5 replaced Autistic Disorder, Asperger's Disorder and other pervasive developmental disorders with the umbrella diagnosis of autism spectrum disorder.


What distinguishes Asperger's Disorder from classic autism are its less severe symptoms and the absence of language delays. Children with Asperger's Disorder may be only mildly affected, and they frequently have good language and cognitive skills. To the untrained observer, a child with Asperger's Disorder may just seem like a neurotypical child behaving differently.

Children with autism are frequently viewed as aloof and uninterested in others. This is not the case with Asperger's Disorder. Individuals with Asperger's Disorder usually want to fit in and have interaction with others, but often they don't know how to do it. They may be socially awkward, not understand conventional social rules or show a lack of empathy. They may have limited eye contact, seem unengaged in a conversation and not understand the use of gestures or sarcasm.

Their interests in a particular subject may border on the obsessive. Children with Asperger's Disorder often like to collect categories of things, such as rocks or bottle caps. They may be proficient in knowledge categories of information, such as baseball statistics or Latin names of flowers. They may have good rote memory skills but struggle with abstract concepts.

One of the major differences between Asperger's Disorder and autism is that, by definition, there is no speech delay in Asperger's. In fact, children with Asperger's Disorder frequently have good language skills; they simply use language in different ways. Speech patterns may be unusual, lack inflection or have a rhythmic nature, or may be formal, but too loud or high-pitched. Children with Asperger's Disorder may not understand the subtleties of language, such as irony and humor, or they may not understand the give-and-take nature of a conversation.

Another distinction between Asperger's Disorder and autism concerns cognitive ability. While some individuals with autism have intellectual disabilities, by definition, a person with Asperger's Disorder cannot have a "clinically significant" cognitive delay, and most possess average to above-average intelligence.

While motor difficulties are not a specific criterion for Asperger's, children with Asperger's Disorder frequently have motor skill delays and may appear clumsy or awkward.


Diagnosis of Asperger's Disorder has increased in recent years, although it is unclear whether it is more prevalent or more professionals are detecting it. When Asperger's and autism were considered separate disorders under the DSM-IV, the symptoms for Asperger's Disorder were the same as those listed for autism; however, children with Asperger's do not have delays in the area of communication and language. In fact, to be diagnosed with Asperger's, a child must have normal language development as well as normal intelligence. The DSM-IV criteria for Asperger's specified that the individual must have "severe and sustained impairment in social interaction, and the development of restricted, repetitive patterns of behavior, interests and activities that must cause clinically significant impairment in social, occupational or other important areas of functioning."

The first step to diagnosis is an assessment, including a developmental history and observation. This should be done by medical professionals experienced with autism and other PDDs. Early diagnosis is also important as children with Asperger's Disorder who are diagnosed and treated early in life have an increased chance of being successful in school and eventually living independently.

Early Identification

The characteristic behaviors of autism spectrum disorder may be apparent in infancy (18 to 24 months), but they usually become clearer during early childhood (24 months to 6 years).

As part of a well-baby or well-child visit, your child's doctor should perform a "developmental screening," asking specific questions your baby's progress. The National Institute of Child Health and Human Development (NICHD) lists five behaviors that warrant further evaluation:

  • Does not babble or coo by 12 months
  • Does not gesture (point, wave, grasp) by 12 months
  • Does not say single words by 16 months
  • Does not say two-word phrases on his or her own by 24 months
  • Has any loss of any language or social skill at any age

Any of these five "red flags" does not mean your child has autism. But because the disorder's symptoms vary so widely, a child showing these behaviors should be evaluated by a multidisciplinary team. This team might include a neurologist, psychologist, developmental pediatrician, speech/language therapist, learning consultant or other professionals who are knowledgeable about autism.

For more information, visit the Infants and Toddlers page or the CDC's "Learn the Signs, Act Early" program.

Facts and Statistics

About 1 percent of the world population has autism spectrum disorder. (CDC, 2014)

Prevalence in the United States is estimated at 1 in 68 births. (CDC, 2014)

More than 3.5 million Americans live with an autism spectrum disorder. (Buescher et al., 2014)

Prevalence of autism in U.S. children increased by 119.4 percent from 2000 (1 in 150) to 2010 (1 in 68). (CDC, 2014) Autism is the fastest-growing developmental disability. (CDC, 2008)

Prevalence has increased by 6-15 percent each year from 2002 to 2010. (Based on biennial numbers from the CDC)

Autism services cost U.S. citizens $236-262 billion annually. (Buescher et al., 2014)

A majority of costs in the U.S. are in adult services – $175-196 billion, compared to $61-66 billion for children. (Buescher et al., 2014)

In 10 years, the annual cost will be $200-400 billion. (Autism Society estimate)

Cost of lifelong care can be reduced by 2/3 with early diagnosis and intervention. (Autism Society estimate based on Government Accounting Office Report on Autism, 2007)

1 percent of the adult population of the United Kingdom has autism spectrum disorder. (Brugha T.S. et al., 2011)

The U.S. cost of autism over the lifespan is about $2.4 million for a person with an intellectual disability, or $1.4 million for a person without intellectual disability. (Buescher et al., 2014)

35 percent of young adults (ages 19-23) with autism have not had a job or received postgraduate education after leaving high school. (Shattuck et al., 2012)

It costs more than $8,600 extra per year to educate a student with autism. (Lavelle et al., 2014) (The average cost of educating a student is about $12,000 – NCES, 2014)

In June 2014, only 19.3 percent of people with disabilities in the U.S. were participating in the labor force – working or seeking work. Of those, 12.9 percent were unemployed, meaning only 16.8 percent of the population with disabilities was employed. (By contrast, 69.3 percent of people without disabilities were in the labor force, and 65 percent of the population without disabilities was employed.) (Bureau of Labor Statistics, 2014)

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