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Autism facts for kids

Kids Encyclopedia Facts
Autism-stacking-cans 2nd edit
A boy with autism stacks up cans over and over again.

Autism, also called Autism Spectrum Disorder (ASD) describes a group of complex disorders of brain development such as Asperger’s Syndrome, Atypical Autism and Childhood Autism. ASD is a lifelong developmental condition that affects the way an individual relates to his or her environment and their interaction with other people. The word “spectrum” describes the range of difficulties that autistic people may experience and the degree to which they may be affected. The main areas of difficulty are in social interaction, verbal and nonverbal communication and restricted or repetitive behaviours and interests.

People who have autism find it difficult to act in a way that other people think is "normal". They find it difficult to talk to other people and to look at other people. Often, they do not like being touched by other people. A person who has autism seems to be turned inwards. They may talk only to themselves, rock themselves backwards and forwards, and laugh at their own thoughts. They do not like any type of change and may find it very difficult to learn a new behaviour like using a toilet or going to school.

Autism is caused by the way that the brain develops, both before and after a baby is born. Around the world, about one in every 160 children has an Autism Spectrum Disorder.


Early history

The word “autism” comes from the Greek word “autos”, meaning “self.” The term describes conditions in which a person is removed from social interaction—hence, an “isolated self”. The term "autism" was first used by a psychiatrist named Eugen Bleuler in 1911 to refer to one group of symptoms of schizophrenia. Sigmund Freud adopted the broad concept of Bleuler and equated the term autism with narcissism.


Three decades later, researchers in the United States began to use the term autism to describe children with emotional or social problems. Two researchers by the name of Hans Asperger and Leo Kanner were the pioneers of the research study for autism in the 1940s.

In 1943 Leo Kanner (a doctor from Johns Hopkins University) did a study of 11 children. The children were very intelligent. But he found out that they had difficulties like changing environments, being sensitive to certain stimuli, having speech problems and allergies to food. Later he named the children’s condition “early infantile autism”. Leo Kanner's discovery is now called autistic disorder, childhood autism, infantile autism, or simply autism.

In 1944 Hans Asperger studied separately a group of children and found very similar conditions. But the children in Hans Asperger's group did not repeat words. Also, they had no speech problems like Kanner's did. However, the children did have problems with fine motor skills such as holding a pencil. The children he studied seemed to be clumsier than other children. They also had “[...] a lack of empathy, little ability to form friendships, one-sided conversation, intense absorption in a special interest and clumsy movements”. Hans Asperger described a "milder" form of autism, his discovery is now called Asperger syndrome.

Later history

Schizophrenia and autism were linked in many researchers’ studies. Only since the 1960s, medical professionals began to have a separate understanding of these two disorders. Since 1980, Kanner’s so called early infantile autism is listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM). Precisely because of the vague distinction between schizophrenia and autism, the DSM came out with a more accurate definition of autism in 1987. Henceforth, early infantile autism is called autism disorder. Furthermore, for the first time the DSM introduced standardised criteria to diagnose autism. The fourth edition of the Diagnostic and Statistical Manual of Mental Disorders expanded the definition of autism and included milder cases of autism. But especially the Asperger’s syndrome was added in 1994. With the release of the fifth edition of the DSM in 2013 the subtypes of autism are summarized into the general term Autism Spectrum Disorder (ASD). Individuals are now diagnosed on an autism spectrum with varying levels of intensity (mild, moderate and severe).



A baby without autism will usually be interested in other people. Autistic babies may like objects more than faces and other people. They may look for a second at a face, but quickly turn. They may not smile or may just smile at what they are interested in. Autistic children may usually like to be by themselves. They may not be interested in making friends. They may also not react normally to hugging and other signs of love by their parents. This does not mean that they do not love their parents, they just do not know how to say it. Often, it is difficult for them to know what other people think or feel. For example, they might not see much difference between whether a parent is smiling or feeling sad. They may laugh and cry at the wrong times. Some do not understand that someone else can have different thoughts and feelings than they do. This is a sign of a missing Theory of Mind.


An autistic child might not try to talk, point, or otherwise try to get a message across by one year of age. Some do not understand language at all. Those who speak usually do not show changes in pitch and tone. The voice sounds monotonic. But pitch and tone are important for communication. It helps to interpret the meaning of the words. Often, the use of homographs is difficult for people diagnosed with autism. Many autistic people have problems to understand gestures or facial expression. They seem to have only a limited amount of facial expressions. This makes it difficult to express themselves or understand the expressions of others. However, they may try to communicate using pictures in books, photos, signing or picture cards when they do not speak but have clear understanding of language.

Restricted behaviour

Some autistic people spend a lot of time doing the same thing over and over again like spinning in circles or putting things in order. Other typical behaviours are rocking, twisting and flapping. These behaviours do not serve as communication. They often last up to adulthood and may turn into obsessions or motor tics. Some autistic people may also be interested in unusual things, and may spend all of their time learning about their interests. Many autistic people do not want any change. They will do exactly the same things every day and may even get upset if anything changes. But some can tolerate a change in routine with forwarning.


When comparing autistic and non-autistic children, the autistic children show a greater sensitivity in all senses. This sensitivity may increase over age. But possibly autistic people are only better able to express sensory disturbances with age.

Many autistic children like junk food such as chips, crisps and lemonade but avoid vegetables. Often they do not like soft, mushy or lumpy food. Many do not want to try new foods. Many autistic children also try to eat metal, plastic, paper and stones. Sometimes autistic children do not seem to notice strong smells like foul scents. Numerous autistic children do not like to touch wet or sticky substances. Often they do not like to be touched by other people. The response is a distressed reaction like crying. Many autistic children do not show any sign of pain after a bee sting, a burn or a hard fall.

When it comes to sound, autistic children are attracted to specific sounds from aeroplanes, the ticking of clocks and other mechanical sounds. Often autistic children notice sounds earlier than others do. But many appear to be deaf when it comes to the human voice. Background noises like music, conversations or the wind can be very distracting for them. Many autistic children make unusual sounds that seem to be comforting for them. It is often noticed that their loudness of speech is too soft, too loud or changing continuously between these two levels. This may show a changing comfortable listening level.

A lot of autistic children pay attention to detail. They can look at pictures or books for a very long time. Some are frequently found to gaze into space.

A few autistic children show very good balance skills. Some do not show any dizziness after spinning around for a long time.


Different studies resulted in different numbers of the frequency of autism spectrum disorders. One study stated ten cases of classical autism, 2.5 cases of Asperger's syndrome and 15 cases of mild autism (PDD-NOS) in 10,000 people - tendency: increasing. Other sources speak about 60 autism spectrum disorder cases in 10,000 people. However, the number of autism cases is not equal in men and in women. Here, the results of studies vary highly. Researchers in general say that 3-4 men are diagnosed for every woman that is diagnosed. This ratio decreases for severe cases to 1:1. It increases for high-functioning cases and in Asperger's syndrome reaches a ratio of 8:1. Recently, the awareness has increased that this ratio may be so high because studies are simply missing female autistic people. This could be because tests for autism typically focus on male autism traits. Another possible explanation is that autistic females may be better at adapting to social expectations and hiding their social problems. Studies have suggested that the brains of autistic females may rather be like neurotypical men’s (non-autistic men) brains of the same age. These could be reasons why it is not so easy to realise whether a woman is autistic - and therefore, why more men than women are diagnosed.

Types of Autism Spectrum Disorders

Over the past years, individuals have been using the terms "autism" and "autism spectrum disorder" like they mean the same thing. Autism is a spectrum disorder. This means that some people who have autism are only mildly affected. These people may go to regular schools, go to work, and have partners and families. Some people are affected worse than others. These people may be able to take care of most of their own needs at home like dressing and getting food, but not be able to have a regular job or travel alone. A person who has severe autism may need to be cared for all their life. Few people with autism are extraordinarily gifted or talented. These people are said to have savant syndrome. They are often very good at just one thing in particular, like mathematics, playing the piano or remembering football scores.

The overall category of the Autism Spectrum Disorder is called Pervasive Developmental Disorder. The name describes medical conditions with developmental problems in a number of fields. In most cases, when referring to the Autism Spectrum Disorder, we are referring to the most common disorders:

Type of Autism Childhood Autism Atypical Autism Asperger’s Syndrome
ICD-10 F84.0 F84.1 F84.5
Age of onset Delay or abnormal functioning in communication, language, play and cognitive development before the age of three Atypical Autism may differ from Childhood Autism in age of onset. Here, abnormal behaviour is only visible after the age of three.

Additionally, only one or two of the three categories (social interaction, communication and behaviour) are affected

No noticeable delay of communication, language, play or cognitive development during childhood
Interaction Is affected Is affected
Communication Is affected No delay in language
Behaviour Is affected Is affected

The different categories, the so called “International Classification of Diseases” (ICD), are defined by the World Health Organization. As shown in the table, the diseases vary in several points. These are the age of onset, social interaction, communication and behaviour. An individual belongs to a certain category, depending on the areas of impairment. All three may seem similar in symptoms, yet are not the same. Still, people within one group show similar symptoms. The groups can be used to search for an underlying cause of the disease and to provide a better treatment.


Scientists do not know exactly what causes autism. There may be many different causes for the different types of Autism Spectrum Disorder. Scientists do know about some things that make a person more likely to have an Autism Spectrum Disorder.

Genetics and Heritability

The autism spectrum disorders are highly heritable disorders. This means that it is very likely (over 90%) that the child of an autistic person will also be on the autism spectrum. The reason for this are certain genes. These genes are linked to autism and are passed on from a parent to the child. Already Leo Kanner and Hans Asperger noticed that fathers of autistic children often preferred being on their own over being with people. Therefore, Kanner and Asperger suspected a genetic cause. Studies with families with a child on the autism spectrum were done to investigate this theory. They found that sometimes the children’s parents (fathers as well as mothers) also show social difficulties, shyness and problems with understanding contextual information when talking to someone. Some studies have found this in only 10 out of 100 families, some in as much as 45 out of every 100 families.

Moreover, twin studies showed that it is much more likely that identical twins are both on the autism spectrum than that non-identical twins are both on the autism spectrum. Identical twins have nearly the same DNA. Therefore, it is highly probable that they are either both autistic or both not autistic. Non-identical twins share only half of their genes which makes it less likely that they both have the disorder. Scientists have shown that the recurrence risk (the likelihood that a child is on the autism spectrum if it has a sister or a brother that is autistic as well) is 20 to 80 times higher than the probability for having the disorder in the average population.

However, it is not a single gene that increases the risk for autism spectrum disorders. Several genes have been linked to the disorder. All of the identified genes can in sum only explain one or two out of every ten autism cases. None of the genes that have been found to play a role in autism can explain more than one out of every 100 cases.

The genetic influences include:

  • mutations,
  • genetic syndromes (e.g. Fragile X syndrome),
  • de novo (newly occurring in a family) as well as inherited copy number variations (CNV) - a CNV is the duplication or deletion of a gene - and
  • single nucleotide variants (SNV) - an SNV is a change in one nucleotide that occurs with very low frequency.

The affected genes influence:

  • the interaction between brain cells and synaptic functioning,
  • neuronal growth and neuronal migration (the wandering of a neuron from its birthplace to its final location in the brain) and
  • inhibitory and excitatory neurotransmission.

Neural Correlates

Researchers have not found a single neuronal correlate for autism spectrum disorders, i.e. no abnormal functioning of the brain is the only cause of autism. Nevertheless, scientists found some differences between the brains of autistic people and the typical human brain. These differences lie in the anatomy of the brain, the activity in certain brain regions as well as in the connections between brain regions. It is a general tendency that autistic people use the same brain regions as other people but show different activity. In some areas the activity is less, in others it is stronger. However, this may only be true for male autists. Throughout the last years, studies have shown that brains of autistic women might be like normal men's brains.

Some researchers grouped autistic people's difficulties into three main areas in order to investigate their neuronal basis.

Theory of Mind

Researchers say that building a Theory of mind is one of the main problems for autistic people. This makes it difficult for them to interact with others. Problems in social interaction are probably worsened by low preference for social stimuli, such as faces. This tendency has been found in studies tracking the person’s eye movements and in EEG studies. EEG studies showed lower than normal activity in the fusiform face area (FFA), a brain region that is usually active when seeing faces. However, the results of other studies could not show this.

Also, scientists measured brain activity of people on the autism spectrum with fMRI while they were thinking about their own emotions. They found activity in the same brain regions as in non-autistic people. The difference was that some regions which are important for thinking about oneself and emotions (especially the anterior insula) were less active in autistic people. Other brain regions were much more active. These findings may explain the difficulties people with autism experience when trying to understand complex facial expressions and emotions (such as shame, jealousy).

Executive Function

People on the autism spectrum show a lower ability for executive function. Executive function means physical, emotional and cognitive self-control. This includes planning actions, focusing, shifting attention and flexibility of behaviour and thinking. Autistic people's ability can improve but it will remain below non-autistic people's ability in executive function.

Problems with executive function are probably caused by large networks in the brain. Grey matter and white matter irregularities have a negative influence on the way different brain regions work together (functional integration). A smaller corpus callosum leads to abnormalities in working memory (an active process of keeping a memory until it is needed)  and planning actions.

Central Coherence

Central coherence is the ability to build wholes out of parts. It is weak in people with autism. This means that autistic people focus more on details. They cannot build wholes out of them. Not being able to pay attention to wholes results in difficulties with perception and language. Therefore, people with autism usually need more time for dealing with information coming from their surroundings. As a consequence, they typically also need more time for responding. However, performance varies between people on the autism spectrum. Moreover, the term central coherence may include many interacting aspects. This makes it difficult to find the cause for it in the brain. Neural correlates for central coherence are not yet known.


Diagnosing autism is difficult, since there is no medical test like a blood test. Instead, a diagnostic evaluation involves a team of doctors and other health professionals such as pediatricians, psychologists, speech and language pathologists, who are experienced in diagnosing ASD and know the individual.

Diagnosis in children

A reliable diagnosis can usually be made by the age of two. At the age of 18- and 24-month every child should visit a pediatrician and receive well-child check-ups. If the screening shows abnormalities, an additional evaluation is needed. In this evaluation a team of professionals will interview parents or carers about the child’s behaviour and observe the individual in multiple settings. Behavioural assessments, physical assessments and laboratory tests such as clinical observations, developmental and intelligence tests will be done too. Reviewing a detailed developmental history of the child is also essential in order to receive a diagnosis.

Diagnosis in adults

Autism can also be diagnosed later in life. But it is more difficult because symptoms of autism may overlap with symptoms of other diseases as for instance learning disability or obsessive-compulsive disorder. Psychologists developed behavioural checklists for the purpose of diagnosing children. These checklists do not apply for adults since they often unconsciously learned to hide their symptoms. An expert, most likely a psychologist, does not only ask the adult about concerns, challenges in social interaction and communication or behaviour routines and interest. He also tests the adult in standardised tests. These tests consist of self-assessments in social interaction, communication and relationships. To make a diagnosis information about the developmental history is also required.

Diagnostic and Statistical Manual (DSM-5)

In 2013, the American Psychiatric Association published the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V). In order to be diagnosed with autism, a person must fulfill two standardized criteria. It is important that individuals must show symptoms from early childhood, even if those symptoms are recognized later. These symptoms have to limit everyday functioning. Additionally, these symptoms cannot be explained by an intellectual disability or a developmental delay.

Autism Spectrum Disorder is characterized by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviours.

Diagnostic Criteria 

Long lasting deficits in social communication and social interaction in multiple contexts, as explained by the following - currently or by history

  1. Deficits in social-emotional interaction (e.g., responding inappropriately in conversations; reduced sharing of interests, emotions or affect; failure to respond to social interactions)
  2. Deficits in nonverbal communicative behaviours used for social interaction (e.g., difficulties with interpreting both verbal and nonverbal language like gestures, tone of voice, facial expressions; abnormalities in eye contact and body language; deficits in understanding and use of gestures; a total lack of facial expressions and nonverbal communication)
  3. Deficits in developing, maintaining, and understanding relationships (difficulties in making friends, no interests in peers)

Restricted, repetitive patterns of behaviour, interests, or activities, as explained by at least two of the following - currently or by history

  1. Stereotyped or repetitive motor movements, use of objects or speech (e.g., always using the same movements, objects or words)
  2. Insistence on sameness, inflexible adherence to routines or re-occurring patterns of verbal or nonverbal behaviour (e.g., highly sensitive to changes in their environment; extreme distress at small changes; inflexible thinking patterns, overly dependent on routines)
  3. Highly restricted, fixated interests that are abnormal in intensity or focus (e.g., intensely focused on inappropriate items or unusual objects; highly-focused interests)
  4. Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment (e.g., experience over- or under-sensitivity to sounds, touch, tastes, smells, light, colours, temperatures or pain)

Co-occurring conditions

Autism spectrum disorder includes a wide range of symptoms, skills and levels of disability. Some autistic people also have learning disabilities, mental health issues or other conditions. This means that autism can also co-occur with other diseases and symptoms of the following disorders:

In the DSM-V, a diagnosis of autism excludes making a formal diagnosis of other psychiatric disorders. Therefore other mental health conditions may be undiagnosed in an autistic person, because it is impossible to make a comorbid clinical diagnosis.


Since autism is a spectrum, every person with autism is different. Different treatments help different people. There are a few different categories of treatment. The main ones are medication, different therapies and diets. The treatment is fitted depending on what a person with autism needs.

Picture Exchange Communication System (PECS)

The Picture Exchange Communication System (PECS) is designed for autistic people who do not speak. Pictures and symbols are used to communicate. For example, an autistic child wants to have a cup of water. So, it would show its mother a picture of a cup of water. Thereby, the mother knows what the child wants. So to say, the pictures and symbols will replace speech. The aim is a constant use of these symbols and pictures and to increase communication. Usually, this way of communication does not improve the spoken language.


People with autism often have problems with their digestive organs like the stomach or gut. These problems could be inflammations, abdominal pain, gas, diarrhea or bacterial overgrowth. The reasons may be malnutrition, food intolerances or allergies. Specific food products causing these problems are excluded from the diet. In many cases, products containing gluten or casein,  the main protein occurring in dairy products, are excluded. In many cases vitamins, minerals as well as essential fatty acids are additionally provided. A big problem is that many autistic people cannot tell that they have pain. Therefore many problems concerning the digestive organs stay undetected.


Occupational Therapy

Typically, autistic people are either far more or far less sensitive to sensory information. For example a ringing telephone is perceived much louder or only very soft. This can make it very difficult to interpret the sensory information and create a good response to it. Because of that, autistic people often show enormous difficulties to fulfill daily life activities. Occupational therapy helps autistic people to minimize these difficulties. Individual therapy plans are created. The therapist tries to help the autistic person in many different aspects.

One aspect is the sensory integration. Here the therapist helps the autistic person to make sense of the different sensory inputs. This part of the therapy is important because sensory information is important for learning, communication and performing movements. An example to make children more aware of the sense of touch can be playing with finger paint or collecting objects from a bag of dried beans. Another important aspect of occupational therapy is the training of daily life activities. Here, the person learns things like getting dressed, eating, personal hygiene, cleaning, shopping or financial management. These activities include several steps. Usually only one step is trained at a time. Then it gets combined with the steps that the person has already learned.

Play therapy is also important - especially for children. It helps to learn about emotions like happiness or anxiety. It also helps to learn certain behaviours. An example would be learning to shake hands with unknown people instead of hugging them. The play therapy can also help to solve problems, learn basic forms of communication and improve creativity.

Free time between therapeutic activities is important as well. Here, the person can do whatever he or she likes. For example, playing with toys, sleeping or doing a physical activity like running, swimming or climbing. Sports can also help to reduce repetitive movements, improve movement coordination and is a possibility to interacting with other people.

Therapy with Animals

Often animals are used to help autistic people. Most often dogs or horses are used. The people diagnosed with autism can care for these animals, pet them and in the case of the horse even ride on them. Studies showed that the interaction between an autistic person and animals can increase communication, reduce stress, fear, aggression and reduce the severity of the symptoms of autism.

Music Therapy

Music therapy consists of two parts: One is an active listening part. Here, the therapist is making music himself or playing music from a record. In the other part, the autistic person can make music himself like playing an instrument or singing. Music therapy will improve different aspects of communication.

Art Therapy

Here, different materials and techniques are used to draw pictures. The aim of this therapy is to make the autistic person more flexible and relaxed and to improve communication skills, self-image and learning skills. The effects of the therapy can be long lasting and transferred to the school, work or home setting.

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