What is Autism?

Since we first launched OAARSN in early 2000, this question is asked much more frequently, as popular interest and research have increased. But it is no easier to answer in 2009 than it was then.

Autism is a very confusing diagnostic label. The term is used both for a more specific syndrome of abnormal development and also for a much broader range of related disorders. As their causes are not yet known, these disorders are defined in terms of sets of behavioural symptoms which are not the same in every affected person. If we were to enter a room full of persons who had been diagnosed with Autism, we would be struck far more by the differences than by the similarities among them. Websites concerned with Autism usually present some information about the disorders, though some do not make clear the distinction between the more specific Autistic Disorder and the whole spectrum of autism disorders.

A great deal of research into Autism that has been reported since the early 1990s helps us to understand several features more clearly. There is general agreement that, in its full-blown form, Autism involves a triad of impairments-in social interaction, in communication and the use of language, and in limited imagination as reflected in restricted, repetitive and stereotyped patterns of behaviour and activities. People who combine all three impairments to a marked degree have the classic form of Autism, so named by Leo Kanner, a psychiatrist at Johns Hopkins University, in 1943, and termed Autistic Disorder in the Diagnostic and Statistical Manual of Mental Disorders IV (1994). But much larger numbers of people may have some of the traits of Autism.

The idea of a spectrum or continuum of autistic disorders is helpful to include persons who have some if not all the symptoms of Autism, sometimes in combination with other disabilities. Asperger’s Syndrome, defined in 1944 but not widely used as a diagnostic label until the mid-1990s, may affect seven times as many people as Autistic Disorder (classic Autism).

We now know that Autism involves disorders of development of brain functions. It is not a mental illness. Nor is it psychogenic, caused by anything in a child’s psychological environment. Earlier notions, that Autism was caused by emotional deprivation or emotional stress, have long been discredited. Autism affects families in all races, cultures and socioeconomic groups and is found everywhere in the world. More males than females are affected, the ratio being 4:1 with Autistic Disorder (classic autism), 9:1 with Asperger’s Syndrome.

For a diagnosis of Autism, the main symptoms must be clear before the age of 3 years. The disabilities are lifelong and there is no known cure, though careful training and sensitive support can bring improvements. The autistic impairments may be associated with cognitive disabilities. Two-thirds of those with Autistic Disorder (classic Autism or Kanner syndrome) have been assumed to be mildly handicapped in cognition and intellect. Most people with Asperger’s have average to higher IQ. Across the autistic spectrum, perhaps 10 per cent have distinctive abilities—in such fields as art, music, mathematics or memory—and may be called autistic savants. (The proportion of people with such special abilities in the whole population is only one per cent).

How many people have Autism?

Key studies in the 1960s, in sample regions in different parts of the world, found a ratio of 4.5 per 10,000 of the child population to have Autistic Disorder (classic Autism or Kanner’s syndrome). By around 1990, a further 15 in every 10,000 were estimated to have what are sometimes called, in North America, other pervasive developmental disorders.

Research in the 1990s developed the concept of Autism Spectrum Disorders (ASD), with the aim of including people who might have some but not all of the key diagnostic features. British studies of sample regions estimated that 71 in every 10,000 have a milder form of ASD, mainly affecting social relationships rather than communication and language. About half of this larger number (36 in every 10,000 of the population) is estimated to have Asperger’s Syndrome. These figures add up to 91 persons in every 10,000, nearly one per cent of the total population, which is the prevalence usually cited for the United Kingdom. At this rate, more than 60 million people around the world have some form of Autism.

In whole countries, such data are estimates rather than actual counts of people diagnosed. It is likely that many on the Autism spectrum have not been formally identified, especially adults. Prevalence figures of one person in 150 or one in 166 are quoted in North America. Applying the rate of one in 150 to age-groups of Ontario’s population at the 2001 census, we find the numbers in the following table, which may be compared with numbers for the narrower definition of Autistic Disorder.

Ontario: Estimates of Autism Numbers
(2001 Census)

Age group

Autistic Disorder
1 in 2,222

Autism Spectrum
1 in 150

0 – 4 years



5 –14 years



15-19 years



20-24 years



25-44 years



45-54 years



55-64 years



65 + years




Children (0-19) 



Adults (20+)



An interesting and important question is: "Is the prevalence of Autism increasing?" Some people, notably advocates for services to young children, describe the increased diagnoses of some form of Autism during the past 15 years as an explosion, even a pandemic. In part, this probably reflects an enormous increase in awareness of Autism, so that professionals and parents recognize the symptoms of ASD much more readily than they did a generation ago. Another factor is the widening of criteria from Autistic Disorder or classic Autism, to include the much broader concept of an Autism spectrum including Asperger’s Syndrome as well as people who combine Autism with some other disability. Perhaps there has also been a real increase in the numbers and proportions of affected people—related to a wide range of environmental toxins and viral infections.

Another question is: “Does the prevalence of autism vary from place to place?” Autism has been found all over the world, in all societies and cultures, and in people of all ethnic and socio-economic groups. Some localities have been found to have very high concentrations of ASD diagnoses.

Since 2000, the volume of funded research into genetic, environmental and biomedical factors in Autism has increased enormously, but we are not yet able to answer these questions with any certainty.

What causes Autism?

Although they are not yet known, there are strong indications that the causes of Autism Spectrum Disorders are biological. The evidence includes the following observations.

It is extremely unlikely that Autism is caused by a single factor. It is most likely that certain people are genetically predisposed to be sensitive to any of various environmental insults that actually trigger the symptoms that we call Autism. Genetic research has identified several genes that may be mutated or damaged. And all kinds of environmental insults may be involved-from the myriad chemicals used in agriculture, forestry, industry and our homes to substances taken into our bodies as medicines or food. It is likely that Autism may be triggered in different people by varying combinations of genetic and environmental factors. This variability is reflected in the huge variety of particular symptoms and the differences that are so evident among people diagnosed with Autism Spectrum Disorder.

Since the late 1990s, there has been a major push to promote research into the causes of Autism, with commitments by governments and charitable foundations to fund research. Various research centres have been set up, often as consortia of teams at several universities. Research findings are published at a quickening pace, in popular media as well as scientific journals.

Research on autism is welcomed as one sign of increased awareness of very challenging disabilities, after decades of neglect. However, we may be concerned if specialized genetic research may not take enough account of various causes that are needed to explain the distinct types of autism. Or if it is at the expense of study of approaches to treatments, interventions or services that could make help people already living with Autism.

How is Autism diagnosed?

Autism cannot be diagnosed by a simple blood test or brain scan, as some disorders may be. Diagnosis depends on a professional assessment of specific behaviours, usually in the first three years of life. When children are not identified till they are older, diagnosis may rely on parents’ memories, records and videotapes. Adults, not identified when they were children for various reasons, may find that some degree of Autism Spectrum Disorder explains their lifelong sense of being different and perhaps some learning and social diffierences.

Autistic Disorder, as defined by the World Health Organization’s ICD-10 Classification of Mental and Behavioural Disorders (1992), is distinguished into:

North American professionals follow the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, the 4th edition (DSM IV, 1994) still being the current authority. DSM IV distinguishes five subtypes within the broader category it calls Pervasive Developmental Disorders, and prescribes the diagnostic criteria and associated features for each type:

To be diagnosed with Autistic Disorder, a child should show the following behaviours:

I: A total of six (or more) items from (A), (B), and (C), with at least two from (A), and one each from (B) and (C)

(A) Qualitative impairment in social interaction, as manifested by at least two of the following:

(B) Qualitative impairments in communication as manifested by at least one of the following:

(C) Restricted repetitive and stereotyped patterns of behavior, interests and activities, as manifested by at least two of the following:

(II) Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years:

The term Pervasive Developmental Disorders was adopted by some Canadian professionals in the 1990s to include all variants and degrees of Autism recognized then. But other professionals as well as parents and caregivers are not satisfied with some of the labels and language of DSM IV, preferring the term Autism Spectrum Disorder (first used in Britain) which is now more commonly used.

Types of Autism

Several types have been defined along the Autism spectrum, differing in the severity of the symptoms and in the combinations of autistic impairments with other disabilities. We present brief accounts of some of these.

Classic Autism, Autistic Disorder or Kanner’s Syndrome
The psychiatrist Leo Kanner of John Hopkins University first described and named this syndrome based on 11 of his child patients between 1932 and 1943. He noted the following common features:

Kanner’s observations became the criteria for early studies of the prevalence of Autism. Children (and adults) with these features have the full triad of impairments and represent the most severely disabled end of the autism spectrum of disorders.

Autism organizations were first formed in the 1960s and 1970s by the parents of children with classic Autism. More recently these organizations have been enlarged in scope and functions to serve all those with a wider range of symptoms on the Autism Spectrum.

Asperger’s Disorder
First described by Hans Asperger of Vienna in 1944, whose work was not generally known in English translation until 1981, the disorder was not listed in the Diagnostic and Statistical Manual of Mental Disorders (DSM) until 1994.

Asperger’s Disorder shares with Autistic Disorder a severe and sustained impairment in social interaction, and restricted and repetitive patterns of behaviour and interests. But people with Asperger’s do not have the significant delays in language, cognition, self-help skills or adaptive behaviour that are typical in Autistic Disorder. They may be physically clumsy and awkward, more obviously than children with classic Autism. Asperger’s is often not recognized easily or early, and may be misdiagnosed as Tourette’s Syndrome, Attention Deficit Disorder, Attention Deficit Hyperactivity Disorder, Oppositional Defiance Disorder, or Obsessive-Compulsive Disorder. As with Autism, the disorder is lifelong and no complete cure is known. Asperger’s Disorder may be the largest type on the autism spectrum, affecting 35 in every 10,000 people.

Some people with Asperger’s may have an exceptional talent or skill with which they are preoccupied. It is conjectured that several people of remarkable genius may have had Asperger’s--including Albert Einstein, Vladimir Nabokov, Ludwig Wittgenstein, Bela Bartok and Andy Warhol. Of Canadian interest is the possibility that Asperger’s Syndrome could explain Glenn Gould’s social deficiencies, obsessive perfectionism and intolerance of change. This idea was raised in the 1996 biography by psychiatrist Peter Oswald, Glenn Gould: The Ecstasy and Tragedy of Genius and later elaborated by the musicologist Timothy Maloney. Gould was acutely sensitive to light, sound and temperature, and had a phobia about shaking hands as well as a limited range of preferred foods. His bizarre mannerisms as a concert performer could be understood as uncontrollable expressions of Asperger’s.

Rett’s Syndrome
First identified by the Australian Dr Andreas Rett in 1965, Rett’s is a complex neurological degenerative disorder that affects only girls. It is rarer than some of the types on the Autism spectrum, affecting one in every 10,000 girls. From onset at about 18 months of age, its victims become profoundly and multiply disabled, and dependent on others for all their needs. Key symptoms include hypotonia (reduced muscle tone) and such autistic-like behaviours as wringing and waving hands. The discovery of the gene for Rett’s syndrome was reported in October 1999.

Autism in adulthood

How relevant is diagnosis to our focus on adult Autism? For a diagnosis of Autistic Disorder (classic Autism) at least, the behavioral symptoms must be present before age three. Age of onset may be later for some of the rarer forms of Autism. And critical symptoms of some higher functioning forms of Autism, notably Asperger’s, may not become clear until adolescence or adulthood.

Pediatricians and psychiatrists, in the past and perhaps sometimes today, may have been reluctant to pronounce a diagnosis of Autism out of consideration for the parents’ feelings or because such a label was thought to close doors to service rather than open them. So many of today’s adults who probably had key symptoms of Autism in early childhood were given other labels or described as having "autistic tendencies".

Autistic traits usually persist into adulthood, but with a wide range of outcomes. Some adults with ASD achieve college degrees and function independently. Most diagnosed with classic Autism may not develop functional language and communication and may have poor daily living skills throughout their lives. Some adults with Autism who live without support may be reclusive or eccentric. Some may be labeled with obsessive-compulsive disorder, schizoid personality, simple schizophrenia, affective disorder, mental retardation or brain damage.

Those who probably had classic Autism as children may suffer from general assumptions that they have a poor prognosis as adults. It may not seem to professionals and policy-makers that they are worth much in resources. In recognizing other subtypes of Autism Spectrum Disorder, we may tend to overlook the needs of adults with the most distinctive and severe forms of the disorder.

By adulthood, in any case, the original symptoms of Autism may be masked by the person’s life and treatment experiences, the effects of drugs, and her/his own efforts to cope with the disorder. Each person of whatever age should considered as a unique individual. This is especially true of adults who were diagnosed with Autism as children. Their challenges cannot be understood purely and simply in terms of Autism. On the other hand, knowledge of the Autism and past treatments may help in assessing their abilities and challenges as adults and in considering helpful approaches—including adult versions of therapies and strategies that may have been mainly designed for children, but too recently for today’s adults.

In our view, far too little attention is paid to adult Autism as a general category of disability or to individual adults who have the symptoms of Autism. Yet adults with Autism are said to have normal life expectancy. It would be prudent as well as humane to assess each person’s needs and abilities as part of individual plans for supports that will enable them to use their abilities, realize their dreams, and attain the best possible quality of life.

OAARSN’s website is dedicated to the exchange of information about the needs and abilities of adults with Autism Spectrum Disorders, and about the most effective ways to support them to lead good whole lives.

Back to Top