The Autism Spectrum – A Layman’s Guide to the World of Autistic Disorders

Key Facts:

Autism is the term used to describe a group of related disorders as well as one specific disorder within the group.

There is a lot of variation. No two individuals with autism will exhibit the exact same symptoms.

Autism is four times as prevalent in boys than in girls.

There are many confusing terms being used to describe the numerous psychological conditions and behaviors which are now referred to as autism spectrum disorders. We will attempt to clarify and correct some of these terms to arrive at a clearer understanding of the autism spectrum.

What is Autism?

Autism is a severe developmental disorder that begins at birth or within the first two-and-a-half years of life. Most children with autism usually are perfectly normal in appearance, but spend their free time occupied in confusing and upsetting behaviors which are noticeably different from those of typical children their age, such as hand-flapping, repetitive actions, head banging and other potentially injurious behaviors.

Our understanding of Autism Spectrum Disorders has advanced rapidly in recent years. Autism spectrum disorders (ASDs) are a family of neurodevelopmental conditions characterized by unusual patterns in social interaction, communication, and range of interests and activities. While this profile is generally applicable for the entire ASD population, much variation actually exists. No two individuals exhibit the same symptoms of this disorder.

In 2007, the Centers for Disease Control reported that 1 in 150 children are diagnosed with autism. Boys outnumber girls four to one.

Pervasive Developmental Disorder (PDD)

Pervasive developmental disorders (PDD) refers to a group of five disorders characterized by delays in the development of multiple basic functions including socialization and communication.

Pervasive developmental disorder not otherwise specified (PDD-NOS), which includes atypical autism, and is the most common;

Autism, the best-known;

Asperger syndrome;

Rett syndrome; and

Childhood disintegrative disorder (CDD).

The label PDD (Pervasive Developmental Disorder) is poorly understood, confusing, and disliked. PDD-NOS is often incorrectly referred to as simply “PDD.” The term PDD refers to the class of conditions to which autism belongs. PDD is not itself a diagnosis, while PDD-NOS is a diagnosis. To further complicate the issue, PDD-NOS can also be referred to as “atypical personality development,” “atypical PDD,” or “atypical Autism.”

In the Autism Research Review International (ARRI) (1991, Vol. 5, No. 2), 16 prominent European and US professionals in the field signed a statement titled “Autism is not necessarily a pervasive developmental disorder.”

The authors indicated that even though the expression PDD had been widely in use at that time for more than a decade ago, it is was not well understood even by many professionals in the field, as well as lay people. They also claim that the term “pervasive” is inaccurate, noting that autism has distinct characteristics, well defined by deficits in social and cognitive performance.

The continued ambiguous and inappropriate use of the term PDD has serious adverse consequences. It has resulted in children and adults with autism tagged with the PDD label being excluded from programs and services for those with autism, which would greatly benefit them.

There are many more children with autistic-like disorders than there are children with autism itself. The most accurate definition for this category would be “children with severe disorders of communication, socialization and behavior.” The need for a more accurate all-encompassing title for this group has been evident for almost two decades, and the continued use of the obsolete terminology has hindered efforts aimed at creating better understanding and progress.

Of the various labels that have been recommended to substitute for PDD, the one that has won the most acceptance is “autism spectrum disorder,” which was first recommended by Wing and Gould in 1979. This terminology acknowledges that autism is comprised of a series of disorders whose full extent may not yet be known to us.

Autism Spectrum Disorder (ASD)

This is the main group of conditions that typically goes by the name of “autism.” Unfortunately, many people use the word autism to refer to both the entire autism spectrum and the specific disorder to which the term was originally applied.

Although autistic disorder is a diagnosis, it is a broad one. There are so many different disorders within that diagnosis that the label itself means little, from a treatment point of view. It is much more helpful to describe each child’s distinctive pattern of developmental strengths and weaknesses.

Here is a more specific set of definitions of disorders which are part of the autism spectrum:

Asperger’s Syndrome

Asperger’s syndrome is a developmental disorder in which people have severe difficulties understanding how to interact socially.

People with Asperger’s syndrome have some traits of autism, specifically very poor social skills and a tendency for sameness and habit.

However, unlike those diagnosed with what we will call classic autism, children with Asperger’s syndrome do not exhibit the full range of autism’s developmental delays. For example, they typically start to talk around 2 years of age and have normal to above-normal intelligence for children their age.

On average, these children have normal speech patterns, but exhibit many “autistic” social and behavioral problems.

Related autism disorders

In the last five to eight years, research has shown that many people who engage in autistic behaviors have related but distinct disorders. These include: Asperger Syndrome, Fragile X Syndrome, Landau-Kleffner Syndrome, Rett Syndrome, and Williams Syndrome.

Asperger Syndrome is characterized by concrete and literal thinking, obsession with certain topics, excellent memories, and ‘eccentric’ behavior. Individuals with Asperger’s are considered high-functioning and are capable of holding a job and of living independently.

Fragile X Syndrome is a form of mental retardation in which the long arm on the X chromosome is constricted. Roughly 15% of people with Fragile X Syndrome show evidence of autistic behaviors. These behaviors consist of: delay in speech/language, hyperactivity, poor eye contact, and hand-flapping. The majority of these individuals function at a mild to moderate level. As they grow older, their unique physical facial features may become more prominent (e.g., elongated face and ears), and they may develop heart problems.

People with Landau-Kleffner Syndrome also exhibit many autistic behaviors, such as social withdrawal, persistence on sameness, and language problems. These individuals are often thought of as having ‘regressive’ autism because they appear to be normal until sometime between ages 3 and 7. They often have good language skills in early childhood but gradually lose their ability to talk. They also have abnormal brain wave patterns which can be diagnosed by analyzing their EEG pattern during an extended sleep period.

Rett Syndrome is a degenerative disorder which affects mostly females and usually develops between 1/2 to 1 1/2 years of age. Some of their characteristic behaviors include: loss of speech, repetitive hand-wringing, body rocking, and social withdrawal. Those individuals suffering from this disorder may be severely to predominantly intellectually challenged.

Williams Syndrome is characterized by several autistic behaviors including: developmental and language delays, sound sensitivity, attention deficits, and social problems. In contrast to many autistic individuals, those with Williams Syndrome are quite sociable and have heart problems.


While there is no known distinctive cause of autism, there is increasing proof that autism can be caused by a series of problems. There is some indication of a genetic influence in autism. There is a greater likelihood that identical twins will have autism than fraternal twins. In the case identical twins, there is a 100% overlap in genes; whereas in fraternal twins, there is a 50% overlap in genes, the same overlap as in non-twin siblings.

Currently, a great deal of research has focused on locating the ‘autism gene;’ however, many researchers speculate that in the end, three to five genes will likely be associated with autism. There is also evidence that the genetic link to autism may be a weakened or compromised immune system. Other research has shown that depression and/or dyslexia are quite common in one or both sides of the family when autism is present.

There is also evidence that a virus can cause autism. There is an increased risk in having an autistic child after exposure to rubella during the first trimester of the pregnancy. Moreover, there is also an increasing fear by parents that viruses associated with vaccinations, such as the measles component of the MMR vaccine and the pertussis component of the DPT shot may cause autism. However, there is no known research that supports this assumption.

There is mounting concern that toxins and pollution in the environment can also lead to autism. There is a high prevalence of autism in some parts of California, various areas in Queens and Staten Island, as well as certain parts of New Jersey. Several agencies are now attempting to uncover the reasons for the high percentage of autism in this community, which may be related to environmental conditions.

What is the Outlook?

Intervention has a direct impact on outcome–typically, the earlier a child is treated, the better the diagnosis will be. In recent years there has been a noticeable increase in the proportion of children on the autistic spectrum who can attend school in a typical classroom and live semi-independently in community settings. However, the majority of individuals with autism remain impaired in their ability to communicate and socialize.

The number of autism cases has risen recently mostly because doctors now apply a broader definition of the disorder and have better diagnostic tools. Yet autism remains a mystery and there are still many unanswered questions. Hopefully this article will give the reader a better understanding of what we know about autism today, including its many sub-categories, and remove the confusion created by the use of misleading terminology to describe this dreaded disorder.