Understanding Autism and Other Pervasive Developmental Disorders such as Asperger Syndrome & Childhood Disintegrative Disorder


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ASD Resources

Understanding Autism


What is autism?

Autism is a complex developmental disability that typically appears during the first three years of life. The result of a neurological disorder that impacts the functioning of the brain, autism impacts the normal development of the brain in the areas of social interaction and communication skills.

The core deficits of autism are:

  • Cognition
  • Communication
  • Social Interactions
  • Repetitive Behaviors

Autism affects human behaviors such as verbal and non-verbal communication, the ability to effectively express ideas and feelings, imagination, leisure and play activities, and establishment of relationships with others.  It generally has a life long affect on how individuals learn to be social beings, care for themselves and participate in their community (National Research Council 2009).

Individuals with autism tend to focus on details, interpret fragments of the information, misperceive the perspective of others and become stuck on one mode of thinking and behaving.  As a result, they misinterpret their experiences.

Pervasive Developmental Disorders

Autism is one of five neurological disorders coming under the umbrella of Pervasive Developmental Disorders (PDD).  A Pervasive Developmental Disorder is a condition that permanently and adversely affects all aspects of a person’s development (Rowland Barret PhD April 2009), including:

  • Social development
  • Cognitive development (intelligence, language)
  • Affective development (mood, emotions)
  • Physical development (motor skills)

The five disorders under PDD are:

  1. Autistic Disorder
  2. Asperger Syndrome
  3. Childhood Disintegrative Disorder (CDD)
  4. Rett's Disorder
  5. PDD-Not Otherwise Specified (PDD-NOS)

Each of these disorders has specific diagnostic criteria as outlined by the American Psychiatric Association (APA) in its Diagnostic & Statistical Manual of Mental Disorders (DSM-IV-TR).

Asperger Syndrome

Asperger Syndrome is “…characterized as a triad of impairments affecting: social interaction, communication, and imagination, accompanied by a narrow, rigid repetitive pattern of activities” (Lorna Wing 1998).

Individuals with Asperger Syndrome tend to have an average to above average IQ, and while they do not exhibit significant language delay, they may demonstrate odd or deviant development in language, and experience difficulty communicating ideas and controlling their emotions.  Other common symptoms of Asperger Syndrome include fascination with a topic that is unusual in intensity or focus, delay in social maturity and social reasoning, and unusual profiles of learning abilities (Tony Atwood 2007).

Childhood Disintegrative Disorder (CDD)

Childhood Disintegrative Disorder, also sometimes abbreviated as CHDD, is a very rare condition appearing in three or four year old children who have developed normally until age two. Over several months, the child will deteriorate in intellectual, social, and language functioning from previously normal behavior. This long period of normal development before regression helps differentiate CDD from Rett syndrome (and in fact it must be differentiated from autism in testing). The cause for CDD is unknown (thus it may be a spectrum disorder) but current evidence suggests it has something to do with the central nervous system.

Rhett's Disorder

Rhett’s disorder is a relatively rare condition with a prevalence of one out of 10,000 to 15,000 individuals that almost exclusively affects females.  After a period of normal development, autism-like symptoms begin to appear in an individual between the age of six months and 18 months, and the child’s mental and social development regresses.  Those who were able to speak stop, they no longer respond to their parents, and they pull away from any social contact.

Some of these early symptoms may be confused with autism.  In the past, Rhett syndrome was sometimes classified as an autistic spectrum disorder; however, today most scientists agree that Rhett syndrome is a separate developmental disorder and not part of the autistic spectrum.  Scientists sponsored by the National Institute of Child Health and Human Development have discovered that a mutation in the sequence of a single gene causes Rhett syndrome, and can physically test for it with an 80 percent accuracy rate.

Some of the problems associated with Rhett syndrome can be treated. Physical, occupational, and speech therapy can help with problems of coordination, movement, and speech.

Prevalence of Autism

Autism is the fastest growing developmental disability in the United States and the most common of the Pervasive Developmental Disorders. The latest numbers released by the Centers for Disease Control and Prevention on March 28, 2014 estimate that 1 in 68 U.S. children has been diagnosed with an autism spectrum disorder. This marks a 30 percent increase from the agency's last report, issued in 2012.

The overall incidence of autism is consistent around the globe, but is four times more prevalent in boys than girls. Autism knows no racial, ethnic, or social boundaries, and family income, lifestyle, and educational levels do not affect the chance of autism's occurrence.


Autistic spectrum disorders are not simple to diagnose, and it’s extremely important to obtain a diagnosis from a qualified professional.  There aren’t any medical tests that can detect autism at the present time; however, this will likely change as brain imaging and genetic testing enable us to look beyond symptoms to the underlying biology (James Coplan, M.D. 2010).  Professionals equipped to accurately diagnose ASD include: developmental pediatricians, child neurologists, child psychologists or child psychiatrists.

A universal criterion to diagnose ASD does not yet exist and approaches may differ depending on the expert’s area of specialization.  Physicians’ diagnoses typically rely on a combination of clinical observation, parental history and application of the DSM IV criteria published by the American Psychiatric Association.  Elements you can expect to see covered in a physician’s evaluation include:

  1. Medical history
  2. Family history
  3. Social history
  4. Physical exam
  5. Neurodevelopment testing
  6. Review of outside records
  7. Lab testing
If an ASD seems plausible

If you suspect that your child may have an ASD, schedule an appointment with his/her primary care physician as soon as possible.  Explain your concerns to the receptionist when you call to book it so your doctor will can allocate proper time for your appointment.

It’s important to understand that although there is no cure for ASDs, research demonstrates that obtaining early intervention treatment services can lead to better outcomes for your child.  The sooner you obtain an accurate diagnosis, the sooner you will be able to understand your child’s needs and develop appropriate plans to address them.

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