What is Autism Spectrum Disorders (ASD)?

Autism Spectrum Disorders include autism and related disorders such as Asperger Syndrome, Rett Syndrome, childhood disintegrative disorder, and pervasive developmental disorder-not otherwise specified (PDD-NOS).

Autism

The most common definition of autism appears in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition-Text Revision (DSM-IV-TR; American Psychiatric Association, 2000).

DSM-IV-TR Definition

Autism is one of the pervasive developmental disorders included in the DSM-IV-TR criteria. It refers to the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activities and interests.

Educational Definition (Individuals with Disabilities Education Act, or IDEA 2004)

Autism is a developmental disability that significantly affects verbal and nonverbal communication and social interaction. It is generally evident before age 3 and adversely affects a child’s educational performance. Other characteristics often associated with autism include engagement in repetitive activities and stereotyped movements, resistance to environmental change or change in daily routines, and unusual responses to sensory experiences.

Autism does not apply if a child’s educational performance is adversely affected primarily because the child has an emotional disturbance.

A child who manifests the characteristics of autism after age 3 may be identified as having autism.

Asperger Syndrome/High-Functioning Autism

The main characteristic of Asperger Syndrome is impairment of social interaction. Asperger Syndrome first appeared in the DSM-IV in 1994, 50 years after the Austrian physician Hans Asperger published his first paper on ‘autistic psychopathy’ in 1944.

The relationship between Asperger Syndrome and high-functioning autism is still controversial. Even though high-functioning autism is not an official diagnosis, many professionals still use the terms Asperger Syndrome and high-functioning autism interchangeably because of a lack of information differentiating the two.

The DSM-IV-TR diagnostic criteria for Asperger Syndrome include qualitative impairment in social interaction, and restricted repetitive and stereotyped patterns of behavior, interests, and activities. There is no specific diagnostic criteria for high-functioning autism.

Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS)

According to the DSM-IV-TR, this category includes atypical autism and should be used when there is a severe and pervasive impairment in the development of reciprocal social interaction or verbal and nonverbal communication skills, or when stereotyped behavior, interests, and activities are present, but the criteria are not met for a specific pervasive developmental disorder such as autism, Asperger Syndrome, schizophrenia, schizotypical personality disorder, or avoidant personality disorder. For example, this category includes individuals who do not meet the criteria for Autistic Disorder because of late age of onset.

Pervasive Developmental Disorders (PDD)

The term PDD is widely used by professionals to refer to children with autism and related disorders. The DSM-IV-TR includes autism and other developmental disabilities such as Rett Syndrome, Childhood Disintegrative Disorder, PDD-NOS, and Asperger Syndrome under the PDD category. Therefore, PDD is not a specific diagnosis but a broad term that includes various conditions.

Prevalence of ASD

The prevalence of ASD is increasing. Recent research shows 1 in 150 individuals have ASD (Autism Society of America, 2007 http://www.autism-society.org; Centers for Disease Control and Prevention, 2007). This means that as many as 1.5 million Americans are believed to have some form of ASD. Based on statistics from the U.S. Department of Education and other governmental agencies, autism is growing at a rate of 10-17 % per year. The 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 the occurrence of autism.