- Definition & Incidence
Autism and Pervasive Developmental Disorder-NOS (not otherwise specified)
are developmental disabilities that share many of the same characteristics.
Usually evident by age three, autism and PDD-NOS are neurological disorders
that affect a child’s ability to communicate, understand language, play,
and relate to others.
In the diagnostic manual used to classify disabilities,
the DSM-IV (American Psychiatric Association, 1994), “autistic disorder”
is listed as a category under the heading of “Pervasive Developmental
Disorders.” A diagnosis of autistic disorder is made when an individual
displays 6 or more of 12 symptoms listed across three major areas: social
interaction, communication, and behavior. When children display similar
behaviors but do not meet the criteria for autistic disorder, they may
receive a diagnosis of Pervasive Developmental Disorder-NOS (PDD not otherwise
specified). Although the diagnosis is referred to as PDD-NOS, throughout
the remainder of this fact sheet, we will refer to the diagnosis as PDD,
as it is more commonly known.
Autistic disorder is one of the disabilities specifically
defined in the Individuals with Disabilities Education Act (IDEA), the
federal legislation under which children and youth with disabilities receive
special education and related services. IDEA, which uses the term “autism,”
defines the disorder as “a developmental disability significantly affecting
verbal and nonverbal communication and social interaction, usually evident
before age 3, that adversely affects a child’s educational performance.
Other characteristics often associated with autism are engagement in repetitive
activities and stereotyped movements, resistance to environmental change
or change in daily routines, and unusual responses to sensory experiences.”
(In keeping with the IDEA and the way in which this disorder is generally
referred to in the field, we will use the term autism throughout the remainder
of this fact sheet.)
Due to the similarity of behaviors associated with
autism and PDD, use of the term pervasive developmental disorder has caused
some confusion among parents and professionals. However, the treatment
and educational needs are similar for both diagnoses.
Autism and PDD occur in approximately 5 to 15 per 10,000 births. These
disorders are four times more common in boys than girls.
The causes of autism and PDD are unknown. Currently, researchers are investigating
areas such as neurological damage and biochemical imbalance in the brain.
These disorders are not caused by psychological factors.
Adapted from information
published by the National Information Center for Children and Youth with Disabilities