Pervasive Developmental Disorders

Gaining much public exposure through the 1980s movie, Rainman, Autistic
Disorder is now a ubiquitous topic in both academic journals and in the popular
news. Despite increasing exposure to information and lifestyle stories relating to
Autistic Disorder and other Pervasive Developmental Disorders, these labels
continue to garner confusion among the general public. This article will attempt to
define, at a broad level, a group of related disorders known as Pervasive
Developmental Disorders. The information is based on lectures by Emily Rubin,
MS, CCC-SLP that incorporate information from the Handbook of Autism and
Pervasive Developmental Disorders,
2nd Ed. (D. Cohen & F. Volkmar, 1997).

Pervasive Developmental Disorder (PDD) is actually an umbrella term for the
following disorder subtypes: Autistic Disorder, PDD-Not Otherwise Specified
(PDD-NOS), Rett’s Syndrome, Childhood Disintegrative Disorder (CDD), and
Asperger’s Syndrome. Common to all of these subtypes are impairment in social
interaction, impairment in verbal and nonverbal communication, and exhibition of
a restricted and repetitive set of behaviors. The disorders differ in terms of
etiology, age of onset/diagnosis, intellectual functioning, neuropsychological
profile, and prognosis. General characteristics of each subtype will be briefly
discussed based on the Diagnostic and Statistical Manual of Mental Disorders,
4th Ed. (American Psychiatric Association, 1994).

In Autistic Disorder, one sees difficulties with social interaction and
communication as well as stereotypic patterns of behavior. Social interaction is
characterized by impaired nonverbal communicative behaviors (e.g. gestures),
impaired ability to share attention or direct another’s attention to an object or
event of joint interest, and difficulties forming friendships with peers.
Communication impairments include delays in intentional verbal and nonverbal
communication; difficulty initiating and maintaining a conversation; scripted,
rote, or repetitious verbal language; and, limited imaginary play. Stereotypic
patterns of behavior such as the following exist: atypical preoccupations and/or
behavior patterns; preoccupation with sameness and routine; and, stereotypic
motor mannerisms (e.g. flapping hands). These characteristics may present with
varying degrees of severity among those with autistic disorder.

The diagnosis of PDD-NOS often causes great confusion. This subtype, unlike the
others, is not a uniform clinical entity. This diagnosis can characterize a wide
variety of people with vastly different ranges of functioning. People with PDDNOS
demonstrate significant difficulty developing reciprocal social interaction,
significant difficulty communicating–both verbally and nonverbally, and also
exhibit stereotypic behaviors. The criteria, however, are not met for a specific
subtype of PDD. Delays in social development are often noted first in this group
of people rather than a glaring language delay.

Rett’s Syndrome, a PDD typically seen in females, is severe due to the progressive
nature of the disorder. There is a period of stagnation and deterioration of
cognitive and daily living skills starting around 5 to 8 months of age. At that time,
head growth decelerates, purposeful hand skills diminish and stereotypic hand
movements emerge, and coordination of trunk and gait movements diminish.
The intellectual impairment, language and cognition, is more severe than that seen
in severe cases of autism.

Childhood Disintegrative Disorder (CDD) is characterized by normal
development until at least age two at which point a regression of skills begins.
The child then develops characteristics of autistic disorder. A loss of skills occurs
in at least two of the following competencies: social interactions, communicative
functioning, play skills, motor skills, and bowel/bladder control. Prognosis for
CDD is sometimes worse than that of autistic disorder.

Asperger’s Syndrome is characterized by seemingly normal language and
cognitive development; however, non-verbal learning disabilities generally occur
in this population. This disability involves impaired expressive and receptive
nonverbal communication, which includes but is not limited to impaired use and
understanding of facial expressions, gestures, and intonation which can affect a
person’s ability to decipher and participate effectively in social situations. The
person with Asperger’s Syndrome not only has difficulties deciphering nonverbal
cues but also has related difficulties with perspective-taking and empathizing.
This is related to the tendency to intellectualize emotions. Children with
Asperger’s have often been described as “little professors” due to the verbosity
and pedantic style of speech characteristic of the disorder. This label also stems
from the development of a narrow and specific field of interest that tends to
dominate the person’s conversation due to extensive knowledge in the area.

This circumscribed interest is one of the characteristics claiming to distinguish
Asperger’s Syndrome and Autistic Disorder. Another factor possibly
differentiating the disorders is the neuropsychological profile. Those with
Asperger’s seem to show a significantly higher Verbal IQ than Performance IQ;
those with High Functioning Autism seem to show a slightly higher Performance
IQ than Verbal IQ. Some have also made the following generalization: those with
Asperger’s Syndrome are “people-oriented” but lack the ability to attend to and
process the social information necessary for being successful with people; those
with Autism are more “object-oriented.” Given these differences, teaching
strategies would differ for these two populations with one style being more
verbally mediated and the other depending heavily on visual supports. Still, many
experts in the field claim the only difference between the two disorders to be the
label. Fundamental differences over the diagnostic criteria for these disorders
have made it difficult for research studies to use consistent and commonly
accepted subject pools; therefore, the research findings are often the subject of

This broad description of Pervasive Developmental Disorders is designed only to
provide basic information regarding the subtypes of which it is comprised.
Medical professionals, psychologists, and speech-language pathologists are
generally good sources for information on PDD. Please refer to the links on this
website and the list of the suggested readings to learn more about PDD and its