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Characteristics of PDD

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Characteristics of Autism and
the Pervasive Developmental Disorders (PDD)

What are the Pervasive Developmental Disorders?

The Pervasive Developmental Disorders or Autism Spectrum Disorders (ASD) are a group of developmental disabilities, which according to recent estimates, affect as many as 1 out of every 68 people.  The Pervasive Developmental Disorders are also known as the autism-spectrum disorders, and they include Autistic Disorder, Pervasive Developmental Disorder-Not Otherwise Specified (PDD-NOS), Asperger’s Disorder, Rett’s Disorder, and Childhood Disintegrative Disorder.  They affect up to 4-5 times as many boys as girls, occur in all cultures, and are present among all socioeconomic classes.  They usually become noticeable between the ages of 1 and 3 years, and affect the way in which social behavior, communication (verbal and nonverbal communication), and attention/interests develop.  There is a wide spectrum of impairment associated with the Pervasive Developmental Disorders, which can range from mild to severe.  The PDDs do not describe a delay in development, but rather a difference or deviation in development in these three areas.

What causes Pervasive Developmental Disorders?

Pervasive Developmental Disorders are neurologically-based, medical disorders that are not caused by errors in parenting, a specific environmental toxin, poor prenatal care, etc.  In a percentage of cases, there may be a genetic cause.  Although scientists are making strides in identifying their cause(s), right now, there does not appear to be one specific cause for all cases.  A physician or psychologist may diagnose one of these conditions using a medical model (following the criteria set forth in the Diagnostic and Statistical Manual-Fourth Edition, DSM-IV).  Alternatively, an education team may assign an educational eligibility (autism), based on a child's special needs for educational modifications.  At the present time, there is no medical test that indicates an autism spectrum disorder; however, routine medical screenings (metabolic, genetic, and Fragile X) are recommended to rule out the presence of another identifiable condition.  In either case, the diagnosis of a PDD is based on behavioral observations and clinical experience. 

What is the difference between Autism and PDD-NOS?

Pervasive Developmental Disorder is a general category used to describe a pattern of behavioral differences (which may include deviations, excesses, or difficulties) in the areas of social relating, communication, and attention/interest.  Children who demonstrate a number of characteristics or symptoms in these three areas, and whose problems are not better explained by other disorders, may receive a diagnosis of PDD.  This diagnosis may also be applied if the child exhibits a variety of symptoms associated with Autism, but in an unusual pattern.  It should be stressed that this is still a relatively new label, dating back only 15 years, so that some professionals may not be familiar with its correct use.  In some cases, it has been incorrectly used synonymously with "significant developmental delay” or “general delay" or "developmental delay."  Both Autism and PDD-NOS can occur in conjunction with a wide spectrum of intellectual ability.  The defining feature must be a qualitative difference in social and language development for these diagnoses.

Autism and PDD-NOS are subtypes of the Pervasive Developmental Disorders.  It is common for a person to be given the general diagnosis of PDD, which indicates an autism spectrum disorder without clarifying the exact form of PDD.  The differential diagnosis of the PDDs is based on a particular pattern or clustering of symptoms, and specific criteria on the number of symptoms that are observed.  In both disorders, there is a higher likelihood of developing seizures than in individuals without autism.

How do professionals tell the difference between autism and PDD-NOS?

Primarily by the pattern and degree or number of characteristics observed or reported. However, there are difficulties associated with this differential diagnosis, and it often takes a clinician with extensive experience with both disorders to make the call. 

Problems may occur when a child's developmental level is quite low, so that assessing the areas of concern would be quite difficult at a similar age equivalent.  A second problem occurs with children who are toddlers and young preschool-age children.  Many of the behaviors that are considered crucial for diagnosis are still very variable in typically developing young children in this age range.  Some children may receive a diagnosis of PDD-NOS as a toddler because they did not have any communicative behavior; later they may qualify for a diagnosis of autism as their communication develops and it becomes more evident that a qualitative difference exists in that area. For parents and educators, the important thing to focus on is not the specific label a child receives, but what can be done to help the child develop skills in the areas of concern.

What is the difference between Autism and Asperger’s Disorder?

Asperger’s Disorder was only added as a subtype of the PDDs in the DSM-IV in 1994, so its characteristics are still under a great deal of study.  Similar to distinguishing Autism from PDD-NOS, there are specific criteria that distinguish Autism and Asperger’s.  Some of the key differences between Autism and Asperger’s are that the individual could not have had a clinically significant language delay (although unusual patterns of communication and impaired nonverbal communication is generally present), and the individual must function within average to above average intellectual (cognitive) levels.  There is currently much debate between professionals whether Asperger’s Disorder should really be distinguished from high-functioning Autism, and clinical experience is often important to determine how these diagnoses should be applied to a particular individual.

Does my child have an intellectual impairment (mental retardation)?  How is this different from Autism?

Intellectual impairment (mental retardation) is a term used to describe individuals who follow a slower developmental path than others their age.  “Intellectual impairment” is the term generally used by educators and “mental retardation” is the term used in the DSM-IV; however, these terms generally refer to the same types of learning difficulties.  People with an intellectual impairment continue to develop skills and abilities as they grow, although they typically progress more slowly than their peer group.  Intellectual Impairment is identified by comparing a person's intellectual performance on standardized tests with others in his/her age group, and by looking at how well that individual can function in adaptive skills (self-care, safety knowledge, independent living skills).

Autism and PDD-NOS can be present in people who also have an intellectual impairment; however, they can also be present in individuals who have superior intellectual skills.  It varies from individual to individual.  However, because communication skills are an integral part of what most people consider intelligence, the problems people with autism show in this area may affect their ability to perform on standardized intelligence tests.  Some individuals with Autism may receive a diagnosis of intellectual impairment or mental retardation due to suppressed performance in areas involving verbal expression or understanding, while performing above average in some other areas (such as memory and visual problem-solving).  In such cases, the term is not particularly meaningful or predictive of long-term outcome.

When assessing the skills of a child with a PDD, it is important to evaluate the skills that they show on an everyday basis in situations that are meaningful and familiar to them.  Evaluation should not only focus on identifying a child’s intellectual level, but should aim to identify the child’s learning characteristics so that meaningful goals can be planned to help the child develop to his or her potential. 

What is the long-term prognosis for children diagnosed with Autism/PDD-NOS?

Autism/PPD-NOS is a life-long disability, and individuals with Autism live a full lifetime.  There are no cures, and even those individuals who proclaim themselves "recovered" continue to have difficulties with subtle social processes.   However, with advances in education, early intervention, and research, today individuals with Autism/PDD have a greatly expanded range of outcomes as adults.  In the past, the majority of individuals with Autism lived in institutional care as adults.  Current trends, based on increased knowledge of how to educate children with Autism and the importance of early education, emphasize building skills and abilities in order to prepare young adults with Autism/PDD to work, to live in the community, and in some cases, to pursue higher education.  Outcome appears to depend on both degree of overall impairment and intensity of educational/treatment effort.  Prognosis is markedly better for individuals who develop verbal language before the age of 5 years

My doctor says my child will never learn to talk.  Is this true?

For most children with Autism, there is no physical reason to preclude learning to use verbal communication.  Unless there is a specific physical problem (such as deafness, absence of larynx/pharynx, focal lesion the brain), there is no reason to make such an assumption.  It should be noted that speech does not frequently come easily to individuals with Autism, and research suggests that intensive efforts and education are often needed for children with Autism to develop speech.  However, given the relationship between speech development and prognosis, aggressively pursuing verbal communication skills is highly recommended for young children with Autism/PDD-NOS.

How is Autism/PDD-NOS diagnosed?  What are the areas of concern?

Individuals with Autism frequently display certain clusters of behavior that distinguish them from individuals who do not have Autism.  Diagnosing this syndrome using the DSM-IV involves consideration of the following characteristics.

Note:  The child need not show all of these characteristics.

I. Qualitative impairment in reciprocal social interactions:
This refers to a developmental difference in the individual's interest and competence in achieving reciprocal interactions.  It does not mean that the individual is not affectionate, or cannot make contact with other people, or is simply behind schedule in the development of social skills. What is different is the quality of interaction and interest.

Behaviors suggesting this area may be affected include:

  • difficulty understanding/perceiving the emotions of others 
  • difficulty sustaining interactions initiated by others
  • poor, fleeting or abnormal eye contact
  • lack of comfort-seeking when distressed
  • difficulty making peer friendships appropriate to developmental level
  • lack of social or emotional reciprocity
  • lack of effort to share interests or enjoyment with others (may not show, point out or bring objects to share with others)
  • in preschool children, lack of turn-taking play with peers (although the child may enjoy active and rough-and-tumble play)
  • difficulty understanding social cues
  • difficulty understanding and expressing his/her own emotions
  • seeking touch and affection on own terms, but shunning affection when offered by others (not on own terms)
  • preference for solitary play instead of group or paired play
  • absence of symbolic play behavior, very literal and concrete in comprehension (e.g., would not use a block as a telephone)
  • frequent or sustained giggling, laughing or crying without visible cause
  • may appear deaf at times, yet hear sounds from a distance at other times (ignore voice when name is called, yet run to window when ice cream truck is two blocks away)

II. Qualitative impairment in verbal and non-verbal communication and imaginative activities:
Again, this does not refer to a delay in development, but rather a difference in the way verbal and nonverbal communication proceeds.  Behaviors suggesting this area may be affected include:

  • normal development of early babbling and first words which are later lost between the ages of 1 and 3 years, while other development appears to proceed on course
  • difficulty developing verbal communication
  • pulling adults to items of interest rather than pointing or gesturing
  • lack of use of gestures, demonstration, mime to compensate for lack of verbal expression
  • repeating phrases verbatim frequently (echolalia)
  • repeating phrases (often from TV) out of context after a period of time has passed (delayed echolalia)
  • using words out of communicative context (walks around saying "hi daddy" when daddy is at work, and nobody is present)
  • answering question by parroting question back to you
  • poor timing and content variation in topic
  • difficulty taking turns in maintaining a conversation
  • difficulty with abstract concepts (learns nouns better than verbs or adjectives)
  • difficulty understanding the "theme" of a story
  • inventing own words for objects and rigidly uses them (neologism)
  • talking mainly about one restricted topic, or using one word repeatedly (perseveration)
  • acting as if adults can read his/her mind
  • question-like or sing-song cadence to their speech
  • difficulties in imitation

III. Restricted repetitive and stereotyped patterns of behavior, interests, and activities:

  • engaging in repetitive non-functional body movements (for example, spinning or whirling
  • around, flapping arms or hands, rocking, walking on tiptoes, looking at fingers (stereotypies)
  • difficulty with changes or transitions
  • under- or over-sensitivity to sensory stimuli (sounds, lights, textures, odors)
  • restricted food preferences, sometimes related to food texture
  • may explore environment in unusual ways (smelling objects, mouthing excessively, scratching, licking)
  • develop attachments to objects that are not typical for children (must sleep with twigs) 
  • may carry around objects without ever playing with them, and become upset when they are taken away 
  • becomes fascinated with parts of objects (wheels, lines, writing)
  • may spin objects that are round in shape
  • may focus on ordering and reordering or categorizing toys instead of playing with them (lining up cars, amassing red blocks)
  • plays with materials in the same sequence across a period of time where variation would be expected (has Ernie follow same route to hospital every time he plays with car mat)
  • develops routines that are difficult to break
  • may get upset over trivial changes in environment (moving a lamp)
  • not interested in a wide variety of toys and materials
  • peculiar insistence in selected items, sequences, or routines (will only drink milk out of a certain cup)
  • does not ask for help, but figures out how to get what he/she wants


  • eating inedible objects
  • undersensitive to pain
  • attention span fleeting for most activities, yet can spend long periods of time focused on one activity of his/her own interest (can watch videos for hours, but can't sit for 30 seconds for other tasks)
  • high overall activity level
  • may need less sleep than typical children of the same age
  • absence of fear or appreciation of dangerous situations
  • self-injurious behavior that does not appear to be directed at achieving any result (head banging, eye poking, biting)
  • uneven intellectual ability (skills show a great deal of variability)
  • peculiar fascination with one specific medium (country music, TV station, Wheel of Fortune, preview guide), etc.
  • more interested in credits and commercials than TV shows
  • unusual fear reactions


  • good memory, especially for visually presented information
  • enjoys completing tasks with a set end point
  • may have precocious interest in letters and numbers
  • cuddly and affectionate with parents, usually on own terms
  • mechanical aptitude (can program the VCR at age 2)
  • higher skills/talents in art, music, math, balance
  • enjoy vestibular stimulation (tosses, being turned upside down, etc)
  • stamina
  • good non-verbal problem solving abilities (can get what they want)

What should I do about my child's Autism/PDD-NOS?
 The most successful approach to dealing with the symptoms of Autism involves systematic and intensive educational programming. You may want to pursue a second opinion regarding diagnosis; however, the most prudent approach is to assume that the diagnosis is correct and proceed to develop plans to deal with the language and social difficulties of the child through educational programming (including speech therapy, therapeutic play groups, etc.) while you are also looking for a second opinion.  If the original diagnosis was incorrect, no valuable time will be lost.  The Emory Autism Center is available at (404) 727-8350 to provide you with information, referrals, evaluations, and recommendations for your child.