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


What is PDD-NOS, and how is it any different than Autism?


Pervasive Developmental Disorder—Not Otherwise Specified (PDD-NOS) is a pervasive developmental disorder (PDD)/autism spectrum disorder (ASD). PDD-NOS is one of five forms of Autism Spectrum Disorders. PDD-NOS is often referred to as atypical autism.

Many parents experience a lot of confusion about the diagnosis of autism or PDD-NOS. There is even a lot of confusion among physicians and diagnosticians themselves. Some pediatricians have been known to tell parents that “a diagnosis of PDD-NOS is reserved for children on the spectrum who are curable.” Other pediatricians have told parents that “PDD-NOS is not even on the spectrum!” Many clinicians seem to take a milder diagnosis and simply label it PDD-NOS.

Let’s look at Autism first…

A. To be diagnosed with autism, you must have:
  • At least SIX (6) of the below symptoms from categories (1), (2) and (3)
  • You must have TWO (2) symptoms from (1- Social)
  • And ONE (1) each from (2- Communication) and (3- Behaviors and Interests)
  • The other one (or more) can be from any of the categories


Social interaction is impaired; must have TWO from list of symptoms below:

(a) Problems with nonverbal behaviors such as eye contact, facial expression, body postures and gestures used in social situations

  • Body Postures – may hold arms close to sides, may try to avoid certain types of social contact, may appear unapproachable due to posture
  • Eye contact – different from peers, may only meet eye-gaze of certain people or have total lack of eye contact – or anything in between
  • Facial expression – may seem inappropriate to what the situation warrants, may have blank gaze, may not greet you with a smile, may have same expression on face most of time – or any combination thereof
  • Gestures – may not respond to a hand held out to shake hands, arms out for hugs etc. May not understand social ‘cues’ we take for granted

(b) Does not make friends like other children in same age group

  • Children learn to play by imitation; this child is not imitating the other kids
  • May approach peers, but not to play…watch and see if the child is approaching in the same way peers approach each other
  • Seems to have no interesting in socializing with peers
  • While peers are learning to play together, the child is off by themselves

(c) Does not share objects with others for enjoyment

  • Does not bring you something that interests them to share with you
  • Does not point in the distance (i.e., to an airplane) to share with you something that interests them
  • Look at peers and how they show things they are proud of (e.g., artwork) and see if child does the same thing

(d) Lack of social (consisting in dealings or communications with others) and emotional (characterized by emotion) ‘give and take’; does not respond to social or emotional cues

  • Does not attempt to comfort someone who is crying
  • Does not become grateful or excited in anticipation of outing or gift (in the same way a peer would)
  • Does not reply “hello” to your greeting (without prompting)
  • Does not seem especially happy to see you when you return home after work
  • Does not seem to pick up on the ‘vibes’ of others
  • Does not seem to seek out or enjoy the company of others; may be aloof
  • Does not smile back when you smile at him/her (without prompting)


Communication difficulties; must have at least ONE of the below symptoms:

(a) Delay in, or total lack of, speech, but does not use gestures to communicate (delay = not at same level as peers)

  • Does not ‘mime’ his/her needs (i.e., Mime ‘eating’ if hungry)
  • Does not point to what s/he wants
  • Does not shake or nod head for ‘no’ or ‘yes’
  • Does not shrug shoulders to show s/he ‘doesn’t know’

(b) If child can speak, cannot start or hold up their end of a conversation (appropriately)

(c) May echo phrases, words, songs, parts of movies etc.

(d) Does not engage in imaginative play (as peers)

  • Will not make dolls ‘talk’ to each other
  • Will not pretend to brush doll’s hair
  • Will not pretend to drink from toy teacup
  • Will not take a toy airplane and ‘fly’ it around the room while saying ‘zoom’
  • Will not use items for make belief (i.e. a stick for a cane or a magic wand)


Repetitive behaviors, interests, and activities – child may get angry if this ‘pattern’ is interrupted; must have at least ONE of the below symptoms:

(a) Child is so focused on an interest that to remove the interest will result in a meltdown

(b) Routines or rituals must be followed; they appear to have no function

  • Family members must always sit in same seats; failure may result in tantrum
  • If you go to the video store, you must rent “The Smurfs” every time or risk a tantrum
  • Lining up cars is not necessarily playing ‘garage’; if you attempt to join in, the child will tantrum, walk away, push you aside, etc.
  • Must take same route home; one deviation may cause meltdown
  • Must wear red shirt on Tuesday or risk a tantrum etc

(c) Repetitive behavior such as hand flapping, rocking, ear flicking, chewing on clothing, vocal ‘stims’, spinning etc. (establish if this is self-stimulatory by doing a functional assessment)

(d) Preoccupied with parts of objects

  • Cover parts of book so that s/he can look at one piece
  • Focus on one part of a toy (i.e. doll’s eyes)
  • Spins wheels of toy cars

B. Child is either delayed (not same ‘age’ as peers) or acts differently from peers in ONE of the following (must be noticeable before age three): (1) social interaction, (2) language as used in social communication, or (3) pretend play

C. Child does NOT have Rett’s or Childhood Disintegrative Disorder

Treatment for autism is a very intensive, comprehensive undertaking that involves the youngster's entire family and a team of professionals. Some programs may take place in the home with professionals and trained therapists and may include Parent Training for the youngster under supervision of a professional. Some programs are delivered in a specialized center, classroom or preschool. Families usually decide on one plan of intervention that works best for them. Typical types of intervention are Applied behavior analysis (ABA), Pivotal response therapy (PRT), The P.L.A.Y. Project, Verbal Therapy, Floortime, Relationship Development Intervention (RDI), and The Son-Rise Program.

Next we will look at PDD-NOS…

PDD-NOS is a diagnosis by exclusion. If a child presents with some symptoms from (1), (2), and/or (3) above, and their pattern of symptoms is not better described by one of the other PDD diagnoses (i.e., Autism, Aspergers, Rett’s, or Childhood Disintegrative disorder) then a professional might decide that a diagnoses of PDD-NOS is warranted.

When comparing PDD-NOS to Autism, PDD-NOS is used when a child has symptoms of autism as above, but not in the configuration needed for an autism diagnosis. Social component is where the most impairment is seen. Children who fail to meet criteria for autism and don’t have adequate social impairment typically have a developmental disability, and their symptoms can be accounted for by that.

Looking at above description:

“299.00 Autism - To be diagnosed with autism, you must have at least 6 of the below symptoms from (1), (2) and (3). You must have two symptoms from (1) and one each from (2) and (3) – the other two can be any of the other symptoms.”

PDD-NOS is most often diagnosed when children have significant social impairments, but don’t have the symptoms in area (3). A child with PDD-NOS may have the same (or more, or less) number of symptoms as a child with autism, but instead of having 2 from #1 and one each from #2, the child might have 1 symptom from #1 and one from #2, plus two from #3.

PDD-NOS is typically diagnosed by psychologists and Pediatric Neurologists. No singular specific test can be administered to determine whether or not a youngster is on the spectrum. Diagnosis is made through observations, questionnaires, and tests. A mother or father will usually initiate the quest into the diagnosis with questions for their youngster's doctor about their youngster's development after noticing abnormalities. From there, doctors will ask questions to gauge the youngster’s development in comparison to age-appropriate milestones. One test that measures this is the Modified Checklist of Autism in Toddlers (MCHAT). This is a list of questions whose answers will determine whether or not the youngster should be referred to a specialist such as a Developmental pediatrician, a neurologist, a psychiatrist, or a psychologist.

Because PDD-NOS is a spectrum disorder, not every youngster shows the same signs. The two main characteristics of the disorder are difficulties with social interaction skills and communication. Signs are often visible in babies, but a diagnosis is usually not made until around age 4. Even though PDD-NOS is considered milder than typical autism, this is not always true. While some characteristics may be milder, others may be more severe.

Once a youngster with PDD-NOS enters school, he will often be very eager to interact with classmates, but may act socially different than peers and be unable to make genuine connections. As they age, the closest connection they make is typically with their mom and dad. Kids with PDD-NOS have difficulty reading facial expressions and relating to feelings of others. They do not know how to respond when someone is laughing or crying. Literal thinking is also characteristic of PDD-NOS. They are unable to understand figurative speech and sarcasm.

Inhibited communication skills are a sign of PDD-NOS that begins immediately after birth. As an infant, they will not babble, and as they age, they do not speak when age appropriate. Once verbal communication begins, their vocabulary is often limited. Some characteristics of language-based patterns are: repetitive or rigid language, narrow interests, uneven language development, and poor nonverbal communication. A very common characteristic of PDD-NOS is severe difficulty grasping the difference between pronouns, particularly between “you” and “me” when conversing. Difficulty with this would look something like this:

Parent: “Do you want to color this or do you want me to?”

Child: “Me.”

This “me” response would be because, since the mother or father spoke the word "me", the youngster thinks that "me" still applies to the parent. The youngster with autism cannot grasp - without intervention - that the pronoun assignment of “me” refers to the speaker, and not to whomever spoke it first.

A diagnosis of PDD-NOS is not necessarily a less-severe one than a diagnosis of autism, but can be sometimes. Severity of any spectrum disorder can be determined by the amount and severity of symptoms listed above.

It is imperative to obtain a thorough psychological assessment performed. If you do not understand during any part of the assessment, ask questions. You should feel comfortable to go home and ‘digest’ the information given to you, form any questions or concerns and contact the diagnosing clinician to get your answers.

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