Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS)

You may know someone who’s like this: looks really normal, but when speaking, sometimes, she doesn’t fully understand language, sometimes, she talks like a child or professor or philosopher. She has complete limbs but seem not to do tasks well. At far she stands good, but when near her, she has poor gait. She rather be alone than socialize, seems so shy. She is maybe very beautiful, but cannot groom herself, and has no experience in romance. You may suspect she has autism, but hey, she talks. Maybe she has ADHD, but not really. She has dyspraxia, but not clumsy enough. What does she have? These symptoms are part of the “atypical autism,” better known as pervasive developmental disorder-not otherwise specified (PDD-NOS).

What is PDD-NOS?

PDD-NOS is a sub-type of autism spectrum disorder (ASD) marked with autism symptoms but not fully to be diagnosed with typical autism. Generally, PDD-NOS is under the umbrella ASD or pervasive developmental disorders (PDD) where it is a group of conditions that involve delays in the development of many basic skills. Most notable among them are the ability to socialize with others, to communicate, and to use imagination (triad of impairments). Children with these conditions often are confused in their thinking and generally have problems understanding the world around them.[1]

PDD-NOS is a ‘subthreshold’ condition in which some – but not all – features of autism or another explicitly identified Pervasive Developmental Disorder are identified.[2] It is also referred to as “atypical personality development,” “atypical PDD,” or “atypical autism.”[2]

Like all forms of autism, PDD-NOS can occur in conjunction with a wide spectrum of intellectual ability. Its defining features are significant challenges in social and language development.[3]

Image courtesy of Dr. Joshi’s Center for Autism. PDD-NOS is under the ASDs which is under the broader PDDs.

PDD-NOS is removed from the current DSM-5 and is replaced by the general autism spectrum disorder by severity. But in ICD-10, PDD-NOS is still accepted

What causes PDD-NOS?

Like in other ASDs, PDD-NOS has no definitive cause, but PDD-NOS can run in families. The underlying basis of PDD is neurological and most probably genetic. They affect more boys than girls and are usually evident by age three years, although in the case of PDD-NOS the signs may not be noticed until slightly later.[4]

What are the symptoms of PDD-NOS?

PDD-NOS symptoms are the following[5]:

  • Do not respond to their name by 12 months of age.
  • Do not point at objects to show interest (point at an airplane flying over) by 14 months.
  • Do not play “pretend” games (pretend to “feed” a doll) by 18 months.
  • Avoid eye contact and want to be alone.
  • Have trouble understanding other people’s feelings or talking about their own feelings.
  • Have delayed speech and language skills.
  • Repeat words or phrases over and over (echolalia).
  • Give unrelated answers to questions.
  • Get upset by minor changes.
  • Have obsessive interests.
  • Flap their hands, rock their body, or spin in circles.
  • Have unusual reactions to the way things sound, smell, taste, look, or feel.

Generally, PDD-NOS symptoms are[6]:

  • Communication difficulties (e.g., using and understanding language)
  • Difficulty with social behavior
  • Difficulty with changes in routines or environments
  • Uneven skill development (strengths in some areas and delays in others)
  • Unusual play with toys and other objects
  • Repetitive body movements or behavior patterns

Studies suggest that persons with PDD-NOS belong to one of three very different subgroups[6][7]:

  • A high-functioning group (around 25 percent) whose symptoms largely overlap with that of Asperger syndrome, but who differ in terms of having a lag in language development and/or mild cognitive impairment.[7] (The criteria for Asperger syndrome excludes a speech delay or a cognitive impairment.[8])
  • A group (around 25 percent) whose symptoms more closely resemble those of autistic disorder, but do not fully meet all its diagnostic signs and symptoms.[7]
  • The biggest group (around 50 percent) consists of those who meet all the diagnostic criteria for autistic disorder, but whose stereotypical and repetitive behaviors are noticeably mild.[7]

How is PDD-NOS diagnosed?

To diagnose PDD-NOS, a child must have a certain number of characteristics relating to social and communication skills, and also show some repetitive behaviour. When a child has only some of these characteristics, the child might be diagnosed with pervasive developmental disorder – not otherwise specified (PDD–NOS).[9]

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.[10]

Although PDD-NOS is milder than the typical autism (autistic disorder), much difficulty in navigating the world is apparent when compared to a neurotypical (NT). The sad part is, PDD-NOS is harder to diagnose than autistic disorder because people with PDD-NOS can talk and usually have average to high intelligence (though can also exist in low intelligence), can be assimilated into school and/or work, and can live independently. The problem with PDD-NOS is that the child or adult with PDD-NOS is “labeled” as Different. Clearly. “Weird.”[11] They are also prone to be loners as well because of their inappropriate social behavior.

Image courtesy of People with PDD-NOS are usually described as loners.

To better understand PDD-NOS symptoms, let’s quote from My Asperger’s Child about PDD-NOS[10]:

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.

The former DSM-IV diagnostic criteria of PDD-NOS go like this[12]:

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 happens if PDD-NOS is not diagnosed?

PDD-NOS is more than just a combination of language disorders, motor disorders, and social difficulties. This is an autism spectrum disorder with atypical or uneven development: can talk but cannot comprehend language, can move limbs but cannot play sports or dance, can make acquaintances but cannot form close friends and romantic relationships, can go to school and learn but cannot work and be employed long-term, and this makes one of the most difficult neurodiverse conditions to be identified, making people with PDD-NOS very prone to social isolation, unemployment, homelessness, depression, anxiety, OCDs, various mental disorders, and suicide. That’s why the earlier the identification and intervention for PDD-NOS, the better the outcome.

How is PDD-NOS managed?

PDD-NOS has no cure. To achieve the best possible progress children identified with PDD–NOS need focused support and intervention early on. And, the intervention programme must be tailored to suit the child’s specific needs.[13]

Interventions include[13]:

  • Special Education – this is the concept of tailoring or adapting day to day education to specifically meet a child’s unique learning needs. This may include modified curriculum and modified reporting systems. It is obligatory in most developed countries.
  • Establish an Individualised Educational Plan (IEP) or a Negotiated Educational Plan (NEP) – this is a plan formulated by school staff, specialists and parent input. This plan lays the groundwork for necessary therapies and academic training. IEP’s and NEP’s can be developed as funded or unfunded options.
  • Behavior Modification – the development of positive strategies to support the behaviour of the child to improve their learning and functioning (Applied Behavior Analysis makes use of reinforcements so that the child learns to respond in a particular manner. It rewards positive behaviours and ignores the undesirable ones. The desired outcomes are broken down into attainable, success-based tasks. This teaches the child how to learn so that they can then move on to academic work)
  • Teaching and learning – quite often, these children simply require a little more time to learn and respond. Their learning is always buoyed by additional visual input. Never underestimate the positive impact on learning when a student and teacher (and parents) have the best of relationship.
  • Develop visual aids; schedules, planners and timetables – these children often resist change to their routines. It is important to provide them with a plan so they know what activities are first, next, and last. If they are unable to read, then use picture cues on the schedule. These kids are reliant on advanced notice of imminent changes.
  • Speech Therapy – this specialisedadditional work is often needed to correct specific letter and word pronunciations. When necessary, language skills are addressed to help the child learn how to respond appropriately to certain phrases and questions. This type of therapy is often administered on an individualised basis, by a speech therapist. It is very appropriate for therapy to occur during the course of the school day.
  • Occupational Therapy – offers designs to increase the child’s day to day and classroom functional abilities (sensory integration therapy). Sensory problems often cause children to be overly sensitive to textures, noises, smells and sounds. If the child has problems with fine motor skills that hinder writing and other class tasks, therapy can be used to address these problems as well. Again, it is very appropriate for therapy to occur during the course of the school day.
  • Medication – considered to treat specific secondary symptoms such as anxiety, depression, hyperactivity and highly aggressive or reactive behaviours
  • Social Skills Training – where children are explicitly taught pro-social behaviours; how to interact with their peers in specific situations[13]
  • Complementary Therapies – martial arts, gymnastics and music therapy, assist children flex their muscles, literally and figuratively, as they learn how to function in a group setting away from school[13]

Some of the more common therapies and services include:[6]

Image courtesy of Therapy, Learning & Communication – WA. The earlier the intervention for PDD-NOS, the better the outcome.

Adults with PDD-NOS? What to do?

If an adult suspects he might have PDD-NOS, usually a referral to a psychiatrist is first made. This is usually because he has experienced struggles with the so-called “triad of impairments” – socialization, communication, and language (as opposed to speech) and is already suffering from depression or other mood disorder. Although adult diagnosis of PDD-NOS is difficult at first, still he must describe his symptoms suspected to be identifiable with PDD-NOS (cannot hold a regular job, longtime involuntary celibacy, depression, etc). Once a diagnosis is made, therapies to manage PDD-NOS for children are also applied to adults, as well as support groups are also included in management for PDD-NOS.

Adults with PDD are able to function at varying degrees depending on the severity of the disorder. Many adults with milder forms of PDD are able to work and live on their own or with some help. Still, difficulties communicating and relating to people can cause problems in many areas of life. People with PDD can benefit from skills training, support, and therapy into adulthood.[14]

Regardless, people with PDD-NOS are still people after all. ll they need is acceptance and support for them to live satisfying lives.


  7. Walker DR, Thompson A, Zwaigenbaum L, Goldberg J, Bryson SE, Mahoney WJ, Strawbridge CP, Szatmari P 2004. Specifying PDD-NOS: a comparison of PDD-NOS, Asperger syndrome, and autism. J Am Acad Child Adolesc Psychiatry. 2004 Feb;43(2):172-80. PMID 14726723 [1] and [2].
  8. American Psychiatric Association (2000).“Diagnostic criteria for 299.80 Asperger’s Disorder (AD)”. Diagnostic and Statistical Manual of Mental Disorders (4th, text revision (DSM-IV-TR) ed.).ISBN 0-89042-025-4. Retrieved 2007-06-28.

Further Reading:


4 thoughts on “Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS)

  1. Pingback: Asperger’s Syndrome vs Narcissistic Personality Disorder | Aegyo Kawaii's Neurodiversity Blog

  2. Pingback: Pragmatic Language Impairment | Aegyo Kawaii's Neurodiversity Blog

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s