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For current information about PDD-NOS please see Autistic spectrum

Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS) is a pervasive developmental disorder diagnosis for people with most, but not all, of the characteristics of autism under the DSM-IV. PDD-NOS is also known as atypical personality development, atypical PDD, or atypical autism is absent. Usually, the issues focus more on social interaction.

Yale University describes PDD-NOS in these words: "Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS) is a 'subthreshold' condition in which some - but not all - features of autism or another explicitly identified Pervasive Developmental Disorder are identified. PDD-NOS is often incorrectly referred to as simply "PDD." The term PDD refers to the class of conditions to which autism belongs. PDD is NOT itself a diagnosis, while PDD-NOS IS a diagnosis. The term Pervasive Developmental Disorder - Not Otherwise Specified ... encompass cases where there is marked impairment of social interaction, communication, and/or stereotyped behavior patterns or interest, but when full features for autism or another explicitly defined PDD are not met."[1] In 2013 the DSM-5 combined PDD-NOS with other similar conditions to form the Autistic spectrum.

Signs & symptoms[]

There is no set pattern of symptoms and signs in children with PDDNOS. It is important to realize that a very wide range of diversity is seen in children with PDDNOS. All signs and symptoms / behavior patterns are common in these children, but a single child seldom shows all the features at one time. In other words, all children with PDD-NOS do not have the same degree or intensity of the disorder. PDD-NOS can be mild, with the child exhibiting a few symptoms while in the school or neighborhood environment. Other children may have a more severe form of PDD-NOS and have difficulties in all areas of their lives. Because of the possibility that PDD-NOS and Autistic Disorder are on a continuum, many clinical features observed in children with PDD-NOS are very similar to those being described in the literature for Autistic Disorder. Major signs and symptoms of PDD-NOS are described below[2]:

  • Deficits in social behavior:
  • Impairment in nonverbal communication: Some of the impairments in nonverbal communication accompanying PDD-NOS are:
  1. These children don't copy their parents to the extent the children without PDD-NOS.
  2. They do a number of activities without any accompanying facial expressions. For instance, they may develop the gesture of pulling adults or parents but without any expression on the face.
  3. They generally don't participate in games and activities that require imitation.
  4. With growing years when the children are in middle and late childhood, they are able to understand other people's gestures though they themselves don't use gestures.
  5. The children with PDD-NOS "are able to show joy, fear, or anger, but they may only show the extreme of emotions." However, no facial expressions accompany these emotions.
  • Impairment in understanding speech: Impairments in understanding speech by children with PDD-NOS has some of the characteristics like:
  1. Children or persons with PDD-NOS having mental retardation may not be able to ever develop the ability of speech.
  2. Children with a less severe PDD-NOS may be able to follow simple speech if accompanied by suitable gestures. For example, telling someone to bring the newspaper while pointing to the newspaper may be understood by such children.
  3. Mostly, the affected children fail to understand and comprehend the real meaning of humor or sarcasm or common sayings, etc.
  • Impairment in speech development:
  • Unusual patterns of behavior: Unusual pattern of behavior include the following:
  1. Resistance to change: The affected child feels highly distressed at the slightest change. For instance, minor changes in regular routines may lead to tantrums or the child becomes very sad if lines of toys or objects created by them is disturbed.
  2. Ritualistic or compulsive behaviors: These behaviors involve rigid routines like insistence on having same foods, or repetitive acts like hand flapping. Some children become obsessed with certain tasks, like memorizing weather data, state capitals, etc.
  3. Abnormal attachments and behaviors: Sometimes, some children may develop attachments to odd objects like batteries or pipe cleaners. Some children may develop infatuation with features like texture or the color of certain articles of their choice.
  4. Unusual responses to sensory experiences: Many children with PDD-NOS may "seem underresponsive or overresponsive to sensory stimuli." Thus, they may be mistaken to be deaf or dumb at times. Some of them may act in a different way - liking the rough touch to gentle caressing or selecting foods in a very restrictive way or taking foods from a wide variety.
  • Disturbance of movement: The motor skills of the affected children may be delayed but are generally within the acceptable normal ranges. They may be overactive at younger ages and may become less overactive in adolescence. They may "exhibit characteristics such as grimacing, hand flapping or twisting, toe walking, lunging, jumping, darting or pacing, body rocking and swaying, or head rolling or banging." Sometimes, such activities appear occasionally while in some cases, they are being exhibited over a period of time.
  • Intelligence and Cognitive Deficits:
  • Associated features: Some children affected with PDD-NOS may have the emotional expression that may be "flattened, excessive, or inappropriate to the situation." For instance, they may scream or cry without any reason while at times they may giggle or laugh hysterically. Sometimes, they may ignore the real dangers like moving vehicles or the possibility of falling from heights, while may get scared of harmless object like a particular stuffed animal.


The causes of PDD identified by the Center for Children with Disabilities [1] has been indicated in these words: "Both behavioral and biological studies have generated sufficient evidence to suggest that PDDNOS is caused by a neurological abnormality - problems with the nervous system. However, no specific cause or causes have been identified. While studies have found various nervous-system problems, no single problem has been consistently found, and exact causes are far from clear. This may be due to the current approach of defining PDD-NOS based on behaviors (as opposed to, say, genetic testing). Hence, it is possible that PDD-NOS is the result of several different conditions."


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