Pervasive Developmental Disorder Not Otherwise Specified: what’s in a name?


The condition behind the unwieldy name

A dad once observed that his son didn’t have autism but PDDNOS: Pervasive Developmental Disorder Not Otherwise Specified. “I just wish he had something I could pronounce” he added wryly, “something someone has heard of”. Such exasperation is understandable given the somewhat cumbersome and commonly misunderstood acronym, PDDNOS, which describes a specific pervasive developmental disorder.

The term pervasive developmental disorders (PDD) first appeared in diagnostic manuals in the 1980s to define disorders with core characteristics overlapping with those described by Lorna Wing and Judith Gould as the “Triad of Impairments”: namely, those affecting social interaction, social communication and social imagination. This “triad” is often accompanied by a restricted and repetitive repertoire of behaviours.

Pervasive Development Disorder Not Otherwise Specified (PDDNOS), also sometimes incorrectly referred to as atypical autism, is one of a number of PDD, along with autism, Asperger’s syndrome, Rett’s syndrome, and childhood disintegrative disorder. Erroneously, PDDNOS is often shortened to PDD (the umbrella category under which PDDNOS is found). At present, the diagnostic criteria for all such disorders are under review as there is a need for greater clarity.

A child may be diagnosed with PDDNOS if he or she shows some behavioural features of autistic disorder but does not meet the full criteria. All of the listed PDD are part of a spectrum of overlapping conditions. To illustrate this, a child may begin with a diagnosis of PDDNOS, develop more autistic features with age, and be re-diagnosed with autism or another pervasive development disorder; conversely, a child with autism may improve and be re-diagnosed with PDDNOS.

PDDNOS is therefore a diagnostic category in its own right: a distinct developmental disorder. It is different from the, so called, “broader autism phenotype”: a term used to describe individuals who exhibit differences with personality, language and social behaviour at a higher than average level but lower than that required to meet the diagnostic criteria for PDD.

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 PDDNOS the signs may not be noticed until slightly later.

Diagnosis of PDDNOS relates to the child’s “instinctive” social behaviours. It requires demonstrable impairments in reciprocal social interaction, impairments in verbal and non-verbal communication, and the presence of unusual repetitive behaviour, interests and activities, but falling below the threshold for diagnosis of other PDD. This is evident through impaired communication and language development, play and interaction with other children, and their ability to relate to others, even their own family.

At school the child with PDDNOS may appear defiant, disobedient or lacking in interest: not responding to their name, seeming distant and being unable to show emotion except under extreme conditions such as fear. The child may eventually develop emotional ties with those closest to them but not others, whom they may seek to avoid. Because they struggle with peer relationships, they may find groups difficult and prefer more solitary activities. Reading between the lines of social encounters is problematic for them, and they may struggle to decipher facial expression or tone of voice unless these are obvious. They may be clumsy, and dislike team games or those involving throwing and catching. Their early hyperactivity commonly gives way in teenage years to lethargy. Such children may also be vulnerable to bullying and teasing as their unusual demeanour sets them apart from their peers.

For children diagnosed with autism, Rett’s or Asperger’s syndrome, such a diagnosis usually clears a path to information and support, but this may not be the case with PDDNOS. Additionally, there may be other medical and psychological conditions that complicate the clinical picture. These may include tics or seizure type disorders, dyslexia, ADHD, psychiatric disorders and some forms of conduct disorder.

What, then, is the difference between the needs of these children and those of children with autism or Asperger’s syndrome? In practical terms the answer is probably none. They will all respond to broadly similar approaches.

So what can we do to help? Whatever the label, a child with any form of PDD is a child first, with unique characteristics, requiring an individualised and informed approach. We must listen to the child and parents and spend time getting to know them. The school should become a trusted ally – not part of the problem. Children with these common but little known disorders may have perpetual anxiety, which can impact on the whole family. They need our support, friendship and practical help; the latter can be made available through statutory processes such as the Statement of Special Educational Needs or similar mechanisms, or through parental negotiation. These may be supplemented by a range of specialist professionals, for example occupational therapists and speech and language therapists, and in adolescence through personal mentors. Where there is a lack of certainty over diagnosis, the advice of a clinician, experienced in the diagnosis and treatment of such conditions, should always be sought.

If schools are to be inclusive and welcoming, reasonable adjustments should be made to the delivery of the curriculum, the school environment and processes. A recent study by David Skuse at the Institute of Child Health suggests that elevated autistic traits are much more common in the general population than previously thought. This has implications for schools as there are likely to be many more children who would thrive, and far fewer fail, if schools were friendlier places for them.

An “autism friendly” school is a place where stress is reduced through the security of structure and predictability, where the individual’s strengths and interests are used as a catalyst for learning; where self esteem is encouraged through reduced confrontation and the promotion of good health and a positive outlook; where harmful sensory stressors and other distractions are minimised, and where there is protection, fairness and an ethos of working closely with families. An “autism friendly” school is friendly to all.

In conclusion, there is no doubt that children with PDDNOS have a unique but poorly understood disorder that will make their lives challenging, especially during their school years. I would urge readers to find out more about the condition as a greater understanding can make an enormous difference both to outcome and the quality of life of the child and the family.

So what’s in a name?  As with other diagnostic labels, the rather ugly acronym PDDNOS will be useful only if it results in understanding, tolerance and help.

Further information

Richard Mills is Director of Research at The National Autistic Society and Hon. Sec. Research Autism:

Article first published in SEN Magazine issue 41: July/August 2009.

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