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 PDD-NOS and McDD in the DSM
A critical article, made in the DSM-III, about the choices concerning autism and the autism related disorders (written by employees of Yale Child Study Center in 1986) and supported by later studies (Siegel 1986, Dahl, Cohen en Provence 1986, Szatmari 1992), has caused, based on solid pre-investigation (1994), that a number of subcategories are included in the DSM-IV (Asperger's syndrome, Rett's syndrome and the desintegrative disorders).
(more in the link above)
They assumed that within the restgroup PDD-NOS, a few subcategories of persons, showing characteristics related to autism (disorder in the reciprocal social relations) but differing from autistic people on other details, would be identified.

Cohen and employees (1986) asked for attention about a proposal that got no hearing.
It was about a group of children that regularly were seen in clinical practice, but in literature named very differently so far viz.:
  • atypical development
  • symbiotic psychosis
  • borderline disorders in childhood
  • schizoid personality disorders on childhood
  • schizotypical disorders
On ground of literature investigation they came up with the idea that all those children match the criteria summarised in three main categories:

   1. disorders in the sensitivity for social signals and in the development of reciprocal social relations.
   2. disorders in the regulation of affects.
   3. disorders in thinking.

The syndrome manifests itself on the age of 2-3.
There are no indications for an autistic or schizophrenic disorder.

First this concept got the name Multiplex Developmental Disorder, but changed its name in 1993 to Multiple-complex Developmental Disorder, because the initial abbreviation MDD caused too much confusion with the more naturalised abbreviation for 'Major Depressive Disorder'. The new abbreviation matches no predecessor.
The name itself doesn't say anything more about this group than that the development is disturbed on more levels.

McDD is a developmental disorder considered to be a sub-type of PDD-NOS, the restgroup of pervasive developmental disorders, and is therefore a related disorder of autism.
(more information about McDD, you can find in the link above)
Mostly it will be diagnosed as such, because it isn't mentioned in the DSM-IV-TR yet.

It would be better though that autism related disorders aren't seen as a milder form of autism. Several symptomatological factor analyses have revealed that the autism spectrum can be divided in four groups:
  • the classical Kanner-type autistic patients
  • a group of Kanner-type autistic patients with mental retardation
  • a group of atypical patients with more organic disturbances
  • a group of patients with more affective and schizoid symptoms can be distinguished (Dahl et al, 1986; Siegel et al, 1986; Szatmari et al, 1989) and these matches the group of multiple-complex developmental disorders (Cohen et al, 1986).
Because of the lack of clear diagnostic criteria, the investigation on this last mentioned group is hampered, which is regretable, especially because autism related disorders are more common than autism itself.
© 2006 #McDD - realisation: E. Appermont