Dyslexia, dyspraxia, dyscalculia, ADD, ADHD and autism are considered as being separate disorders still. However there is more and more evidence to suggest that, on the basis of co-morbidity, they should be considered the symptoms that appear in syndromes of developmental delay or a special way of information processing, and can be called “atypical development”.

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Éva Gyarmathy
Atypical development – theory
Dyslexia, dyspraxia, dyscalculia, ADD, ADHD and autism are considered as being separate
disorders still. However there is more and more evidence to suggest that, on the basis of co-
morbidity, they should be considered the symptoms that appear in syndromes of
developmental delay or a special way of information processing, and can be called “atypical
development”.
Studies, based on children with dyslexia revealed the large frequency of co-morbidity to
many neurologically based disorders, like different specific learning difficulties, ADD, ADHD
and autism. There are many common features that indicate the connection.
All of these specialties are neurologically based, usually identified early in children’s nursery
or primary education. However the mild versions are not easy to identify, and many times
the diagnosis may be false or because of the overlapping symptoms the syndromes are
mixed up. All these specialties are irrespective of individuals level of intelligence and
motivation, however the early intervention and the environment can be crucial in the
appearance of these specialties. Tremendous research data prove the co-morbidity, and that
a child may often exhibit more than one of these complex syndromes.
Evidences for fatty acid abnormalities in these disorders have been found as background
factor of the high degree of co-morbidity (Richardson, Ross, 2000)
Research evidence suggests that motor planning and sequencing, rhythm and timing are
relevant to ADHD and dyslexia as well as to autism spectrum disorders. Deficits in inhibition
and executive functions, which involve the regulation and sequencing are important part of
the ADHD. Several data shows relationship between attention, motor regulation, inhibition,
speed, rhythm and coordination (Schonfeld, et al, 1989; Barkley, et al, 1997; Piek et al,
1999). Similar results are proved at dyslexic children (Denckla, et al, 1985) and children with
autism (Greenspan, Wieder, 1999).
Dyslexia is often associated with deficits in related domains such as language acquisition
diagnosed as dysphasia, dysgraphia and misspelling, dyscalculia, motor coordination as a
leading symptom in dyspraxia, postural stability and dexterity, temporal orientation, visuo-
spatial abilities in developmental right-hemisphere syndrome, and attention in ADD and
ADHD (Habib, 2000).
Dyscalculia and dyslexia have been shown to be combined with attention-deficit
hyperactivity disorder at a rate of 26% and 33%. In addition, 17% of children with dyscalculia
also showed considerable deficits in reading (Gross-Tsur, Manor, Shalev, 1996; Mayes,
Calhoun, 2006; Shaywitz, Shaywitz, 1988).
Executive functions (EF) are a set of high cognitive abilities that control and regulate other
functions and behaviors (Welsh et al., 1991). A variety of executive functions deficits have
been found in dyslexia (Reiter, et al 2005), in ADHD (e.g. Sergeant , et al, 2002) and in autism
(e.g. Hill, 2004; Hughes et al, 1994).
Pauc (2005) reported that the patterns of co-morbidity occurred with such frequency that
there could be an argument for the downgrading of these conditions from disorders per se

2. Unpublished research gyarmathy.eva@gmail.com OTKA 2017
to symptoms and the patterns of co-morbidity may fit the criteria for a developmental delay
syndrome.
Robert Melillo (2009) called these children the „Disconnected Kids”. He theorized that the
brain imbalance of these children was rather global, involving the anatomy and physiology of
the two hemispheres caused by the uneven development of the two hemispheres leading to
unsynchronized functioning. Reduced synchronized activity between the two hemispheres is
then said to materialize into one of the disorders.
The co-occurrence of these specialties may be caused by overlapping developmental
pathways and interacting genetic and environmental influences that we call now atypical
development.
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