Posted by

[Fred A. Baughman Jr., MD:
The fundamental problem with this research, as with all biological
research in psychiatry is that no one of these 3 entities– (1) dyslexia,
(2) dyspraxia or (3) adhd is a diagnosable entity, disease, having a
confirming, objective, demonstrable diagnosable physical or chemical
abnormality. This being the case there is no physical or chemical
abnormality (marker) to set the subject/patient with 1, 2, or 3 apart
from normal, control subjects. This being the case, research on 1, 2, or
3 is doomed to prove nothing. In most psychiatric research the only
physical difference in subjects/persons having 1, 2, or 3 are those
induced by the drugs they are being or have been treated with. Here we
see other disciplines, in this case ‘neuroscience’ also, MRI or
‘neuroimaging’ lending credence to such disease and syndrome
designations and thus to all research and practice and treatment where
they are concerned.


Alexandra J. Richardson

Senior Research Fellow in Neuroscience, Imperial College School of
MRI Unit, Hammersmith Hospital, London; and University Lab. of
Physiology, Oxford.


There is a wide spectrum of conditions in which deficiencies of highly
unsaturated fatty acids (HUFA) appear to play a role (Glen et al, 1999).
This includes atopic (allergic) conditions such as eczema and asthma as
well as psychiatric disorders such as schizophrenia and depression. The
focus here is on the role of HUFA in three common learning and
behavioural disorders - dyslexia, dyspraxia and attention-deficit /
hyperactivity disorder (ADHD), although similar issues may also be
relevant to the autistic spectrum (Richardson and Ross, 2000).

Dyslexia alone affects at least 5% of the general population in a severe
form, as does ADHD, although estimates rise when milder forms are
included. Dyspraxia remains less well-known, but prevalence appears to
be similar. There is considerable overlap between dyslexia, dyspraxia
and ADHD and each can occur with differing degrees of severity. Current
evidence suggests that up to 20% of the population may be affected to at
least some degree by one or more of these conditions. The associated
difficulties usually persist into adulthood, causing serious problems
not only for those affected, but also for society as a whole.


The clinical overlap between these conditions is substantial: each can
appear in isolation, but very often the same individual will show
features of two, or even all three, of these disorders. Unfortunately,
there is usually no such overlap in diagnosis and management. Official
diagnosis of ADHD lies in the realm of psychiatry, with stimulant
medication as the most likely treatment. Dyslexia is usually seen as an
educational or psychological problem, and management is usually by these
methods. Dyspraxia is the least recognised of the three, and if it is
diagnosed at all, referral will often be to a physiotherapist or
occupational therapist.


The defining feature here is specific problems in learning to read and
write in relation to general ability or IQ, but problems with arithmetic
and reading musical notation are also common. Poor working memory -
especially for sequenced, auditory-linguistic material - is a central
characteristic, and difficulties with phonology (the sounds in words)
are often regarded as a core feature, although these are typically found
in any poor readers. Associated features include problems in
distinguishing left and right, poor direction sense, difficulties with
time and tense, and subtle problems with both visual and auditory
perception. The overlap with ADHD is around 30-50%, and with dyspraxia
it may be even higher.

There is a clear biological basis to dyslexia. Genetic studies suggest
heritability of around 50%, prevalence across cultures is similar (and
independent of socio-economic status and IQ), and more males than
females are affected. Differences in brain structure in dyslexia include
an unusual symmetry of language areas and microscopic differences in the
arrangement and connection of neurons. The visual and auditory problems
point to a mild disorder of ‘magnocellular’ systems, specialised for
very rapid information processing.


Core problems involve difficulties in planning and carrying out complex,
sequenced actions.  In motor co-ordination, this shows in clumsiness,
difficulties with catching a ball or balancing, tying shoelaces or doing
up buttons. However, dyspraxic children often have extremely poor
handwriting, if not the other features of dyslexia, and difficulties
with organisation, attention and concentration, as in ADHD, are very
common. Dyspraxia is also associated with poor memory for symbolic
material, both visual and auditory, and often with impulsivity and
temper tantrums. These children can be hypersensitive to touch, smells
and sounds, and they often prefer repetitive, familiar activities
because they can find novel situations very stressful.


The central problems here involve Inattention, i.e. persistent
difficulties with sustained attention and concentration, and/or
Hyperactivity-Impulsivity. Hyperactive-Impulsive children show excessive
motor activity and restlessness, an inability to regulate behaviour
according to the situation, and difficulty delaying gratification.
Attentional problems are not always so obvious unless they occur
together with hyperactivity, but these alone can create equally serious
problems of under-achievement. A large proportion of ADHD children
(around 50%) also show clinical features of dyslexia and/or dyspraxia,
as noted above, although these associations are stronger for the
Inattentive form of ADHD than for Hyperactivity-Impulsivity.

Leave a Reply

  • (will not be published)