※ [本文轉錄自 tmlu 信箱]
作者: tm@bbs.sob.com.tw
標題: ◇ [參考]Autism FAQ (6):Theories and Causes
時間: Mon Oct 14 21:53:12 2002
作者: Jf (寫給往事的一封匿名信) 看板: NTUStar_rain
標題: [參考]Autism FAQ (6):Theories and Causes
時間: Thu Sep 27 19:43:15 2001
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Autism FAQ - Theories and Causes
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There is no theory of the cause of autism which everyone has found
convincing. There may be multiple causes. Thus we will review some of
the proposed causes.
Most researchers are absolutely convinced that the cause is biological
rather than psychological. Bernard Rimland in his book Infantile
Autism (1965) cited the following evidence for a biological genesis
and against the idea that parents cause their children to be autistic:
1. Some clearly autistic children are born to parents who do not fit
the autistic parent personality pattern.
2. Parents who do fit the description of the supposedly pathogenic
parent almost invariably have normal, non-autistic children.
3. With very few exceptions, the siblings of autistic children are
normal.
4. Autistic children are behaviorally unusual "from the moment of
birth."
5. There is a consistent ratio of three or four boys to one girl.
6. Virtually all cases of twins reported in the literature have been
identical, with both twins afflicted.
7. Autism can occur or be closely simulated in children with known
organic brain damage.
8. The symptomatology is highly unique and specific.
9. There is an absence of gradations of infantile autism which would
create "blends" from normal to severely afflicted.
Points 4 and 9 are not generally accepted now, perhaps because of the
broadening of the condition's definition over time, and perhaps
because of additional observation & data collection.
There is still controversy over neurological differences in the brains
of autistic people and the rest of the population. However, it does
appear from evidence obtained through autopsies, MRI and PET scans
that there are subtle cellular changes in the autistic brain. The
increased incidence of seizures (20-30% develop seizures in
adolescence) also points to neurological differences.
Some specific theories as to the cause of autistic symptoms:
* Yeast infections.
* Intolerance to specific food substances. (see below)
* Gluten intolerance ("Leaky Gut Syndrome"/Casein intolerance
causing intestinal permeability and allowing improperly digested
peptides to enter the bloodstream and cross the blood-brain
barrier which may mimic neurotransmitters and result in the
scrambling of sensory input.
I've also heard "Leaky Gut Syndrome" described as lack of the
beneficial bacteria that aids digestion, and that the resulting
matter in the bloodstream invokes an unnecessary immune reaction.
* Phenolsulphertransferase (PST) deficiency--theory that some with
autism are low on sulphate or an enzyme that uses this, called
phenol-sulphotransferase-P. This means that they will be unable to
get rid of amines and phenolic compounds once they no longer have
any use for them. These then stay in their body and may cause
adverse effects, even in the brain. Treatment is dietary as well
as epsom salts baths.
* Brain injury.
* Constitutional vulnerability.
* Developmental aphasia.
* Deficits in the reticular activating system.
* An unfortunate interplay between psychogenic and
neurodevelopmental factors.
* Structural cerebellar changes.
* Genetic causes.
* Viral causes.
* Immunological ties.
* Vaccines.
* Seizures.
A phrase you will sometimes hear is "theory of mind" or "the theory of
mind hypothesis". This is not so much a supposed cause of autism as an
assertion as to its nature. The basic idea of the hypothesis is that
autistic people lack an awareness of other peoples' minds that typical
people start developing at a relatively young age, i.e. the autistic
person doesn't so readily develop theories about what is going on in
other people's minds. A corollary is that an autistic person's
awareness of other people's minds is something that is developed
intellectually through their own efforts. Furthermore, adherents of
this theory suppose that some or all the other typical characteristics
of autism stem from this one main deficit. The hypothesis is explained
in some books (some have "Theory of Mind" in the title, also Uta Frith
has written on it) and simple tests have been devised to test a
person's awareness of other minds.
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