Causes of autism

The causes and etiology of autism are areas of				accompany autism in those who are non-mentally
debate and controversy; there is currently no				retarded, but the reasons for this and its effects
consensus, and researchers are studying a wide				are still unknown.
range of possible genetic and environmental				Research has not yet established exactly what is
causes. Since the way autism manifests is				specific to autism and what may be seen in other
different for each person, there are likely multiple				disorders however.
"causes" that interact with each other in subtle				Individuals with autism are also far more likely to
and complex ways, and thus give slightly differing				develop epilepsy than would otherwise be
outcomes in each individual. Two environmental				expected (estimated 10-30% incidence).
theories include the impact of vaccines on the				Genetic component
immune system (of which a statistically significant				Genetic influence comprises a significant aspect of
link has never been found despite many				research in the causes of autism. A large
attempts; see the vaccine theory for a more				database showing theoretical links between autism
extensive treatment) and a more recent theory				and genetic loci summarises research indicating
relating autism to high levels of television viewing				that the genetic influence may extend to every
while young. A correlation has also been found				human chromosome. It has been observed in one
between autism and the mercury emitted from				twin-study in Britain that there was about a 60%
coal power plants, though the implications of this				concordance rate for autism in monozygotic
correlation is uncertain. Mercury measurements of				(identical) twins, while dizygotic (non-identical) twins
hair samples from autistic children's first haircuts				and other siblings comparatively exhibited about
were significantly lower than a matched group of				4% concordance rates. Some research posits
normal children, declining as measures of severity				that the chances that an identical twin of an
increased.				autistic person will also be autistic are 85-90%.
Research claims also link autism with abnormal				The increased probabilities of siblings having autism
blood vessel function, and oxidative stress. This				has been calculated at about 35-fold more than
line of research may lead to new medical				normal.
therapies.				Accompanying impairments are also a common
Physiology and neurology				feature of autism. Some people with autism also
Autism appears to involve a greater amount of				have gastrointestinal, immunological or neurological
the brain than previously thought. A study of 112				symptoms in addition to behavioral impairments.
children (56 with autism and 56 without), published				These associated complexes have also lead to
in the Journal of Child Neuropsychology, found				the search for specific genetic connections and
those with autism to have more problems with				helped to focus on reasonable genetic implications.
complex tasks, such as tying their shoelaces or				Since genes provide the information for
writing, which suggests that many areas of the				processes and structure at the level of the cell
brain are involved. Children with autism performed				and its components during the growth and
simple tasks as well as or better than those				development of a human as well as maintenance
without. In tests of visual and spatial skills, autistic				during life, gene mutations (altered versions) and
children did well at finding small objects in complex				deletions (complete absence of genetic material)
pictures (e.g., finding the character Waldo in				and possibly extra copies of genes would mean
"Where's Waldo" pictures). However, they found it				that the causes of autism begin very early. If a
difficult to tell the difference between				mutated gene fails to perform properly, then cells,
similar-looking people. Children with autism tended				proteins, enzymes and other crucial aspects of
to do well in spelling and grammar, but found it				normal function may be significantly altered and
much more difficult to understand complex				operate incorrectly. Deletions could mean the
speech, such as idioms or similes when the				complete absence of a sequence of events due
meaning of the phrase is figurative. They would,				to missing proteins or cell components for
for example, not understand that "He kicked the				example. These genetic alterations and deletions
bucket" meant someone had died, or were likely				will simply bring about a changed structure or
to actually hop if told to "hop to it".				process which effects a great many other
The inference from this research, according to				needed structures and processes.
researchers at the Pittsburgh School of Medicine,				Another important aspect of research in genetic
is that "These findings show that you cannot				factors is environmental effects and the incidence
compartmentalize autism. It's much more				of autism. During the lifetime of a person, gene
complex.â€				mutations and deletions may be environmentally
The research from this perspective has a number				triggered or exacerbated. Conversely, it may also
of implications:				be that environment will not be a factor and
Autism is more than likely a global disorder which				nothing will change the autism characteristics. For
affects how the brain processes the information it				autism, the answer to these possible explanations
receives, while complex information tends to				is still being researched and there is evidence that
make this more readily apparent.				both may be true simply because there is more
Neurological â€˜wiringâ€™ in people				than one way a person may develop autism.
with autism manifest abnormalities in the areas of				Deletions and Mutations
the brain that communicate with each other.				Deleted genes have been noted as a probable
Observed abnormalities provide a reasonable				influence or cause in autism. By locating specific
explanation for why children with autism have				missing genetic material the significance may be
problems with complex tasks which require				that specific genetic sites for autism controlling or
multiple areas of the brain to work together;				causing autism (autism susceptibility alleles) may
autistic people tend to do better in tasks that only				be located precisely. Another significant aspect of
require one region of the brain.				this research is that these deletions of genetic
The causes of autism are possibly more				material indicate that autism may be established in
pervasive than previously believed; for example,				some cases during meiosis (error-prone meiosis
more areas of the brain are affected than just				model) and this places the genesis of autism in
those involving social interaction, communication,				some at the very beginning of life.
interests, and imagination.				One very important question in this line of
Autism may not be primarily a disorder of social				research is whether or not gene deletions are a
interaction; research must now take into account				cause or consequence of autism-susceptibility loci
non-social aspects.				located elsewhere in the chromosomes.
A possible explanation for the characteristics of				Gene mutations may mean a gene does not
the syndrome is a variation in the way the brain				function at all or does not function in the normal
itself reacts to sensory input and how parts of				way. Since genes direct how the body grows and
the brain then handle the information. An				develops, mutations, like deletions, will effect a
electroencephalographic (EEG) study of 36 adults				person at the most basic levels.
(half of whom had autism) at Washington				Mutation and deletion effects have been
University in St. Louis found that adults with				delineated in numerous research publications.
autism show differences in the manner in which				Correlated characteristics include global
neural activity is coordinated. The implication				developmental delay, mild to severe delay of
seems to be that there is poor internal				speech, social communication disorders and
communication between different areas of the				cognitive abilities, autistic like behaviour, high
brain. (Electroencephalographs, or EEGs, measure				tolerance of pain, and repetitive mannerisms (e.g.
the activity of brain cells.)				chewing or mouthing).
The study indicated that there were abnormal				Gene interaction may also complicate the causes
patterns in the way the brain cells were				leading to multiple genetic origins of autism, In a
connected in the temporal lobe of the brain. (The				cascade like effect, when a gene loci is altered or
temporal lobe deals with language.) These				omitted, others are effected due to change in
abnormal patterns would seem to indicate				interaction between genes and/or their functions.
inefficient and inconsistent communication inside				Though not present in all individuals with autism,
the brain of autistic people.				these mutations and deletions hold potential to
Studies in neuropathology indicate abnormalities in				point the way to more the genetic components
the amygdala, hippocampus, septum, mamillary				of spectrum disorders. The research also
bodies, limbic system, and the cerebellum.				advanced basic understanding in the genetic
Autistic brains are slightly larger and heavier and a				architecture of the genome of autistic individuals
larger than normal head circumference is				and will help in focusing future research.
commonly noted.				One practical aspect of this type of research may
In the limbic system, there is an excess of cells				be the development of a test that would confirm
and they are too small. The neurons themselves				the autism diagnosis in children exhibiting
appear to be underdeveloped. Dendritic trees				symptoms and identify families who carry genetic
which provide the basis for connections between				defects that could be inherited by their children.
neurons are truncated (i.e. shortened).				Mirror neurons
In the cerebellum, purkinje cells are widely				A theory featuring mirror neurons states that
affected. The anatomic differences correlate to				autism may involve a dysfunction of specialized
the curtailment of development earlier than 30				neurons in the brain that should activate when
weeks gestation. In other words, the				observing other people. In typically-developing
development of the cells appears to have				people, these mirror neurons are thought to
stopped at some time before the 30th week in				perhaps play a major part in social learning and
utero				general comprehension of the actions of others.
An enlarged third ventricle of the brain appears to

Power Advocates

Causes of autism