Cause of Autism Part I

The causes and etiology of autism are an area of debate and controversy. There is as yet no consensus, and researchers are studying a wide range of possible causes to try and pinpoint what may be the cause of autism. Since autistic people are all somewhat different from one another there are probably multiple 'causes' that interact with each other in subtle and complex ways, and thus give slightly differing outcomes in each individual.

Further complications arise because there is no certainty that high-functioning Asperger's Syndrome actually has the same cause or causes as low-functioning autism. It is possible that Asperger's Syndrome and Autism have different causes.

There is a further complication due to the possibility of mis-diagnosis (such as of ADHD instead of autism spectrum disorder).

It should be noted that some of the theories given below apply more strongly to Asperger's Syndrome than Autism, and visa versa.

Physical Disorder Theories

Brain size
The majority of autistics have slightly enlarged brain size, compared to normal people. Neurology Today (Volume 2,8: August 2002) stated that "Although it is accepted that autistic individuals have, on average, an enlarged brain size, the nature of this abnormality remains unknown.". (See also the paper "Brain Volume in Autism" PDF link).

The extreme male brain theory
In his 2003 book The Essential Difference, professor Simon Baron-Cohen of the Autism Research Centre argued for the extreme male brain theory, which suggests that Asperger's Syndrome and autism represent an extreme form of the way in which men's brains differ from those of women. As a result, people with Asperger Syndrome are good (often very good) at systemizing and very bad at empathizing .

The theory is linked with Baron-Cohen's "empathizing/systemizing (E-S)" theory which states that, in general, men are better at systemizing than women, and that women are better at empathizing than men due to physical differences between male and female brains. Hans Asperger himself said that his patients had "an extreme version of the male form of intelligence."

The concept of differing types of intelligence in males and females is controvesial though, and remains largely speculative.

The preoperational-autism theory
The preoperational-autism theory states that autistic people are those who become neurologically impeded at the preoperational stage of cognitive development, where much of information processing is at a holistic-visual level and largely musical and nonverbal. This also addresses the issue of 'theory of mind', where children (autistic and non-autistic) at the preoperational stage of cognitive development have not attained decentralization from egocentrism.

Underconnectivity theory
Underconnectivity theory theorizes that autism is a system-wide brain disorder that limits the coordination and integration among brain areas. With the aid of MRI, it was seen that white matter, which connects various areas of the brain like cables, has abnormalities in people with autism. This theory may be related to the "lack of central coherence" theory proposed by Uta Frith, which suggests that children with autism are good at paying attention to detail, but have difficulty integrating information from a range of sources.

Mind blindness theory
This theory says that the autistic person has "mind blindness", or the inability to create accurate models of other people's thoughts. The typical example of this is the Sally-Anne test where the subjects have to try to determine what a third party's action will be (see theory of mind also). Some people with autism do not seem to fit this model, however.

Faulty mirror neuron theory
In some instances, brain areas that are active during the observation of hand-movements are silent in autistic individuals. The activity is markedly enhanced in non-autistic persons.  So the social deficits observed in autism could be the result of a faulty mirror neuron system, which could also prevent normal development/expression of empathy.

Blanket term
There is increasing suspicion among researchers that autism is not a condition with a single cause, but a number of yet unidentified conditions with different or variably co-mingling causes.

From Wikipedia, the free encyclopedia
 Part II >>