“Autism” or more correctly ASD has but one cause – genetic: period.
ASD is a wide collection of neurological differences which affect behaviour, sensation and interaction with the outside world: period.
The “ASD individual” is cast in stone either at conception or in the first divisions of life and the main effect constructed in the second and third trimester.
ASD individuals who MAY go on to have difficulties with their neurobiology MAY develop noticeable differences as they interact with the outside world, particularly during the rapid neurological development stages of life (ALL of them).
ASD individuals may go on to learn there own or be provided aided mechanisms to improve the way they perceive and interact with the outside world.
Environmental factors PROBABLY have a large effect on how the individual is effected by these neurological effects. The complexity of the immune system and it’s control may have a great affect on the “expression” of ASD differences. Since there have been a great deal of observations of the neurobiochemical and neuroanatomical differences in ASD individuals AND when they have had a large immunological challenge, it seems to me that the effect is merely concomitant – i.e. the immunology is doing something to the “neuropathlogy” that is already there.
The site suggests a figure of 90% causation. Simply looking at the geographical prevalence of Lymes indicates that these numbers just don’t add up. Similarly with immunization and many of the other direct “causes”. If an external biological or chemical agent was the cause of these range of conditions then the removal of the agent should remove the effect – unless SPECIFIC and REPRODUCIBLE “damage” can be attributed to the agent – as far as I understand there is no proof of this or even a theoretical mechanism.
I believe one of that in addition to the current lack of specific understanding one of main reasons that so many different “causes” is simply due to parents’ reluctance to accept the genetic issues. Simple observations on the way ASD clusters in families should indicate to everyone that this is a erroneous stance.
Similar to neurological advancement (in a evolutionary sense) a human’s immune system is very advanced. My belief is that the two systems are so genetically intertwined that disturbances on one can greatly effect the other.