There are children and adults who have autism spectrum or pervasive developmental disorder (PDD). The spectrum of conditions that fit into this category is quite broad.
First there is no single cause.
It is a communication, processing disorder. Individuals may have normal or above normal intelligence. Some children may have severe cognitive limitations. Some of the kids have some amazing strengths but suffer with social skills. They are not sensitive to social cues.
In some cases there is a disconnection with sensory processing. Some aspects of either receptive or expressive communication is disconnected. I do not know what the disconnect may be. In different individuals or cases it could be a different process entirely.
There is a proven chromosomal abnormality is some people with autism spectrum, but the majority have no proven link.
There is no proof that vaccines have caused the increase in autism. The link between some vaccines and autism is more temporal than causal. The first year of life is more motor driven whereas the second year is dramatic with cognitive and verbal development.
Of primary concern is the increasing prevalence of vaccine preventable disease due to parents choosing to not vaccinate their children. We will see more death and illness that is preventable.
My primary concern is that there is some common environmental link. Research is being done and all of us need to keep an open mind. Autism is a devastating condition and requires early diagnosis and intervention. Early implementation of OT and Speech can have a tremendous impact on our kids.