What is your opinion on what causes autism?

There are many different opinions on what causes this disorder that has now reached "epidemic proportions". Though no one seems to have any definative proof of any one thing, there are lots of theories. I am esp. interested in hearing attempts to tackle this question answered by parents, teachers, doctors and siblings of autistic people and if possible, any autistic person who is able to give their opinion. I would also like to hear from men and women who have been involved in scientific studies of this lifelong disability.