Advance of research, check it out, come to your own conclusions.
Years ago, I saw a large summarized chart of what therapies were working well. Two things works: a diet of low/no casein and gluten (no milk & bread) and chelation therapy. Therefore, the conclusion was: this is toxic overload that somehow damages the system that properly digests wheat and milk. Now, there are more questions about hybridized wheat and polluted milk. Still, toxicity.
But there may be more to it.
Notice, however, there is hope. IF you look at the edges, and not at convention. Convention will tell you there is nothing that can be done and then charge you most of your wealth forever. By contrast, the folks working on this toxicity thing were villianized — but had people who were no longer autistic! Yes, you read that right. There are some.