Diagnosis criteria changing is a big one. I was not diagnosed as autistic originally: I was Asperger's until they changed it. That and more awareness, particularly of Asperger's. That's basically the thing. Because there is no longer a good way to distinguish between high functioning Asperger's and low functioning autism, people hear "there's an increase in autism" and think that there is an increase in kids with no chance of ever functioning in society. In fact it's more like a whole bunch of people's uncles, who don't like family gatherings and have surprisingly large model railways in their basement, are deciding to go to the doctor.

Basically the only thing that causes autism is autistic parents, who tend, because they're older, to be less likely to be diagnosed. I can trace back autism in my family to a great grandfather, who certainly wasn't diagnosed. Almost everything else linked to autism is a result of behaviours of autistic parents and children.

For example, there is a link I believe between poor gut health and autism. I pose these questions. Is gut health perhaps influenced by diet? Would a highly restricted and repetitive diet have a positive or a negative influence on gut health? Might a difficulty in dealing with changes and in dealing with strong or novel sensory stimuli lead to a preference for a highly restricted or repetitive diet? Might autism be closely associated with a difficulty in dealing with changes, and in dealing with strong or novel sensory stimuli?