I have two close friends whose children each had symptoms similar to Asbergers/Autism whose lives have been transformed by changing their diet in ways that are generally aligned with the ideas in this study (unhealthy bacterial conditions in gut cause undigested proteins to leak through the gut into the bloodstream, where they cause problems when they bind to receptors in brain or other tissues).
There is a strict diet called the GAPS Diet that both of these families followed and they began to see substantive changes within months, and ongoing improvements over a couple of years that have really allowed these kids to blossom.
This is not hearsay. I knew these kids before and I know them after, and they have improved dramatically.