What's more, in recent years, researchers have begun to find links between the makeup of microbes that call our guts home and neurodevelopmental disorders, like ASD.

Nevertheless, this connection isn't always consistent, and some experts have argued it isn't gut bacteria that trigger ASD, necessarily; it could be that kids with autism are more likely to restrict their diets because of 'picky' eating, which in turn influences the kinds of bacteria that persist in the digestive tract.

I'm not a scientist but diet and microbiome changes being a symptom of ASD seems more plausible than the other way around IMO.