The incidence of autism has been on the rise for 40 years. We don’t know why, but the terrible burden of suffering has spurred people to urgently look for a cause. As there are all kinds of secular trends over the same time period, correlating this rise in autism with corresponding changes in environmental parameters, led to the “discovery” of all kinds of spurious or incidental relationships.
When attempting to establish causal relationships, experimental work is indispensable, but unethical to do in humans.
Now, it has been shown that feeding maternal mice a high fat diet led to social behavioral deficits reminiscent of autism in offspring. These deficits were associated with a disrupted microbiome, specifically low levels of L. reuteri. Restoring levels of L. reuteri rescued social behaviors, linked to the increased production to oxytocin.
I’m aware of the inherent limitations of mouse work (does anything ever transfer?), but if this does (and I think it will – given recent advances in our understanding of the gut microbiome in relationship to mental), it will be transformational, not just for autism.
Here is a link to the paper: Microbial reconstitution reverses materal diet-induced social and synaptic deficits in offspring.