"Maternal immigration is associated with substantial increased risk of autism-spectrum disorders with differential risk according to different region of birth and possibly ethnicity."There's the notable "epidemic" among Somalian immigrants. This could conceivably have something to do with (I guess) higher selenium levels in Somalian diet (due to lower rainfall, different geology, or the high fish content of the local diet). People moving to a diet of less selenium than they had evolved for could be more vulnerable to the antiinnatia effect of mercury, in absence of less antidoting selenium.
But while I don't rule out that possibility, a more likely process appears to involve vitamin D deficiency. Indeed a theory of causation by vitamin D deficiency has already been published in Medical Hypotheses (before that journal's editorial decisions recently became subject to non-editorial interventions by the owner, the publisher of supposedly scientific journals Elsevier).
This vitamin D deficiency thesis would tie in solidly with the antiinnatia theory, for the reason explained by the popular health writer Joseph Mercola:
"In fact, there’s compelling evidence that vitamin D is in fact KEY for proper gene expression." "Each cell in your body has its own ‘DNA library’ that contains information needed to deal with virtually every kind of stimulus it may encounter, and the master key to enter this library is activated vitamin D."In other words, Mercola is here stating that vitamin D deficiency is something of an antiinnatia factor. So of course it would tend to cause autism (at critical developmental periods). Indeed, I indicated in my 1993 paper (and indeed all versions from 1982 onwards) that deficiencies of nutrients could obviously be antiinnatia factors.
Questions now arise as to how much contribution to antiinnatia (autism etc) is made by vitamin D deficiency, and whether the relationship with mercury, antiinnatia genes, etc is additive or synergistic.
Of course using vitamin D deficiency to raise one's infant's IQ would have certain major downsides, probably even worse than dosing them with extra mercury vapor; so farbeit from me to recommend it as a sort of "smart" drug.
P.S.: Vitamin D deficiency as an antiinnatia factor could also be the basis of recent observations of seasonal variation of autism incidence (by birthdate).
One might next predict that if D deficiency is indeed an antiinnatia factor, then IQ should also be season-of-birth dependent. It looks like that may not be the case. But then quite possible reasons for that could be that in the populations studied there was not much sunlight exposure anyway, and schoolchildren were routinely supplied with cod liver oil and orange juice (as in the uk for many years) such as would prevent substantial deficiency.