>"Results lend support to previous studies that found higher rates of ASD intellectual disability in children of immigrants from low human resource index countries compared to other groups."

>coming from Somali also means coming from a low human resource index country. all kinds of air/water pollutants and chemicals/pesticides might be at play -together with- vitamin D deficiency.

>Vitamin D effect itself is hard to isolate from just this.

If anything, your link confirms vitamin D theory even more :) What is the most common trait for all these low human resource index countries? They are closer to equator, i.e darker skin of the population.

https://en.wikipedia.org/wiki/List_of_countries_by_Human_Dev...

It is very well established epidemiological fact that darker skin immigrants have noticeably lower vitamin D in higher altitudes (i.e where the higher developed countries are that they immigrate into).