I am from Southern India (typically darker skin) and have noticed 6 cases of ASD (non-verbal and very basic or non-existent social interaction) amongst friends and relatives. 3 of these cases come from the same family (mine) and the other 3 are unrelated. All 6 were born either in the US or UK. All 4 families don't have previous occurrence of ASD or similar symptoms (non-verbal or awkward social skills would be easy to pick up).

Since reading/experiencing a family member with ASD, I do see some ASD characteristics and behaviors in some other family members residing in India but they somehow have been able to overcome that and lead a typical life. Can't explain why there aren't more severe cases (in which case, they would've been reported) and if more sunlight or exposure to a lot more people/social situations is helping correct it.

There was an Indian news article that reported a higher incidence of ASD in NRIs (non-resident Indians). With Desk jobs becoming more prevalent, Vitamin D deficiency is showing up in India as well. Given my small #samples, it does seem like something is triggering more severe ASD in people with dark-skin in countries with less sunlight. Increase in incidences of ASD, can be attributed to its broadened definition but there seem to be other minor reasons (Vitamin D being one) which need more research instead of dismissal. Current incidence levels of 1 in 68 (boys - 1 in 42, girls - 1 in 189) is plain crazy and needs more attention.