Cases somebody genetically may be predisposed to certain conditions such as autism or at least along the spectrum and often there's a trigger mechanism of some kind that sets off a pre-existing condition. Violence in the home drug abuse too much digital stimuli and possibly something as simple as a vaccination. Anyone who disregards this as a possibility flat-out is not looking at the entire argument. Anti-vaxxers are jumping on a train that has no real support those disregarding vaccination is a possible trigger for the anyone with a pre-existing condition are also doing the same. Wait and see I'm sure we'll learn more in the future