). ▁This ▁estimate ▁is ▁a ▁ 1 5 % ▁increase ▁from ▁the ▁ 1 ▁in ▁ 6 8 ▁rate ▁in ▁ 2 0 1 0 , ▁ 8 6 % ▁increase ▁from ▁the ▁ 1 ▁in ▁ 1 1 0 ▁rate ▁in ▁ 2 0 0 6 ▁and ▁ 1 5 4 % ▁increase ▁from ▁the ▁ 1 ▁in ▁ 1 5 0 ▁rate ▁in ▁ 2 0 0 0 . ▁Di agnostic ▁criteria ▁of ▁AS D ▁has ▁changed ▁significantly ▁since ▁the ▁ 1 9 8 0 s ; ▁for ▁example , ▁U . S . ▁special - ed uc ation ▁aut ism ▁classification ▁was ▁introduced ▁in ▁ 1 9 9 4 . ▁ ▁Aut ism ▁is ▁a ▁complex ▁ne uro development al ▁dis order . ▁Many ▁causes ▁have ▁been ▁proposed , ▁but ▁its ▁theory ▁of ▁caus ation ▁is ▁still ▁question able ▁and ▁ultimately ▁unknown . ▁The ▁risk ▁of ▁aut ism ▁is ▁associated ▁with ▁several ▁pr en atal ▁factors , ▁including ▁advanced ▁pat ernal ▁age ▁and ▁di ab etes ▁in ▁the ▁mother ▁during ▁pre gn ancy . ▁AS D ▁is ▁associated ▁with ▁several ▁gen etic ▁dis orders ▁and ▁with ▁ep ile ps y . ▁Aut ism ▁is ▁believed ▁to ▁be ▁largely ▁inherited , ▁although ▁the ▁gen et ics ▁of ▁aut ism ▁are ▁complex , ▁and ▁it ▁is ▁unclear ▁which ▁gen es ▁are ▁responsible . ▁Little ▁evidence ▁exists ▁to ▁support ▁associations ▁with ▁specific ▁environmental ▁expos ures . ▁ ▁In ▁rare ▁cases , ▁aut ism ▁is ▁strongly ▁associated ▁with ▁agents ▁that ▁cause ▁birth ▁defect s