Age and type of onset as critical variables in early infantile autism.

A retrospective study of 131 autistic children was made in which 2 groups, Natal and Acquired, were defined on the bases of age at onset and type of onset. Prenatal and perinatal variables were found to be significantly related to Natal onset, whereas in the Acquired group the significant variables were those occurring in early childhood, between years 1 and 3. Follow-up data on intellectual functioning and language development indicated a better prognosis for the Acquired group. An inability to cope with stress is postulated as an underlying feature in both instances, present from birth in the Natal group and occurring in the face of developmental stresses in the Acquired group.