The global prevalence of autism has increased twenty fold
to thirtyfold since the earliest epidemiologic studies were
conducted in the late 1960s and early 1970s. At that time,
prevalence estimates from European studies were one in 2,500
children in the population (2), and by the 2000s prevalence
estimates from large surveys were 1%–2% of all children (3–5).
Although the underlying reasons for the apparent prevalence
changes are difficult to study empirically, select studies suggest
that much of the recent prevalence increase is likely attributable
to extrinsic factors such as improved awareness and recognition
and changes in diagnostic practice or service availability (5,6)