The Huck Institutes of the Life Sciences

Increasing prevalence of autism is due, in part, to changing diagnoses

The greater than three-fold increase in autism diagnoses among students in special education programs in the United States between 2000 and 2010 may be due in large part to the reclassification of individuals who previously would have been diagnosed with other intellectual disability disorders, according to new research led by Santhosh Girirajan.
http://news.psu.edu/story/363374/2015/07/21/research/increasing-prevalence-autism-due-part-changing-diagnoses