Changes in autism spectrum disorder prevalence in 4 areas of the United States.
Rice C, Nicholas J, Baio J, Pettygrove S, Lee LC, Van Naarden Braun K, Doernberg N, Cunniff C, Newschaffer C, Meaney FJ, Charles J, Washington A, King L, Kolotos M, Mancilla K, Ervis CA, Carpenter L, Yeargin-Allsopp M. Disability and Health Journal. July 2010;3(3):186-201.

Researchers analyzed changes in the rates of ASD in four states from 2000 to 2004 and found that the prevalence had increased by an average of 55 percent in the locations showing change. Using data collected by the Centers for Disease Control and Prevention (CDC) Autism and Developmental Disabilities Monitoring (ADDM) Network, researchers found that prevalence rates had increased significantly in Georgia and Maryland (38 percent and 72 percent increases respectively). In Arizona, rates of ASD increased by 26 percent over the four years, but this figure did not rise to the level of statistical significance (meaning that the measured increase could have occurred by chance and may not represent the true prevalence change). In South Carolina, ASD rates dropped, but not by a statistically significant amount, effectively representing no change in prevalence. Investigators identified 8-year-olds who met the DSM-IV criteria for ASD by reviewing information about their development included in their available health and/or education records. The authors note that some of the increase in prevalence is due to heightened awareness, change in diagnostic criteria, earlier age of diagnosis, and the diagnosis of milder forms of ASD; however, taken together, these factors do not entirely explain the increase in prevalence and a true surge in the number of cases cannot be ruled out. Regardless of the cause, there is a dramatic change in the prevalence of ASD in some parts of the country, and more children are accessing services than ever before. In the face of such an urgent public health concern, the authors state that collaborative efforts to improve research and service systems for people with ASD will be essential, in addition to continued monitoring to better understand changes in prevalence.