Autism spectrum disorders (ASDs) are a group of developmental disabilities that range from mild to severe and are characterized by social impairment, difficulty communicating, and repetitive motions or other unusual behaviors.106 These characteristics are usually noticeable before the age of 3 and remain as a lifelong chronic condition with both medical and psychological implications.107 ASDs include autistic disorder, Asperger’s disorder, pervasive developmental disorder–not otherwise specified (PDD-NOS), Rett syndrome, and childhood disintegrative disorder.108 Based on 2008 data from the 14 sites in its Autism and Developmental Disabilities Monitoring Network, the Centers for Disease Control estimates 1 in 88 8-year-old children have ASDs.109 Prevalence in these sites had increased 23 percent from two years earlier and 78 percent since 2002. Although there is disagreement about whether the true prevalence has increased (since guidelines for diagnosis have changed, more services are available, and awareness of ASD has increased), the CDC numbers are based on evaluation records, not parental reports. Measuring ASD prevalence continues to be a challenge due to the complexity of the disorder, the lack of consistent and reliable diagnostic standards, and changes in the definition of such conditions.110 ASD prevalence is about five times higher in boys than in girls (ratio of 4.5 boys to 1 girl). Prevalence is also significantly higher among non-Hispanic white children than among black and Hispanic children. Intellectual ability is highly variable, with 38 percent reported as intellectually disabled, 24 percent as borderline, and 38 percent with average or above average intellectual ability.
There are controversies about what should be included in the category of autism spectrum disorders. The NIH classifies Rett syndrome as an ASD, but some argue that it is more similar to non-autistic spectrum disorders such as fragile X syndrome or Down syndrome. Unlike other ASDs, Rett syndrome is also almost always in girls.111 There is also debate over whether Asperger’s disorder is a separate disorder or simply a less severe form of autism.112 The next revision of the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM) will drop individual classifications for autistic disorder, Asperger’s disorder, childhood disintegrative disorder and PDD-NOS, grouping all of them under “autism spectrum disorder”—a term that is already widely used. APA has said this change will help “more accurately and consistently diagnose children with autism.” Rett syndrome will be dropped from the DSM altogether. There is concern among the Asperger’s and Rett communities that these changes will result in a loss of identity among individuals with these specific disorders and that it may affect health insurance coverage and school funding for special education.113
The exact causes of ASDs remain unknown, but research suggests genetics and environment both play important roles. Researchers are studying factors such as family medical conditions, parental age and other demographic factors, exposure to toxins, and complications during birth or pregnancy. CDC and IOM studies have found no link to childhood immunizations.114, 115, 116, 117