Autism is a complex biological disorder that generally lasts throughout a person’s life. It is called a developmental disability because it starts before age three, in the developmental period, and causes delays or problems with many different ways in which a person develops or grows, such as communication, social interactions and routines or repetitive behaviors. These symptoms cut off people with autism from the world around them.

Genetic studies of autism conducted by the CPEA Network highlight some of the ways genes may be involved in autism, using a process called linkage analysis to identify genetic "hotspots," or chromosome areas where defective genes related to autism may be found. So far the most promising leads seem to be on Chromosome 7, where genes for other language disorders are known to exist, and Chromosome 15 where genes for other developmental disorders have already been identified.

Some parents and families of children with autism believe that the Measles/Mumps/ Rubella (MMR) vaccine caused their children’s autism. However, to date there is no definite, scientific proof that any vaccine or combination of vaccines can cause autism. In 2000, the Institute of Medicine (IOM) at the National Academy of Sciences, at the request of the Centers for Disease Control and Prevention (CDC) and the NIH, conducted a review of all the evidence related to the MMR vaccine and autism. The IOM concluded that the evidence reviewed did not support an association between autism and the MMR vaccine.

Rett syndrome is one of many conditions classified as an autism spectrum disorder, which means it is not autism but has features that are similar to autism. This disorder causes autism-like symptoms, such as poor language skills, repeated hand motions, and decreased social contact in girls. These symptoms begin sometime between ages six months and 18 months, after apparently normal development.

* The NICHD/NIDCD Network on the Neurobiology and Genetics of Autism: the Collaborative Programs of Excellence in Autism (CPEAs)--describes the largest single, autism-specific research effort to date. http://www.nichd.nih.gov/autism