Autism is a behavioral disorder with a number of symptoms that may range from mild to severe. No two children with autism may have exactly the same symptoms or the same experience, yet it's a disorder that is shared among many. One in 88 American children has been diagnosed with an autism spectrum disorder, according to the CDC, and the disease currently affects up to 1.5 million Americans. The numbers of autistic people rise by as much as 10 to 17 percent each year, increasing at a faster rate than any other developmental disability.
So what is autism, and what does it mean for children?
Autism falls into a group of disorders called autism spectrum disorders, or ASDs. Autism and other ASDs are considered developmental disabilities, which means that they impair a child's ability to grow and develop normally.
Autism spectrum disorders include:
"By definition, autism spectrum disorders affect three domains of functioning for a child," said Bradley Peterson, MD, director of child and adolescent psychiatry at the Columbia University Medical Center in New York. "The domain that people feel is most central is the area of social interactions."
The normal give and take between people in conversation, or social reciprocity, "is almost always impaired in autistic children," said Dr. Peterson
The other two areas of functioning that are seen in children with autism are difficulty with spoken language and a tendency toward repetitive interests, thoughts, and behaviors.
"By definition, all of these things have to be present by the age of 3, and they have to be disproportionate to the overall intelligence level of the child," said Peterson. "Mentally retarded children may appear somewhat unusual in some of these domains, but it would be typical with their intellectual mental age."
Common symptoms of autism include:
What causes autism is still largely a mystery, but several theories exist.
"It's very clear that autism has numerous causes," said Peterson. "Those numerous causes are almost certainly going to have different manifestations in the brain different genes are known to cause autism, and we know that those genes will have different effects on different parts of the brain in terms of behavior and thinking."
But, Peterson noted, more and more research is being done that provides useful information about how autism affects the brain.
"Social interaction is a very complex behavior, and many brain regions are involved in supporting that complex ability," Peterson said. That means that even if researchers discover the effect that autism has on one brain region, there are still many more to be discovered.
Researchers also haven't yet discovered exactly when autism strikes it's not yet known if children are born with it or if it's a disability that develops later.
"We do know that some children [as infants and toddlers] appear quite normal in most, if not all, respects," said Peterson. The same children can go on to develop autism. However, that's certainly not common; most autistic children show signs and symptoms of autism early on.
Autism research has come a long way and shows a lot of promising signs for understanding the roots of the disorder, but there are still many questions remaining and much more research to be done.