What's autism? Symptoms vary among people with disorder

The gap between the reality and public image of autism is getting wider.

Autism still inspires thoughts of Dustin Hoffman in "Rain Man," gifted yet odd individuals who carry out pi to 1,000 places or recite "Moby-Dick" from memory.

Autism, though, is far more complex and varied. The neurological disorder, one of the autism spectrum disorders, has a range of symptoms. People on this spectrum can be gifted or can struggle with severe developmental delays. They can engage their parents or appear trapped in their own worlds.

They are bound together by struggles with social, emotional and communication skills, according to the Centers for Disease Control and Prevention.

These struggles appear in a long list of symptoms. Low-functioning individuals may rarely, if ever, talk; while those higher on the spectrum can be found in regular elementary school classrooms, colleges and mainstream jobs.

With the prevalence of diagnosed children exploding -- the population soared more than 500 percent, according to one 10-year government estimate -- a lot of autistic children fall outside the traditional narrow definition. "Clearly, we are in a process of changing our definition of what it means to have autism," said Annette Estes, co-director of the University of Washington's Autism Center Research Program.

The latest CDC estimate says as many as one in 150 children has autism. Boys are four times more likely to get diagnosed than girls.

There are no blood, genetic or prenatal tests to detect the mysterious disorder. Instead, a child's diagnosis is often based on clinical observations, psychological and language testing, parent interviews and other criteria, according to the CDC.

There are likely genetic causes, but there also may be environmental triggers.

Debates, sometimes disturbing in their intensity, rage in academia, the blogosphere and among parents about what causes autism and how to treat it.

It's become so complicated that some researchers have begun referring to "autisms," suggesting there will eventually be subtypes.

One consistent trait is that autism typically shows up by a child's third birthday.

The emergence can be particularly heartbreaking. A child may hit all of the developmental milestones only to begin losing those gains around age 2. Parents complain their child slips away, appearing to withdraw into his or her own world.

Still other children remain engaged, yet struggle with other symptoms.