03/30/2012 04:36 pm ET Updated Mar 30, 2012

What Is Autism?

Just this week, a report from the Centers for Disease Control showed that rates of autism have increased in the U.S. from one in 110 children to one in 88 children.

But what, exactly, is autism?

Autism is a spectrum disorder, meaning the symptoms can range from mild to severe. There are three different kinds: autistic disorder, Asperger syndrome and pervasive developmental disorder- not otherwise specified (also called PDD-NOS, or atypical autism), according to the CDC.

Symptoms of autistic disorder include being withdrawn, problems with social skills and communication, language and unusual behaviors, while symptoms of Asperger are milder versions of the same. PDD-NOS symptoms are even milder than both autistic disorder and Asperger syndrome, and someone with PDD-NOS may only have some social or communication problems.

There is no known cause of autism, though experts say it may be a combination of genetic and environmental factors. Despite concerns, there have been no studies confirming a link between autism and measles-mumps-rubella (MMR) vaccines, according to the Mayo Clinic.

Autism symptoms typically begin to show before age 3, according to the NIH. WebMD reported on a study showing that certain tests might be able to predict autism as early as 14 months old. That study, conducted by researchers from the Kennedy Krieger Institute, demonstrated that by using tests on motor and language development, doctors were able to predict 70 percent of future autism cases among the study participants.

However, the Centers for Disease Control and Prevention says on its website that a reliable diagnosis of autism usually can't be made until age 2.

A doctor may recommend testing for autism if a baby isn't babbling by the time he or she reaches one year old, isn't gesturing by one year old, isn't speaking words by 16 months, doesn't seem responsive to social cues or has trouble making eye contact, according to the National Institutes of Health.

There is no cure for autism, though research has shown that the earlier autism is treated, the better.

A 2009 study from researchers at the University of Washington looked at a form of therapy called the Early Start Denver Model, which involves amping up the child's communication and social interaction skills, the AP reported.

The Early Start Denver Model study showed that kids ages 18 months with autism were able to have their symptoms improved after undergoing two years of therapy.

Different forms of therapy -- behavioral, communication and educational -- can help children with autism to function better, the Mayo Clinic reported. Medications can also help alleviate symptoms, like anxiety or behavioral problems.