Autism rates rising ... but why?

In early 2012, the U.S. Centers for Disease Control and Prevention issued findings from a study that found 1 in 88 children is now diagnosed with autism spectrum disorder by the age of eight. This is a 23 percent increase in ASD diagnoses in just two years. What troubles doctors is that the rate has risen far above the 2006 estimate of 1 in 110.

The National Institute of Neurological Disorders and Stroke says that ASD includes a range of complex neurodevelopmental disorders, characterized by social impairment, communication difficulties, and restricted, repetitive, and stereotyped patterns of behavior. Children with ASD can have difficulties learning what are typically simple lessons for other children. Although ASD varies in severity, the common thread is that it occurs in all ethnic groups and affects every age. Males are four times more likely to have ASD than females.

Doctors do not understand why autism rates have risen so profoundly. Some believe that a broader definition of autism is fueling these growing numbers. Diagnostic criteria has changed, and ASD is now encompassing conditions that weren't first included under the autism banner. Currently, ASD is classified into the following subsets.

Pervasive developmental disorders (not otherwise specified, or PDD-NOS): These are a large group of disorders characterized by delays in communication and socialization skills. Children may vary in their abilities, intelligence and behaviors. A PDD is typically diagnosed by age three.

Asperger's syndrome (AS): AS is a developmental disorder that includes repetitive routines or rituals, peculiarities in speech and language, such as speaking in a formal manner or monotone, socially and emotionally inappropriate behavior and the inability to interact with peers, clumsy motor movements, and problems with nonverbal communication. Unlike children with autism, children with AS retain their early language skills, but their condition may be realized due to motor development delays, says the National Institutes of Health.

Autism disorder (AD):