rainbow
Flicker photo by Cessna 206On the spectrum.

For all that the phrase conjures images of rainbows and bright happy days, it's not.

It's a term that parents often use to say their child has autism.

As the parent of a (thankfully) normally functioning child, that always confused me. I thought you either had autism or you didn't, and what do rainbows have to do with it?

To quote the Facebook status, it's complicated.

Autism is a "spectrum disorder," and not a syndrome or disease, precisely because it can't be diagnosed with a lab test. A child does have it or not, but it varies in intensity from severe to mild. You've probably met plenty of children with autism and never even knew it.

Trained experts, and usually the child's parents, can certainly tell in even the milder cases. These children act "different" from other children when it comes to certain patterns of development and behavior in four specific categories:

How they socialize and relate to others

How they talk

Behaviors they repeat over and over

How they sense the world and react to it

It's how a child behaves in these four categories that determines whether a child has autism, and where he or she falls on the "spectrum." It's not like a child can be ranked 8 on a scale of 10. A child with autism could have near-normal language skills but extreme sensory issues like screaming at the sound of the phone ringing or "seeing" music.

"You can have ten children in a room, each with ASD, and each child will display it differently in terms of how he or she relates socially, behaves, and communicates," says Nancy Wiseman, president of First Signs and author of The First Year: Autism Spectrum Disorders An Essential Guide for the Newly Diagnosed Child.

Invariably, experts will use those differences to place children with ASD into one of three (or four) general categories of autism:

Classic Autism

The most severe kind. Children can't communicate or relate to people normally and are hypersensitive to sounds colors and textures. They cling to rituals and change upsets them.

Asperger Disorder

Children with this condition speak normally and are very intelligent but have restricted areas of interest. They may lack empathy for others and have reduced ability to engage in two way conversations. They are often uncoordinated and assume odd body postures. They have trouble understanding expressions and interpret verbal statements literally.

Pervasive Development Disorder (PPD)

This is what you diagnose when a child appears to have classic autism, but doesn't qualify for some reason or another. They may have some but not all of the characteristics of autism or one of the other disorders. They have better social skills than children with classic autism, but still have trouble interacting, relating to, and communicating with others, and are sensitive to noises, colors and textures.

Sometimes experts will also include the following disorder within the autistic spectrum, despite its genetic origins:

Rett Syndrome

This rare gene disorder that affects mostly girls and occurs during the first 6 to 18 months of life. It is marked by severe impairments in thinking, learning, social and communication skills, as well as use of hands, hand wringing, screaming fits and other problems.

For more resources, go to:

First Signs

Autism Speaks

Center for Autism Research at Children's Hospital of Pennsylvania