Over the last two decades, the number of children diagnosed with autism, or autism spectrum disorder (ASD), has risen at an alarming rate.
Just a couple of years ago the U.S. Centers for Disease Control and Prevention (CDC) estimated one in 88 school children had some form of autism. That was a 23% increase over 2009's count and a 78% rise over 2007.
In a new report, the CDC puts that number at one in 50 school age children.
What's behind this condition that was unknown to much of the population just 30 years ago? First, let's look at what exactly health professionals mean when they speak of autism.
Biology and chemistry
Autism is a physical condition linked to abnormal biology and chemistry in the brain. According to the National Institutes of Health (NIH) most parents of an autistic child can tell something is not quite right by the time the child is 18 months old.
Health experts say there are many different symptoms and different types of autism, which may explain in part the rapid rise in diagnosis. Generally, the symptoms affect the way the child communicates and interacts socially.
Austic children, for example, often have difficulty speaking. Because of that, they might seem overly quiet. They may have a hard time using their imagination while playing and usually play alone, since they have a hard time making friends. There are different levels of severity of the disorder.
These symptoms may show up earlier than doctors generally believe. Researchers writing in the American Journal of Psychiatry say their just-completed study found children later diagnosed with autism have subtle but measurable differences in attention as early as seven months of age. These children, the study found, are slower to move their eyes from one object to another, compared to other children.