April is Autism Awareness Month, and April 2 is World Autism Awareness Day. These designations are less than ten years old but have already received widespread attention, in no small part to the rapidly increasing prevalence of autism spectrum disorders over the past two decades.
In 2000, the Centers for Disease Control and Prevention (CDC) reported the prevalence of autism at 1 in 150 children in the U.S. Updates on this every two years have shown a steady increase, and in March the latest reports indicate a prevalence of 1 in 68 children. Boys are at even greater risk, with a prevalence of 1 in 42 compared to girls at 1 in 189.
What this all means isn’t completely clear. The prevalence of a condition is the number of cases in the population at any one time. The increasing prevalence means that more people are being identified with autism now than ten years ago. This is not the same as an increase in the incidence of autism. Incidence is the rate of new cases per population occurring over a given time period. The CDC’s report of a prevalence of 1 in 68 children does not mean that a child born today has a 1 in 68 chance of having autism. The prevalence numbers include other factors, such as families knowing more about autism and bringing symptoms to the attention of health care providers. It also includes health care providers who are more knowledgeable of autism and less likely to miss a diagnosis. So, some of the reason for the rising numbers can be due to everyone being more aware and not overlooking cases that are out there.
But we can’t completely rule out the chance that the incidence is increasing as well. Researchers are very concerned about this and examining many possibilities. If the incidence is increasing, there must be a risk factor present. We have known for a long time that there is a high genetic component to autism. For example, if one identical twin has autism, the other twin has a much higher risk of also having autism than we see in fraternal twins, who are not genetically identical. Genetic studies over the past decade have identified hundreds of potential gene abnormalitiess, but no single gene abnormality stands out to explain the rising prevalence. Researchers are now looking at environmental factors that might be affecting individuals with certain genetic profiles as possible causes.
Whatever the underlying cause may be, what we do know is that over the past decade the professionals at Nationwide Children’s Hospital have been seeing a marked increase in the number of children referred for evaluation for possible autism. We have responded by rapidly growing our clinical services for this population. In 2005, we had one half day clinic seeing one new patient each week. Today, the Child Development Center is examining twenty new cases each week for possible autism, and identifying over five hundred new cases each year. Our Center for Autism Spectrum Disorders, which is our primary treatment program, has grown from one psychologist and a handful of behavioral therapy aides to several psychologists and over eighty aides, serving over two hundred families. April is indeed Autism Awareness Month, but for our autism programs every day is autism awareness day.
Daniel L. Coury, MD, is Chief of the Section of Developmental and Behavioral Pediatrics at Nationwide Children’s Hospital and a Professor of Clinical Pediatrics and Psychiatry at The Ohio State University College of Medicine.
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