The U.S. Centers for Disease Control and Prevention says 1 in 88 children is now diagnosed with autism. We asked autism experts the question: Is there an autism epidemic? One of Canada's leading researchers in autism had this to say:
Dr. Evdokia Anagnostou, child neurologist, clinician scientist, Bloorview Research Institute; assistant professor, department of pediatrics, University of Toronto:
There is no doubt that the rate of diagnosing autism spectrum disorders (ASD) has been increasing . . .
The question remains whether the increase in the diagnosis is due to a true increase in the incidence of autism spectrum disorder (the true risk of developing ASD) or whether other methodological factors account for this increase.
Possible culprits include changes in the diagnostic criteria, making the diagnosis earlier and earlier so that younger kids are included in the numbers, diagnostic substitution (we diagnose more ASD now than global developmental delay or language disorders compared to one to two decades ago), and increased awareness of the diagnosis, so that teachers, parents and front-line clinicians are more likely to look for signs and symptoms of ASD. All of these would have been predicted to increase the number of children diagnosed, and have been shown to do such in various studies.
The question still remains, after all of this is accounted for, is there a true increase in the incidence of the disorder?
We do not know the answer to that yet, but that does not mean that we should not be investigating this possibility. Specifically, although we know that ASDs have a strong genetic component, and we absolutely need to understand that more fully so that we can understand the biological paths that may be potentially targets for treatment, there are factors within and out of the human body that influence the degree of gene expression.
In other words, although children with autism carry genetic variations that either cause ASD or increase the risk of ASD, there may be interactions with the environment, whether this is the environment around conception (e.g., recent data related to paternal age), fetal environment or the environment outside of the body that may influence how these genes ultimately affect the function of brain and other biological networks.
As such, studies of the epidemiology of ASD, as well as our genome and gene-by-environment relationships, are still critical to fully answer this question.