Nearly all books, lectures, and websites on developmental disorders claim that they are increasing annually as it were an established fact. As a matter of fact, the National Rehabilitation Center for Children with Disabilities, an institute with which I am very familiar, states that the number of children who seek consultation for cerebral palsy or epilepsy has dramatically declined and children with developmental disorders account for the majority of patients, which makes me think they are actually on the rise. In my work as a pediatrician which I have continued over the years, children with cerebral palsy or epilepsy have declined to less than 10 percent, so it is true that the proportion of patients with developmental disorders have increased among the total patients I receive.

Nevertheless, I still have doubts about this and ask myself if we are really seeing an increase in children with developmental disorders.

This is not just a fanciful doubt; it is now supported by rather solid evidence.

First, the causes of developmental disorder are not yet fully understood, but it is a fact that most researchers worldwide acknowledge a genetic relation. The Genome-Wide Association Study, a comprehensive research project, is now underway to study autistic spectrum disorder and ADHD (Attention Deficit Hyperactivity Disorder). In this project, approximately 1000 people with a confirmed diagnosis of either autism spectrum disorder or ADHD agreed to provide genetic samples (blood tests, tissue samples, etc.). The genomic sequence was then compared to that of a number of neurotypical samples, and this has resulted in the discovery of a number of candidate genes.

Human gene sequences do not change over a period of several decades. If developmental disorders have a genetic cause, it is unlikely they should have started to increase recently.

That said, we have recently found that through chemical bonding in DNA, which is the highly polymerized compound that makes up our genes, the expression of genetic information changes even if the genes do not change themselves, and there are also some researchers who claim that this can explain the rise in developmental disorders....

In the case of increasing obesity and incidence of cancer, this has been mainly substantiated by long-term epidemiological studies conducted by a national and major research institutes. In the case of developmental disorders, however, such long-term studies have not yet been conducted.

I would also like to point out that diagnosis under the name of development disorder is made all too often. In my practice, I treat a number of children who were diagnosed with autistic spectrum disorder at a young age. In many cases, doubtful of the diagnosis, the parents bring their children to me for a second opinion. In fact, however, a significant percentage of them do not have autistic spectrum disorder, and include children whose condition can be explained by individual nature and individual differences in development.

My diagnosis may lack rigor, but some might say that it is the experts who readily diagnose delayed language development, difficulty with group interaction, or slightly repetitious behavior as autistic spectrum disorder who are "increasing" developmental disorders including autistic spectrum disorder.

My true feeling is that the real cause of the increase in patients seeking treatment for developmental disorders stems from the rise in social awareness of developmental disorder, and it seems to be that some of them have been overdiagnosed.