According to the CDC, one in 68 children in the United States has an autism spectrum disorder (ASD). In Denmark, that number is one in 100. The prevalence of ASD has increased significantly over the last thirty years. In order to explain this increase, everything from vaccines to pesticides to mercury have been blamed all of which have been disproved by scientific research. Well, now we have an explanation that makes sense. According to a new study done by researchers of Aarhus University in Denmark, the increase is largely due to changes in reporting practices.
Researchers led by Stefan N. Hansen, M.S., of Aarhus University collected data from about 678,000 children born in Denmark between 1980 and 1991. These children were followed from birth until ASD diagnosis, death, emigration or until December 2011. Of those children, about 4000 were diagnosed with ASD, and the majority of those diagnoses were made after 1995.
In 1994, changes were made to the diagnostic criteria which defined autism as a range of disorders, allowing more mild cases to be defined along the spectrum. In 1995, the national health registries of Denmark included diagnoses made outside of hospitals. These changes explain 60 percent of the increase in prevalence of ASD diagnoses, according to the researchers.
Therefore, researchers conclude, This study supports the argument that the apparent increase in ASD prevalence in Denmark in recent years is in large part attributable to changes in reporting practices over time, However, a considerable part of the increase in ASD prevalence is not explained by two changes in reporting practices. Thus, the search for etiologic factors that may explain part of the remaining increase remains important.
ACSH s Ariel Savransky adds, Although this study was conducted in Denmark, the results may also explain the increased prevalence of autism spectrum disorder in the United States as well. However, the recent Diagnostic and Statistical Manual of Mental Disorders Fifth Edition did contain an updated definition of Autism Spectrum Disorders requiring more criteria to be met in order to be diagnosed with ASD. It would be interesting to see how this change affects the numbers in the US. However, the bottom line is that the studies done so far that have allegedly linked autism to environmental factors and vaccines have no basis in science.