Is there an Autism Epidemic?
As of right now, there is no evidence for an autism epidemic. However, many media sources are pushing through causes of autism epidemics ranging from vaccines, environmental toxins and isolated genetic populations. However, many of the sources do not look at the actual facts of what could be behind this increase in prevalence. First, there are many different DSM versions, each with diagnostic criteria for autism that has become progressively more inclusive and more exclusive. The newest DSM criteria has the capacity to include more people than ever before and can pull people out of incorrect diagnoses such as schizophrenia. This would inherently lead to an increase in the number of individuals diagnosed with autism. Allow with the diagnostic changes, data from the Individuals with Disabilities Education Act (IDEA) has shown an increased number of children with autism. However, this increase is mainly due to the fact that before the early 1990s, autism was not able to be reported by the state as a disorder. Therefore, going from 0 to 100 people with autism would seem like an amazing increase. Comparable to this is the fact that traumatic head injury was also available to be reported at the same time and has had similar increases in prevalence, yet people do not believe that there is an inherent increase in the amount of brain injuries.
A Simple Comparison: Crayons and Autism
In 1952 the DSM included 203 disorders; in the most recent DSM from 1994, there were 400 disorders. Similarly, in 1952 there were 48 different crayon colors made by Crayola, yet by 1993 there were 96 different crayon colors available. This corresponds to about a 200% increase over a time period of 40 years. So the question is, have people and colors become more disordered as chaos theory may suggest, or is something else going on to correspond to these dramatic increases? Similar to what is discussed in the editorial from the Pittsburgh Post-Gazette titled, “Children Have Always Had Problems, We Just Have Names For More of Them,” having more names for disorders or colors in nature is not the reason for an absolute increase in prevalence. Instead, the reason for the increase is a simple increase in the number of classifications and guidelines for things once considered the same. For example, some children may have been considered hyperactive in the 1950s, but by 1994 there was a diagnosis that explained the hyperactiveness. Other disorders that may have been present in the past may also have been primarily adult disorders, but with more evidence and research, it was discovered that a similar set of patterns emerges in children, thus creating the need for a new disorder to be described. Similarly in crayons, there used to be “blue” and maybe sea blue or light blue, but colors have been combined, separated, and redefined to offer colors such as Denim and Pacific Blue that are available in addition to the original blues.
The thought of having more disorders can also be applied to Autism. There are now many recognized versions of autism that are ordered along a spectrum that are all different in their own way. Although these differences may have existed long ago, they are becoming more frequently recognized now that there are clearer definitions of what each disorder actually entails. There is also increasing information about other disorders that keep autism from being characterized as these other disorders (such as childhood schizophrenia) like they might have been in the past. In conclusion, disorders and number of people with disorders is not increasing, but our classification systems and knowledge base of what constitutes each is increasing dramatically.
If there isn’t an epidemic, what could be happening?
there are some experts that say the increase in autism prevalence rates may be due to an increase in assortative mating by so called “geeks”. Autism is thought to be caused by more than one gene, and theoretically if two people mated that had a higher prevalence of the genes that could cause autism, that these genes would continue to be more and more common in these gene pools. There seems to be an increased amount of people with evident autistic characteristics in “geek” type professions such as computer science, technology, and engineering. Many autistics are drawn to these types of professions, especially if they have connections with computers. It is evident that it would be easier for a socially awkward person to feel more comfortable working on a computer all day instead of being emerged in a highly social work environment. If people in these groups exhibit more autistic traits than the general population, it is reasonable to think that they could have predisposing genes. However, this also does not mean that they absolutely do have “autistic genes,” and there is not data thus far to prove that they do or do not. Importantly, it is true that autistic parents do not always have an autistic child. However, it intuitively makes sense that a couple would be more likely to have an autistic child if both of them had marked autistic tendencies than if only one or neither did. Another point about this theory is the fact that many of these geeks that have autistic traits may actually have had autism when they were younger. If the parents are currently in their forties or fifties right now, they may not have had an opportunity to be diagnosed when they were young. Their autism could not only have brought them to their current field, but it could be an even stronger genetic link.
On the other hand, there are also many other reasons why we could be seeing the same increases in specific populations that have so many geeks. First, the people in a secluded gene pool could all be experiencing a similar environment. We know that autism has environmental influence because the twin concordance rate is not 100%; therefore environment must play some role in triggering genes. If people are in similar environments, they may experience the same triggers. We also realized that many of these geeks would reasonably be more educated that a random selection of the general population and also may have increased connections with science. Therefore, they may be more inclined to notice characteristics of autism as well as decide to take their child to the doctor for a diagnosis. We also thought that many of the people in this population would be more likely to be diagnosed with Asperger’s syndrome rather than full out autism. In less educated or lower SES populations, many children with Asperger’s may be more likely to not get diagnosed as their quirks could reasonably be attributed to other contributors when there is little known about the condition in these environments. We also determined that although gene interactions could be possible in this type of population, in order for gene interaction to be really prevalent, there has to be some evolutionary genetic forces occurring. With this in mind and the fact that evolution takes so long to emerge, it is doubtful that such a high increase in prevalence could be due to gene interactions in a secluded or specialized populations. More problematic is the fact that these geeks are not exclusively mating with other geeks, making it even more difficult for evolutionary genetics to step in.
In the end, although the hypothesis could be possible, there is insufficient evidence to prove the hypothesis. What is more important is that, if true, this could be contributing to the increased prevalence of autism, but it is not a major contributor of the increase. There are too many other factors that could very easily be influencing the high rate of autism found in certain areas.
Three Reasons Not to Believe in an Autism Epidemic- Morton Ann Gernsbacher, Michelle Dawson, and H.Hill Godsmith -http://www.autcom.org/pdf/Epidemic.pdf