Autism spectrum disorder: characteristics, diagnosis, and treatment approaches

¶ … Kogan et al. (2009) report that the increasing prevalence of autistic spectrum disorders (ASDs) makes the identification of these disorders a public health priority. Many of the studies of the prevalence of ASD are taken from clinical data; the researchers believe that this data inaccurate. The researchers review all of the current research used to determine the prevalence of ASD and point out several flaws in each of these studies. In order to get an accurate point prevalence measurement the researchers used the National Survey of Children's Health (N = 78, 037) that utilizes parental reports of children aged three to seventeen years old to determine the prevalence of ASD. The study would help identify demographic variables associated with ASDs.

The researchers considered a child in the study to have ASD if a physician had told their parents at one time or another that the child had an ASD diagnosis. The results indicated that the prevalence of ASDs in U.S. children was 110 per 10,000 children. This estimate is significantly higher than previous research has suggested. Demographic factors associated with an ASD diagnoses were also investigated. Boys were four times more likely than girls to have an ASD diagnosis, children living in the Midwest and Northeast were slightly more likely to have an ASD diagnosis, there was in effect for social economic status with lower social economic status families more likely to have an ASD child, and a mild effect for ethnicity. Interestingly, a significant proportion of children earlier diagnosed with ASD were reported by their parents as no longer having an ASD. This raises some diagnostic questions regarding how these disorders are diagnosed by physicians because if an ASD is a neurological condition the child should not be able to "grow out of it." Nonetheless, the researchers totally missed the boat on this particular article. The increase in the prevalence of diagnosed ASD's in the United States is more due to the changes in the diagnostic criteria in the DSM series than due to an actual increase in the prevalence of this disorders. This also explains why some children diagnosed with an ASD later no longer have it.

Oberman and Ramachandran (2007) discuss ability of humans to understand the actions or internal states of others relies on both the ability of the observer to perceive other people as being like them and to be able to simulate these actions of within one's own internal representations. These simulation theories contain four different basic contexts: people and objects, actions and body, states, introspective states, and settings. Theories of this nature carry more weight when they are able to identify or hypothesize the neuro-anatomical features associated with the system. One such system receiving much attention over the last years is been the mirror neuron system (MNS). The researchers then trace the history of both simulation theories and the MNS in animal models and research identifying potential brain areas where such a MNS has been tentatively identified in humans (most of the studies are experimental studies using neuroimaging techniques). The literature review is quite complete and impressive.

A hallmark of ADS is a lack of empathy or theory of mind (TOM) universally observed in affected individuals. The researchers thoroughly discuss TOM and its relation to socialization, language learning, intelligence, and other cognitive capacities. They draw heavily on the diagnostic criteria for autism which indicates that the affected individual has difficulty learning expressive language and how a TOM is important in learning by imitation. The subsequent conclusion is that autistics spectrum disorders may be characterized by a dysfunction in the MNS and it is this dysfunction that accounts for the presentation of ASDs in humans. The theoretical premise for this hypothesis is actually quite well developed; however, actual MNS has not been conclusively identified in humans. However, as the researchers demonstrate the predictions made by this theory (e.g., dysfunctions in the proposed MNS systems and humans would be noted in autistic individuals) are not always confirmed. However, this review is quite complete and extensive and does propose an interesting theory on the etiology of ASDs.

In a related study Dawson et al. (2009) site previous research that has suggested that the head circumference of children with an ASD (specifically in this case autism) can be identified after their second year by their decreased head circumference. Dawson et al. were interested in confirming if this was an actual measurable difference. They followed 28 children (17 children with autistic disorder and 11 children with pervasive developmental disorder NOS) over a three-year period. The children were predominantly male and Caucasian. Head circumference measurements were taken from medical records of the occipital -- frontal circumference which is considered to be a good measure of brain volume and children their lesson seven years old. Every child in the sample had at least three valid measurements over the course of the study and the mean number of head circumference measurements was seven. Height and weight data were also included in the study to make sure that any head circumference measurements could be compared to body size.