Autism Spectrum Disorder



Autism Spectrum Disorder





BACKGROUND

Leo Kanner’s (1943) first explicit description of the syndrome of early infantile autism remains a “classic.” He described 11 children who had two common features: “autism” (living in one’s own world cut off from others) and “insistence on sameness”—a term that included literal resistance to change. The latter term encompassed, to his way of thinking, some of the repetitive behaviors that he saw as the child’s attempt to “maintain sameness” in the environment. His paper also mentioned many of the clinical features we see today, for example, echolalia (speech repetition), difficulties with communication including for some a total absence of spoken language. He noted that he believed the condition to be of very early onset and emphasized the lack of unusual facial features, that is, like those of children with trisomy 21. He also noted some areas of apparent strength in nonverbal tasks like puzzles.

A year after Hans Asperger (1944), a Viennese medical student also used the term autism to describe what he viewed as more a personality problem than a developmental disorder. His small group of cases, all boys, had difficulties in joining groups partly because of their major and intrusive circumscribed interests. The latter could include more typical interests (rocks, dinosaurs) or more esoteric ones (train schedules, American gangsters), and, in addition to complicating peer interaction, the family often found its life revolved around the interest. Asperger made the important point of noting how these interests interfered with the child’s acquisition of other skills.

Effectively, these two clinical descriptions (of Kanner and Asperger), while differing in important respects, set the tension that exists today between narrow and broad views of autism, and the autism spectrum differed in many respects but did have an important point of connection: the emphasis of problems of social engagement. The debate between broad and narrow views of autism and related conditions is ongoing and is now part of a broader discussion of neurodiversity and what has been termed the broader autism phenotype (Ingersoll & Wainer, 2014).

In retrospect, children with something very similar to autism existed well before this description. It is quite possible that reports of so-called feral or wild children (presumed to have been reared by animals) represented the first known cases of the condition. Children who we would now likely say had autism were also noted in the 1800s as suggested by case records kept at training schools for the intellectually impaired.

Research on the conditions was slow to develop for many years. This reflected several factors. Kanner’s use of the term autism had suggested to many a source of connection with schizophrenia, and childhood schizophrenia, although we now recognize that schizophrenia
in children is vanishingly rare (see Chapter 15). Other sources of confusion arose given Kanner’s early impression that children with autism did not have overall intellectual deficiency (mental retardation)—this impression reflected their often good abilities with nonverbal tasks. As time went on, it became clear that unusual IQ profiles were seen with strengths in nonverbal areas and major weaknesses in verbal ones, with older children often scoring in the intellectually deficient range. Psychoanalytic theorizing at the time autism was first described speculated that some parent-child interaction issues led to autism—a notion that led to years of unproductive psychotherapy for parents and children alike. Several key findings in the 1970s established the validity of autism and underscored the need for its official recognition: (1) autism differed from childhood schizophrenia in many; (2) autism was brain based and strongly genetic; and (3) children with autism responded better to structured teaching than unstructured psychotherapy.


DIAGNOSIS, DEFINITION, CLINICAL FEATURES

The growing awareness that autism was a distinctive condition led to new efforts to provide better guidelines to diagnosis. These included Rutter’s (1978) synthesis of Kanner’s original paper with subsequent research and the earlier efforts to provide a diagnostic checklist. The decision was made to include autism in the groundbreaking third edition of the DSM.

The DSM-III (APA, 1980) definition fostered what became an explosion of research work on autism. This definition of “infantile autism” was included in a new class of disorder—pervasive developmental disorder (PDD). The problem with DSM-II was its lack of developmental orientation; this was rectified in the DSM-III-R (APA, 1987) that provided a more flexible, polythetic approach to the diagnosis of “autistic disorder.” Issues with this definition were addressed in the major revision of DSM-IV (1990), which included a field trial conducted in conjunction with the ICD-10 revision. This field trial led to the convergence of ICD-10 and DSM-IV for autism—a factor that further enhanced research and also fostered the development of new dimensional approaches to diagnosis. This approach to diagnosis also included several other conditions including Asperger’s disorder, Rett syndrome, and childhood disintegrative disorder as well as a “subthreshold” category (termed PDD-NOS [not otherwise specified] in DSM and atypical autism in ICD-10) for cases not quite meeting the full criteria for autism. The definition proposed for autism included a total of 12 criteria grouped across three categories of social interaction problem, communication/play criteria, and restricted interest and repetitive behavior. Under this system, there were over 2200 ways to attain a diagnosis of autism using the provided criteria. It remained the gold standard for nearly two decades.

There were a number of differences in the overall DSM-5 (APA, 2013) approach to diagnosis, some of which proved controversial for autism; rather than conducting a large field trial, a large set of dimensional diagnostic data derived from assessments were analyzed. The number of criteria was reduced with a combination of monothetic (for symptom areas, all criteria were needed) and polythetic (for the other symptom areas, only some were needed). As a result, the number of potential ways to achieve a diagnosis of autism was vastly reduced. Although the analysis of the large data set had many merits and of itself showed good sensitivity and specificity, criticisms quickly appeared (even before DSM-5 was published) that suggested a major change and narrowing of the diagnostic concept. In the new DSM-5 approach, Asperger’s disorder and PDD-NOS were eliminated, and only a small number (10% or so) of these cases would now achieve a diagnosis of ASD. Even for higher cognitive functioning autism, a substantial number of cases lost their diagnosis (MC Partland et al., 2012). In the United States, in particular, this had dramatic implications for service eligibility, and as a result, a decision was made near the end of the DSM-5 process to “grandfather in” cases with well-established previous diagnosis of autism, Asperger’s, and so forth. Effectively, this created a new system while perpetuating the old one! Thus, previous diagnostic terms like Asperger’s disorder remain in use.

A number of studies have now confirmed this problem both for the higher functioning older individuals and younger children (Smith, 2015). On the other hand, a major advance was the
name change of the overall category to autism spectrum disorder (ASD, somewhat paradoxically termed given the more restricted diagnostic concept), but this term is more consistent with the growing awareness of the range of genetic contributions to autism and the “broader autistic phenotype.” Perhaps in part concerned with just this awareness, a new social communication disorder (SCD) was added to the Communication Disorders section although it does not exactly converge either with the older concept of Asperger’s or atypical autism/PDD-NOS (it emphasizes problems in social communication leaving out restricted interests and repetitive behaviors). Table 7.1 summarizes the history of categorical definitions of autism.

The development of a number (now over 30) of screening and diagnostic instruments has been an important advance (Lord et al., 2014). These approaches have some important advantages over categorical ones. Some are designed more as screeners, others for use in schools and educational settings, and yet others as a part of more comprehensive diagnostic assessments. It is important to realize that some of these instruments require extensive training, because some of the more widely used screening instrument studies in large populations have been disappointing and important issues of gender and possible bias have been noted.


EPIDEMIOLOGY AND DEMOGRAPHICS

The earliest studies of the epidemiology suggested that it was a rather rare condition on the order of 1-2 cases/1000 children, but more recent studies suggest much higher rates on the order of 1 case/145 children (Meyers et al., 2019). Several factors appear to account for this
apparent change in rate. There are many challenges in terms of case identification, definition, sample size and methods, and so forth. Epidemiologic surveys of ASDs pose substantial challenges to researchers seeking to measure rates of ASD, particularly given the range of case definition, case identification, and case evaluation methods employed across surveys. As Fombonne and colleagues emphasize (Meyers et al., 2019), this current increase in prevalence cannot be directly attributed to actual changes in incidence of the disorder. There is fairly good evidence to suggest that a number of factors have led to changes in rates—these include changes in educational policy (i.e., inclusion of special needs children in public schools in the United States), changes in diagnostic criteria, and the marked increase in awareness of ASD in the general population as well as on the part of some parents, and the desire to have this label to increase special educational services provided. Indeed, the expansion in cases diagnosed in developed countries has risen in parallel with the growing availability of effective treatment programs. The major difficulties of undertaking good epidemiologic studies must be noted, that is, in methods of case assessment and sizes of samples. In small samples, rates are notoriously more variable. As noted earlier, the recent changes in DSM-5 may tend to lower identified cases.








There is an apparent male predominance (at least 3-5 times more common), although this is much less pronounced in lower IQ groups and much more pronounced in high IQ cases. However, it is possible that subtle gender differences impact case identification and lead to underdiagnosis in girls. It does appear that, with usual diagnostic criteria and approaches, there is a marked male predooming in the normal range of cognitive ability—perhaps 25 or more to 1.

Cultural and ethnic issues may impact treatment and, to some extent, case detection of autism generally is remarkably similar around the world (Freeth et al., 2014). There is a growing awareness of the need for diagnosis and intervention in third world countries. The early impression that autism was more likely in children of parents with more education and higher occupational status clearly proved incorrect.


ETIOLOGY AND PATHOGENESIS

As noted previously, early speculation centered on psychodynamic explanations of autism. The growing body of evidence in the 1970s that autism was brain based and highly genetic changed to focus of work on the pathogenesis of the condition markedly.

A major effort has been on understanding the “autism” in autism, that is, the social brain connection (see Table 7.2). This research has centered on a number of specific brain regions that appear to be basic to understanding social information (McPartland et al., 2014).

Regions involved include the amygdala, the orbitofrontal cortex, and the ventral and lateral temporal cortexes, and supporting data have come from work in nonhuman primate electrophysiology and human neuropsychology. This work has also led to a now great volume of work on neuroimaging, particularly with fMRI and EEG processing of faces and social information (e.g., biologic movement). Well-replicated work using fMRI has shown differences in processing of the face in the fusiform facial recognition area gyrus. Similarly, work with EEG has shown differences in face processing use evoked potential and this finding may emerge as the first generally recognized biomarker of autism. Working using eye-tracking paradigms has shown marked differences in the way persons with autism view social situations—often paying less attention to the more affectively rich upper portion of the face (Figure 7.1).

The study of genetic factors in autism has similarly advanced and a number of important findings have emerged. These include the association of autism with some well-recognized genetic disorder, for example, fragile X and tuberous scleroses. Initially, it was hoped that the number of possible genes identified would be small, but this is not the case. In many ways, this finding is quite consistent with the recognition of a “broader autism phenotype.” A number of candidate genes have now been identified and many of these have important functions in the brain (Yuen et al., 2019). Advances in genetic testing have also made it easier to run a broad array of genetic assays in the individual case, and perhaps 10 to 20% of cases can now be associated with some genetic finding (although sometimes of unknown etiologic significance). Family studies have also shown a strong connection of autism in the child to other conditions in family members, for example, anxiety problems and attention difficulties.
Thus, it is increasingly clear that ASDs are a collection of highly heterogeneous conditions with, perhaps, one or more final common pathways to clinical expression. With increasingly sophisticated genetic studies, it is likely that more such specific pathways will be identified. There clearly is the potential impact of some environmental factor or factors in this complex process, although to date it is the genetic factors that appear to be most robustly elucidated.







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Jun 19, 2022 | Posted by in PSYCHOLOGY | Comments Off on Autism Spectrum Disorder
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