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Autism and Asperger’s: Two Distinct Disorders or One Disorder of Varying Symptom Severity

Autism has been conceptualized as a biologically determined set of behaviors occurring with varying presentation and severity that is likely as the result of varying cause (for review, see Goldstein, Naglieri, & Ozonoff, 2008). The disorder occurs significantly more often in boys (Smalley, Asernow, & Spence, 1988) and is found across all social classes (Gillberg & Schaumann, 1982). Recent surveys have suggested the incidence of autism in the general population may be as high as 1 per 113 (Center for Disease Control, 2007). Autism is a disorder in which individuals can present problems ranging from those that cause almost total impairment to others that allow the individual to function but not optimally. Children on the Autism Spectrum or continuum experience a wide range of developmental difficulties involving communication, socialization, thinking, cognitive skills, interests, activities and motor skills (Goldstein, Naglieri, & Ozonoff, 2008).

The Diagnostic and Statistical Manual IV – Text Revision (DSM-IV-TR) of the American Psychiatric Association (APA, 2000) criteria include a group of Pervasive Developmental Disorders under which Autism and Asperger’s are considered two distinct conditions. The criteria for Autistic Disorder include three sets of behavioral descriptions to qualify for the diagnosis. A child must show evidence of symptoms from at least two of the first set of criteria and one from each of the second and third sets of criteria. The first set of criteria features qualitative impairment and social interaction manifested by problems related to non-verbal behaviors including eye contact, facial expression, body posture and gestures of social interaction; failure to develop peer relationships appropriate to developmental level; markedly impaired sharing of emotional states or interests with others; expression of pleasure in other people’s happiness and a lack of social or emotional reciprocity. The second set of criteria must reflect a qualitative impairment in communication as manifested by a delay or total lack of the development of spoken language without efforts to compensate through gesture; marked impairments in the ability to initiate or sustain conversation despite adequate speech; repetitive or stereotyped use of language or idiosyncratic language; lack of varied, spontaneous, make believe play or social imitative play appropriate for the child’s developmental level. The third set of criteria involves repetitive and stereotypic patterns of behavior, restricted interests or activities including preoccupation in certain patterns of behavior that would be considered abnormal in intensity or focus; compulsive adherence to specific non-functional routines or rituals, repetitive motor mannerisms (self-stimulatory behavior), or persistent preoccupation with parts of objects. The second two sets of criteria include delay prior to the age of three in social interaction, language as used for social communication or symbolic, imaginative play.

Though considered a distinct disorder in the DSM-IV-TR, Asperger’s provides criteria identical to the Autism diagnosis for qualitative impairment in social interaction and restrictive, repetitive and stereotypic patterns of behavior. There is, however, no requirement for a qualitative impairment in communication. Specifically, this diagnosis requires an absence of clinically significant delay in language, acquiring single words by two years of age and communicative phrases used by three years of age. Because of the significant overlap in the diagnoses of these two conditions, most medical and mental health professions consider Asperger’s as a milder form of autism or even “high functioning autism” despite the fact that it is not delineated this way in the DSM-IV-TR. In fact, proposals for the Pervasive Developmental Disorder categories for DSM-V have recommended the elimination of the distinction between these two conditions and instead propose to refer to the combined conditions as Autism Spectrum Disorder (American Psychiatric Association, in press).

The new proposed diagnostic criteria contain four parts focusing on (1) social communication and social interaction, (2) restricted, repetitive patterns of behavior, interests and activities; (3) symptoms present in early childhood; and (4) symptoms that limit and impair everyday life. This approach suggests that the distinction between these two conditions is one of symptom severity rather than symptom type as first proposed by Goldstein and Naglieri (2009). As part of a standardization process for the Autism Spectrum Rating Scales (ASRS; Goldstein & Naglieri, 2009), we obtained approximately 6,000 protocols containing parent and teacher observational reports of children in the general population as well as those with specific developmental disorders such as Autism and Asperger’s and related conditions. Data were collected by 70 site coordinators throughout the United States and Canada. Efforts were made to guarantee that diagnoses were made in a standard fashion across all sites. As part of this process a group of children with a specific diagnosis of Asperger’s Disorder was collected. This study provided the opportunity to study the presence of autistic symptoms in a normative population of school children, as well as compare those diagnosed with Autism and Asperger’s.

The results of our study summarized in Figure 1 (see the ASRS Manual for more details about the methods and results) allows for a comparison between a group of children diagnosed with Autism and a group diagnosed with Asperger’s syndrome. The total ASRS score, three empirically derived scales, the DSM symptom score, and eight treatment scales containing behaviors specific to certain areas of functioning are shown. The ASRS T-scores are set to have a normative mean of 50 and a standard deviation of 10 based on a large representative sample of individuals in the US. Recall that a score of 60 falls at the 84th percentile and a score of 70 at the 98th percentile. As this instrument measures atypical or problematic behaviors, higher scores are indicative of greater number of symptoms.

Figure 1 provides a visual means of observing the differences between children with Autism and those with Asperger’s. As can be seen, the individuals with Autism and Asperger’s syndrome had nearly identical profiles which do differ on elevation. Figure 2 provides a comparison of each of the ASRS mean T-scores expressed as an effect size, that is, the difference between each mean expressed in standard deviation units. In addition to all of the differences being statistically significant (p < .01) the effect sizes ranged from a low of 0.43 (considered a small effect size) to 0.85 (considered a large effect size). The ASRS Total T-score effect size was 0.78. The largest difference was found for the ASRS Social/Communication scale. This is consistent with the current conceptualization of and diagnostic criteria for Asperger’s as a condition characterized by normal early language development. These findings strongly suggest that the difference Autism and Asperger’s syndrome is based on severity not a different composition of symptoms like, for example, the difference between individuals with Autism versus those with Attention Deficit Hyperactivity Disorder (see Goldstein & Naglieri, 2011).

Despite widely held belief over the past twenty years that youth with Asperger’s as a condition distinct from Autism have a better life outcome than those with Autism (Klin, Sparrow and Volkmar, 2000), the life course and adult outcome for youth currently diagnosed with Asperger’s may in fact be better than those with Autism simply because their symptom profile is milder and they develop functional language at a much earlier age, typically demonstrating the ability to use language to communicate despite pragmatic problems. At this time, these data strongly support the decision by the DSM-V committee to eliminate the Asperger’s and Pervasive Developmental Disorder – Not Otherwise Specified diagnoses and instead provide a single diagnosis of Autism Spectrum Disorder.

 

Sam Goldstein, PhD, is an Assistant Clinical Instructor in the University of Utah School of Medicine and Clinical Director of the Neurology at the Learning and Behavior Center. Jack A. Naglieri, PhD, is a Research Professor at the University of Virginia and Senior Research Scientist at the Devereux Center for Resilient Children. They are co-authors of the Autism Spectrum Rating Scale (2009), Assessment of Autism Spectrum Disorders (2008) and Interventions for Autism Spectrum Disorders (2012). Dr. Goldstein is also co-author of Raising Resilient Children with Autism Spectrum Disorders (2012).

 

References

 

American Psychiatric Association (APA) (2000). Diagnostic and statistical manual of mental disorders (4th ed. – text revision). Washington, DC: Author.

 

American Psychiatric Association (APA) (in Press). Diagnostic and statistical manual of mental disorders (5th Edition). Washington, DC: Author).

 

Center for Disease Control and Prevention (2007). Prevalence of the autism spectrum disorders in multiple areas of the United States, Surveillance Years 2000 and 2002: A report from the Autism and Developmental Disabilities Monitoring (ADDM) Network (February 8, 2007). Atlanta, Georgia: Author.

 

Gillberg, C., & Schaumann, H. (1982). Social class and autism: Total population aspects. Journal of Autism and Developmental Disorders, 12, 223-228

 

Goldstein, S. & Naglieri J. (2011). Neurocognitive and Behavioral Characteristics of Children With ADHD and Autism. ADHD Report, 19, 10-12.

 

Goldstein, S., Naglieri, J. (2009). Autism Spectrum Rating Scales – Technical Manual. North Tonawanda, Canada:  Multi-Health Systems.

 

Goldstein, S., Naglieri, J., & Ozonoff, S. (Eds.) (2008). Assessment of Autism. New York, NY: Guilford Press.

 

Klin, A., Volkmar, F.R., & Sparrow, S.S. (2000). Asperger Syndrome. New York, NY: Guilford.

 

Smalley, S., Asarnow, R., & Spence, M. (1988). Autism and genetics: A decade of research. Archives of General Psychiatry, 45, 953-961.

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  1. […] what was then referred to as Asperger’s syndrome and would now be considered autism because Asperger’s syndrome is no longer considered distinct from autism. But I think she always had an image of me – or wanted a child – who was fairly what […]

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