The deletion of Asperger’s disorder (Asperger's syndrome) as a separate diagnostic category from the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) has been widely publicized. The new DSM-5 category of autism spectrum disorder(ASD), which subsumes the previous DSM-IV diagnoses of autistic disorder (autism), Asperger’s disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS), reflects the scientific consensus that symptoms of the various DSM-IV subgroups represent a single continuum of impairment that varies in level of severity and need for support.
An important feature of the DSM-5 criteria for ASD is a change from three symptom domains (triad) of social impairment, communication deficits and repetitive/restricted behaviors, interests, or activities to two domains (dyad); social/communication deficits and fixated and repetitive pattern of behaviors. Several social/communication criteria were merged to clarify diagnostic requirements and reflect research indicating that language deficits are neither universal in ASD, nor should they be considered as a defining feature of the diagnosis. The criteria also feature dimensions of severity that include current levels of language and intellectual functioning as well as greater flexibility in the criteria for age of onset and addition of symptoms not previously included in the DSM-IV such as sensory interests and aversions.
DSM-IV Criteria in Practice
Problems in applying the DSM-IV criteria were a key consideration in the decision to delete Asperger’s disorder as a separate diagnostic entity. Numerous studies indicate that it is difficult to reliably distinguish between Asperger syndrome, autism, and other disorders on the spectrum in clinical practice (Attwood, 2006; Macintosh & Dissanayake, 2006; Leekam, Libby, Wing, Gould & Gillberg, 2000; Mayes & Calhoun, 2003; Mayes, Calhoun, & Crites, 2001; Miller & Ozonoff, 2000; Ozonoff, Dawson, & McPartland, 2002; Witwer & Lecavalier, 2008). For example, children with autism who develop proficient language have very similar trajectories and later outcomes as children with Asperger disorder (Bennett et al., 2008; Howlin, 2003; Szatmari et al., 2000) and the two are indistinguishable by school-age (Macintosh & Dissanayake, 2004), adolescence (Eisenmajer, Prior, Leekam, Wing, Ong, Gould & Welham 1998; Ozonoff, South and Miller 2000) and adulthood (Howlin, 2003). Individuals with Asperger disorder also typically meet the DSM-IV communication criterion of autism, “marked impairment in the ability to initiate or sustain a conversation with others,” making it is possible for someone who meets the criteria for Asperger’s disorder to also meet the criteria for autistic disorder.
Treatment and Outcome
Another important consideration was response to treatment. Intervention research cannot predict, at the present time, which particular intervention approach works best with which individual. Likewise, data is not available on the differential responsiveness of children with Asperger’s disorder and high-functioning autism to specific interventions (Carpenter, Soorya, & Halpern, 2009). There are no empirical studies demonstrating the need for different treatments or different responses to the same treatment, and in clinical practice the same interventions are typically offered for both autism and Asperger’s disorder (Wilkinson, 2010). Treatments for impairments in pragmatic (social) language and social skills are the same for both groups.
Application of the New Criteria
It’s important to remember that in the DSM, a mental disorder is conceptualized as a clinically important collection of behavioral and psychological symptoms that causes an individual distress, disability or impairment. The objective of new DSM-5 criteria for ASD is that every individual who has significant “impairment” in social-communication and restricted and repetitive behavior or interests should meet the diagnostic criteria for ASD. Because language impairment/delay is not a necessary criterion for diagnosis, anyone who demonstrates severe and sustained impairments in social skills and restricted, repetitive patterns of behavior, interests, or activities in the presence of generally age-appropriate language acquisition and cognitive functioning, who might previously have been given a diagnosis of Asperger’s disorder, will now meet the criteria for ASD.
The new DSM-5 criteria for ASD have created significant controversy over concerns that it would exclude many individuals currently diagnosed with Asperger syndrome and PDD-NOS, and thus make it difficult for them to access services. However, recently published field trials suggest that the revisions actually increase the reliability of diagnosis, while identifying the large majority of those who would have been diagnosed under the DSM-IV-TR. Of the small numbers who were not included, most received the new diagnosis of “social communication disorder.” Moreover, the accuracy of non-spectrum classification (specificity) made by DSM-5 was better than that of DSM-IV, indicating greater effectiveness in distinguishing ASD from non-spectrum disorders such as language disorders, intellectual disability, attention-deficit/hyperactivity disorder (ADHD), and anxiety disorders. It is also important to note that all individuals who have a DSM-IV diagnosis on the autism spectrum, including those with Asperger syndrome and PDD-NOS, will be able to retain an ASD diagnosis. This means that no one should “lose” their diagnosis because of the changes in diagnostic criteria. According to DSM-5, individuals with a well-established DSM-IV diagnosis of Autistic Disorder, Asperger’s Disorder, or PDD-NOS should be given a diagnosis of ASD. Those who have marked deficits in social communication, but whose symptoms do not meet the criteria for ASD, should be evaluated for Social (Pragmatic) Communication Disorder.
In conclusion, the DSM-5 category of autism spectrum disorder (ASD), which subsumes the current diagnoses of autistic disorder, Asperger’s disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS), better describes our current understanding about the clinical presentation and course of the neurodevelopmental disorders. Conceptualizing autism as a spectrum condition rather than a categorical diagnostic entity is in keeping with the extant research suggesting that there is no clear evidence that Asperger’s disorder and high-functioning autism are different disorders. As Gillberg (2001) notes, the terms Asperger's syndrome and high-functioning autism are more likely “synonyms” than labels for different disorders. Lord (2011) also comments that although there has been much controversy about whether there should be separate diagnoses, "Most of the research has suggested that Asperger's syndrome really isn't different from other autism spectrum disorders." "The take-home message is that there really should be just a general category of autism spectrum disorder, and then clinicians should be able to describe a child's severity on these separate dimensions." Unfortunately, many individuals may have been advised (or assumed) that a diagnosis of Asperger’s disorder was separate and distinct from autistic disorder and that intervention/treatment, course, and outcome were clinically different for each disorder. While including Asperger’s Disorder under the DSM-5 category of ASD will likely continue to require a period of transition and adjustment, the proposed dimensional approach to diagnosis will likely result in more effective identification, treatment, and research for individuals on the spectrum.