Individuals with ASD also display substantial variation in the presentation of sensory abnormalities. ‘Insistence on sameness’ behaviors also seem to be independent of autism symptom severity, age, and intelligence quotient (IQ), suggesting that it may be a useful qualitative characteristic by which to identify ASD subtypes. With respect to the quality of symptoms, there is some evidence to suggest that ‘insistence on sameness’ behaviors are distinct from other core ASD features and from symptoms of anxiety. For example, results from a longitudinal study suggested that RRB quantity at 2 years of age is inversely related to language skills at 9 years. Some individuals with ASD have unique patterns of social-communication deficits and RRBs, suggesting a possible avenue by which ASD subgroups might be defined. Second, DSM-5 formally recognizes many features that are not specific to ASD by which researchers can qualify ASD diagnoses. First, although DSM-5 requires that symptoms from both the RRB and social-communication domains are present, it allows individual variation in the quality and quantity of specific RRBs and social-communication deficits. In addition, DSM-5 introduces a dimensional approach that allows researchers to capture variability within samples in two important ways. The emphasis on specificity in the DSM-5 improves researchers’ ability to identify samples of interest. Other DSM-IV symptoms have been retained in DSM-5, but their definition has been revised in order to increase specificity. One feature of unusual communication, stereotyped language, has been reassigned to the RRB domain to reflect results from factor analytic studies. DSM-5 includes unusual sensory responses in the RRB domain to reflect research showing that these behaviors are prevalent in ASD and are useful in distinguishing ASD from other disorders. In addition, although the criteria for DSM-IV Autistic Disorder required a delay in or complete lack of development in expressive language, this requirement has been eliminated in DSM-5 because research has shown that this characteristic is neither specific nor universal to individuals with ASD.Ĭhanges within symptom domains have also been warranted. Over the past two decades, an increase in access to large and diverse samples has given researchers the ability to determine that, in many cases, ASD symptoms are best represented in a two-domain model of social-communication deficits and restricted and repetitive interests/behaviors (RRB), rather than by the DSM-IV triad of symptoms that models communication deficits separate from social impairments. Less publicized were the content changes and the new symptom structure in DSM-5. The change in DSM-5 that received the most media attention is the removal of the DSM-IV clinical subtypes. found that over 90% of children with DSM-IV-defined PDDs were identified by DSM-5 criteria, and the specificity using the new diagnostic criteria was substantially improved compared with the DSM-IV criteria. Consequently, the fifth edition of the DSM (DSM-5) replaces the multi-categorical system with a single diagnostic dimension: ASD.Īlthough concerns have been raised about the validity and diagnostic sensitivity of the proposed DSM-5 criteria, a number of studies have emerged in support of the conceptual validity of the new criteria. A number of studies have reported limited reliability in how DSM-IV subtypes are assigned, with similar core symptom presentations across the categorical diagnoses and poor predictive ability of later outcome based on these subtypes. The Diagnostic and Statistical Manual of Mental Disorders, 4 th edition (DSM-IV) used a multi-categorical system of diagnosing pervasive developmental disorders (PDDs), which included autistic disorder, Asperger’s disorder, pervasive developmental disorder not otherwise specified, childhood disintegrative disorder, and Rett’s disorder, that created challenges to this effort. This effort has been largely unsuccessful because distinct, empirically defined subgroups have yet to be reliably identified. Over the past several decades, researchers have attempted to categorize the heterogeneity in autism spectrum disorders (ASDs).
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