This perspective article compares and contrasts the conceptualization of Autism Spectrum Disorder (ASD) in ICD-11 and DSM-5. By guiding the user through the ICD-11 text, it is argued that, in contrast to DSM-5, ICD-11 allows a high variety in symptom combinations, which results in an operationalization of ASD that is in favor of an extreme diverse picture, yet possibly at the expense of precision, including unforeseeable effects on clinical practice, care, and research. The clinical utility is questionable as this conceptualization can hardly be differentiated from other mental disorders and autism-like traits. It moves away from an observable, behavioral, and neurodevelopmental disorder to a disorder of inner experience that can hardly be measured objectively. It contains many vague and subjective concepts that lead to non-falsifiable diagnoses. This bears a large danger of false positive diagnoses, of further increased prevalence rates, limitations of access to ASD-specific services and of increasing the non-specificity of treatments. For research, the hypothesis is that the specificity of ASD will be reduced and this will additional increase the already high heterogeneity with the effect that replication of studies will be hampered. This could limit our understanding of etiology and biological pathways of ASD and bears the risk that precision medicine, i.e., a targeted approach for individual treatment strategies based on precise diagnostic markers, is more far from becoming reality. Thus, a more precise, quantitative description and more objective measurement of symptoms are suggested that define the clinical ASD phenotype. Identification of core ASD subtypes/endophenotypes and a precise description of symptoms is the necessary next step to advance diagnostic classification systems. Therefore, employing a more finely grained, objective, clinical symptom characterization which is more relatable to neurobehavioral concepts is of central significance.

The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), is the 2013 update to the Diagnostic and Statistical Manual of Mental Disorders, the taxonomic and diagnostic tool published by the American Psychiatric Association (APA). In 2022, a revised version (DSM-5-TR) was published. In the United States, the DSM serves as the principal authority for psychiatric diagnoses. Tr T… "Mental retardation" was renamed "intellectual disability (intellectual developmental disorder)". Speech or language disorders are now called communication disorders—which include language disorder (formerly expressive language disorder and mixed receptive-expressive language disorder), speech sound disorder (formerly phonological disorder), childhood-onset fluency disorder (stuttering), and a new condition characterized by impaired social verbal and nonverbal communication called social (pragmatic) communication disorder. Autism spectrum disorder (ASD) is a new diagnosis that incorporates the former diagnoses of classic autism, Asperger disorder, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS). The DSM-5 organizes the symptoms of ASD into two groups: impaired social communication and/or interaction, and restricted and/or repetitive behaviors. The DSM-5 assigns three "severity levels" for ASD, with people in level 1 "requiring support", level 2 "requiring substantial support", and level 3 "requiring very substantial support". The updated classification under ASD reflects a dimensional approach, allowing clinicians to rate symptom severity instead of fitting patients into narrowly defined categories. This change also aimed to simplify diagnosis and improve access to services. Attention deficit hyperactivity disorder (ADHD) no longer specifies autism as an exclusionary diagnosis. The requisite age of symptom onset was changed from…

DSM-5 has moved autism from the level of subgroups (“apples and oranges") to the prototypical level (“fruit"). But making progress in research, and ultimately improving clinical practice, will require identifying subgroups within the autism spectrum.