What is autism?

The term "Autism spectrum disorder" (ASD), in vogue at present, has evolved after continual substantial developments taking place over more than a century. ASD is a heterogeneous, multi-factorial, developmental disability in which an unusual pattern of development takes place during infant and toddler years. As per DSM-5, Autism spectrum disorder is a combined phrase for a family of complex developmental disabilities inclusive of "Autistic Disorder, Pervasive Developmental Disorder not Otherwise Specified (PDD-NOS), and Asperger's Disorder". "ASD is characterized not only by persistent impairments in reciprocal social communication and social interactions, but is also manifested by restricted, repetitive patterns of behavior, interests, or activities". The classical clinical signs that exist in two major domains, viz. the 'social domain' and the 'behavioral domain' for the precise diagnosis of ASD have been tabulated and major differences between DSM-5 and DSM-4 are depicted with the help of a figure in this basic review article. A sharp rise in the incidence of ASD cases has been observed worldwide owing to various risk factors such as genetic predisposition coupled with adverse environmental conditions, gynecological interventions, etc. Two official manuals viz. the "Diagnostic and Statistical Manual of Mental Disorders" (DSM) (published by the American Psychiatric Association), and the "International Classification of Diseases" (ICD) (published by the World Health Organization) is being regularly updated to facilitate diagnosis of ASD. ICD-11 guidelines being prospectively implemented with effect from January 2022 have attracted global attention.