The phrase “neurodevelopmental disabilities,” or “neurodevelopmental disorders,” refers to a group of conditions that appear early in one’s development (usually childhood) and lead to developmental deficits that impair various areas of functioning (personal, social, academic, and professional). The panel of limitations that arise from a neurodevelopmental disorder is very broad and ranges from difficulties in learning and controlling executive functions to general impairments of social skills or intelligence. 

     In this handbook, cognitive and behavioral symptoms of neurodevelopmental disabilities are mainly taken from the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). This document is a manual that aims to “define and classify mental disorders in order to improve diagnoses, treatment, and research” (American Psychiatric Association, 2021). Though it is an extensive resource, the DSM-5 has been criticized for its systematic and medical orientation in its presentation of various conditions. An alternative approach to mental conditions is through the framework of thinking that is the concept of neurodiversity. This term refers to the broad panel of variations in the human brain regarding various abilities. According to Baron-Cohen, this framework is based on the following three principles. (1) There is no ordinary brain; instead, there is a large range of variations in the brain from which arise different structures and abilities. (2) The language and concepts used to talk about disability should be non-stigmatizing to avoid conveying harmful and problematic stereotypes. (3) Disabilities should not be pathologized, and their positive outcomes should be as much considered as the negative ones (Baron-Cohen, 2017). Ultimately, these ideas lead to considering the variations of biological features, rather than being ruled out, as something to be integrated into our framework of thinking and, consequently, our societal system, deserving respect and acknowledgment as a form of diversity.