Genetic Disorders and Dual Diagnosis: Building Clinical Management on Etiology and Neurocognition

Major advances have been made in the identification of genetic neurodevelopmental disorders and psychological (dis)functioning among persons with intellectual disabilities. This chapter first provides an overview of developments on the topic. Thereafter, our preference to study “dual diagnosis” from a neuropsychological perspective is described, building upon the increasing opportunities in genetic testing and beyond classificatory diagnosis of psychiatric conditions (e.g., DSM, ICD) in genetic neurodevelopmental disorders. This implies a multimethod assessment of cognitive functioning and understanding behavior from a contextual perspective, across the life span. Applying this neuropsychological clinical research strategy provides opportunities for developing and implementing (multidisciplinary) treatment strategies, as is shown in the syndrome descriptions in Chap. 4. Common conditions such as Fragile X syndrome and Noonan syndrome are reviewed as well as several rare genetic syndromes (e.g., Kleefstra syndrome, KBG syndrome, and Phelan-McDermid syndrome) with typically co-occurring mental health disorders and/or challenging behaviors. Special attention is paid to Prader-Willi syndrome, because it typically illustrates the complex interplay of the syndrome-bound phenomena and the great benefits of interdisciplinary study thereof. Resulting clinical strategies that may emerge from the advocated genetic neuropsychological paradigm are shortly addressed, including future vistas on this dynamic and rapidly developing field.