Autism spectrum disorder

Autism spectrum disorder (ASD) is an early onset and persistent condition defined by alterations in social communication and social interation alongside repetitive, restricted stereotypic behaviours and interests causing disabilities. Until recently, research on the co-occurrence of ADHD with ASD has been limited by DSM-IV criteria, allowing no dual diagnosis of these two neurodevelopmental disorders. Since the DSM-5 permits a double diagnosis of ADHD plus ASD, research on their comorbidity has substantially increased. In addition to shared and distinct aetiological factors, studies have revealed a high clinical impact of the combined symptomatology on individual outcomes. This chapter provides a selective overview of behavioural, cognitive, and biological findings as well as intervention strategies in combined ADHD/ASD phenotypes.