Chapter 8: Autism Spectrum Disorder
Autism spectrum disorder (ASD) is a developmental disorder that usually emerges within the first three years and persists throughout the individual’s life. There are three general categories of symptoms of ASD: presence of profound difficulties in social interactions and communication, combined with the presence of repetitive or restricted interests, cognitions, and behaviours. There is a wide variety of symptom combinations that may be present for people with ASD.
Previously, DSM-IV-TR included autism under a broader diagnostic category called Pervasive Developmental Disorders. Based on research and clinical experience, however, the separate disorders were collapsed into one diagnosis for DSM-5 (ASD).
In Canada, 1 in 66 children and youth (aged 5-17) are diagnosed with ASD, making it one of the most common developmental disorders. Males are four times more likely to receive a diagnosis of ASD.
Basic social perception is an important building block for more sophisticated social behaviours, like thinking about the emotions and motivations of others. Because of the social difficulties characterizing ASD, the functioning of the social brain is of great interest to autism researchers.
To date, the most investigated areas of the social brain in ASD are the superior temporal sulcus (STS), which underlies the perception and integration of biological motion, and the fusiform gyrus (FG), which supports face perception. Very early in life, children with ASD display reduced sensitive to biological motion and lack the attention to human faces that non-ASD infants possess.
Because of the many potential symptom combinations of ASD, identification of distinct (neurological) subgroups within the autism spectrum would allow for a more accurate and detailed exploration of individual differences between types of ASD.
It is particularly important to diagnose and treat ASD early in life. The lack of reliable predictors during the first year of life is an impediment to this early intervention. Treatment is often delayed for 2 or more years.