Autism spectrum disorder (ASD) refers to a neurodevelopment disorder that is characterized by difficulties with social communication and social interaction and restricted and repetitive patterns in behaviors, interests, and activities. By definition, the symptoms are present early on in development and affect daily functioning. The term ‘spectrum’ is used because of the heterogeneity in the presentation and severity of ASD symptoms, as well as in the skills and level of functioning of individuals who have ASD.

ASD occurs in all racial and ethnic groups, and across every socioeconomic status level. Boys are about four times more likely to have ASD than girls. According to the Centers for Disease Control and Prevention, it is estimated that 1 in 59 children meets criteria for ASD. Because it is hoped that early intervention can change the course of ASD, immediate response in terms of provision of treatment is critical when there are early concerns (even under 24 months).