Last edited 07/2022 and last reviewed 07/2022

  • autistic spectrum disorders (ASDs)
    • are estimated to affect approximately 1% of children (1,2)
      • however, using nationally representative data in the US, the estimated ASD prevalence was 3.14% among children and adolescents in the US in 2019 and 2020 (4)

    • are significantly skewed towards boys, with a sex ratio of 4:1 (1)

    • among siblings of children with an ASD, the prevalence increases to 2-8% (1)

    • concordance of autism in monozygotic twins is 36-60%, versus 0% in same sex dizygotic twins (1)

    • the heritability of ASDs has been estimated to be about 90%, making ASDs the most heritable of the childhood onset neuropsychiatric disorders(1)

    • core autism behaviours are typically present in early childhood, although some features may not manifest until a change of situation, for example, the start of nursery or school or, less commonly, the transition to secondary school. Regression or stasis of language and social behaviour is reported for at least a third of children with autism. This usually, but not exclusively, occurs between the ages of 1 and 2 years, and the reasons for regression and stasis are unknown (3)

    • around 70% of people with autism also meet diagnostic criteria for at least one other (often unrecognised) psychiatric disorder that further impairs psychosocial functioning, for example, attention deficit hyperactivity disorder (ADHD) or anxiety disorders (3)

    • intellectual disability (IQ below 70) coexists in approximately 50% of children and young people with autism (3)