Epidemiology

• 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 skewed towards boys, with a sex ratio of 3:1 (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)

There are estimated to be around 52 million people living with ASD worldwide. (5)

Reference:

1. Hodges H, Fealko C, Soares N; Autism spectrum disorder: definition, epidemiology, causes, and clinical evaluation. Transl Pediatr. 2020 Feb;9(Suppl. 1)
2. NICE. Autism spectrum disorder in adults: diagnosis and management. Clinical guideline CG142. Published June 2012, last updated June 2021
3. NICE. Autism spectrum disorder in under 19s: support and management. Clinical guideline CG170. Published August 2013, last updated June 2021
4. Li Q, Li Y, Liu B, et al. Prevalence of Autism Spectrum Disorder Among Children and Adolescents in the United States from 2019 to 2020. JAMA Pediatr. Published online July 05, 2022. doi:10.1001/jamapediatrics.2022.1846
5. Baxter AJ, Brugha TS, Erskine HE, et al. The epidemiology and global burden of autism spectrum disorders. Psychol Med. 2015 Feb;45(3):601-13