Autism spectrum disorder

Last reviewed: 26 Apr 2022
Last updated: 19 May 2021



History and exam

Key diagnostic factors

  • presence of risk factors
  • language delay or regression
  • verbal and non-verbal communication impairment
  • social impairment
  • repetitive, rigid, or stereotyped interests, behaviour, or activities
More key diagnostic factors

Other diagnostic factors

  • placid or very irritable as a baby
  • feeding difficulties
  • unusual posturing
  • motor stereotypies
  • sensory interests or difficulties
  • evidence of other neurodevelopmental disorder
  • macrocephaly
Other diagnostic factors

Risk factors

  • male sex
  • positive family history
  • gestational valproate exposure
  • genetic variants
  • karyotype (chromosomal) abnormalities
  • increasing parental age
  • prematurity
More risk factors

Diagnostic investigations

1st investigations to order

  • ASD screening tests
  • Childhood Autism Rating Scale (CARS)
  • Modified Checklist for Autism in Toddlers (M-CHAT)
  • Childhood Autism Screening Test (CAST)
More 1st investigations to order

Investigations to consider

  • diagnostic questionnaires (e.g., Autism Diagnostic Interview-Revised [ADI-R]; Developmental, Dimensional, and Diagnostic Interview [3di]; Diagnostic Interview for Social and Communication Disorders [DISCO])
  • Autism Diagnostic Observational Schedule (ADOS)
  • skin examination with Wood light
  • genetic testing
  • EEG
  • MRI brain
  • audiology
  • specific testing for genetic disorders (e.g., MECP2 deletion)
More investigations to consider

Treatment algorithm


pre-school children aged 12 months to 5 years (or equivalent developmental age)

school-age children aged 5 to 18 years (or equivalent developmental age)




Jeremy Parr, MB ChB, MRCPCH, MD

Professor/Honorary Consultant

Population Health Sciences Institute

Newcastle University

Newcastle upon Tyne



JP is a director and shareholder in XRTherapeutics, which offers virtual reality intervention for situation specific anxiety and phobia for people with autism and other conditions. He is named on a patent owned by Third Eye Neurotech and would receive royalties from this, through Newcastle University. JP previously chaired Research Autism's Scientific Advisory Committee; was an expert advisor to the National Autism Project; sits on the Autistica Discover Steering Committee; currently chairs the Autistica Physical Health and Ageing Research Group; and currently chairs the British Academy of Childhood Disability Strategic Research Group. He has not received payment for any of this activity. JP works for the UK NHS and sees children and young adults on the autism spectrum to give advice about diagnosis and treatments/interventions. JP runs research programmes focused on autism from Newcastle University, and has received grants and published research papers in that context. JP is an author of a number of references cited in this topic.

Marc Woodbury-Smith, MB ChB, PhD, MRCPsych
Marc Woodbury-Smith

Clinical Senior Lecturer/Honorary Consultant

Biosciences Institute

Newcastle University

Newcastle upon Tyne


Associate Investigator

Centre for Applied Genomics

Hospital for Sick Children




MWS has received consultation fees from Servier Pharmaceuticals in connection with a clinical trial on which he was national co-ordinator (2018-2019). MWS is the co-author of references cited in this topic.

Peer reviewers

Michael Craig, MBBS,​ BSc(Hons), PhD, FRCOG, FRCPsych

Senior Lecturer & Honorary Consultant

Department of Forensic and Neurodevelopmental Sciences

Institute of Psychiatry

De Crespigny Park




MC declares that he has no competing interests.

Kevin Sanders, MD

Associate Clinical Professor of Psychiatry and Pediatrics

Vanderbilt Department of Psychiatry




KS declares that he has no competing interests.

  • Differentials

    • Other causes of disordered development/learning difficulties/intellectual disability, or another neurodevelopmental disorder
    • ADHD
    • Social (pragmatic) communication disorder
    More Differentials
  • Guidelines

    • Autism spectrum disorder in adults: diagnosis and management
    • Autism spectrum disorder in under 19s: support and management
    More Guidelines
  • Patient leaflets

    Autism spectrum disorder: information for parents - What is autism spectrum disorder?

    Autism spectrum disorder: information for parents - What treatments work?

    More Patient leaflets
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