Autism spectrum disorder

Last reviewed: 23 Aug 2023
Last updated: 13 Jun 2023



History and exam

Key diagnostic factors

  • language delay or regression
  • verbal and nonverbal communication impairment
  • social impairment
  • repetitive, rigid, or stereotyped interests, behavior, 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 lamp
  • genetic testing
  • EEG
  • MRI brain
  • audiology
  • specific testing for genetic disorders (e.g., MECP2 deletion)
More investigations to consider

Treatment algorithm


preschool children ages 12 months to 5 years (or equivalent developmental age)

school-age children ages 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 programs 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

Robert Findling, MD, MBA


Department of Psychiatry

Virginia Commonwealth University




RF declares that he has acted as a consultant for, and/or has received honoraria or research support from the following: Acadia, Adamas, Aevi, Afecta, Akili, Alkermes, Allergan, American Academy of Child & Adolescent Psychiatry, American Psychiatric Press, Arbor, Axsome, Daiichi-Sankyo, Emelex, Gedeon Richter, Genentech, Idorsia, Intra-Cellular Therapies, Kempharm, Luminopia, Lundbeck, MedAvante-ProPhase, Merck, MJH Life Sciences, NIH, Neurim, Otsuka, PaxMedica, PCORI, Pfizer, Physicians Postgraduate Press, Q BioMed, Receptor Life Sciences, Roche, Sage, Signant Health, Sunovion, Supernus Pharmaceuticals, Syneos, Syneurx, Takeda, Teva, Tris, and Validus.

Michael Absoud, FRCPCH, PhD

Consultant in Paediatric Neurodisability

Joint Head of Service

Children’s Neurosciences

Reader in Paediatric Neurosciences

Evelina London Children’s Hospital

Department of Women and Children’s Health

King’s College




MA declares that he has no competing interests.

Grant Stewart, BA Hons

Consumer Health and Multimedia Manager

British Medical Journal (BMJ)




GS declares that he is an employee of BMJ.

  • Differentials

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

    • Diagnostic and statistical manual of mental disorders, 5th ed, text revision (DSM-5-TR)
    • 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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