Autism Spectrum Disorder (ASD)
General Psychiatry Article Disclaimer
- DSM-5 criteria or ICD-11 diagnostic requirements are used to structure the Clinical Features and Diagnosis section. The classification system used is selected according to its clarity and suitability for non-specialist learning.
- The criteria are summarised and simplified rather than reproduced in full, while preserving their original diagnostic meaning.
- Where appropriate, a student-friendly pattern-recognition summary is provided to highlight the most clinically and exam-relevant features.
Exam tip (re-psychiatry questions)
- Do not attempt to memorise every DSM-5 or ICD-11 criterion word-for-word. However, it is important to read through the criteria and become familiar with the key symptom clusters, duration thresholds, exclusions, and distinguishing features highlighted in this article.
- Exam questions may not provide every feature required to meet the full diagnostic criteria. Familiarity with the criteria can help one recognise the most likely diagnosis, exclude important alternatives, and narrow the differential diagnosis.
Terminology: Autism and Asperger Syndrome
Autism spectrum disorder (ASD) is the formal diagnostic term, while autism is commonly used as a shorter umbrella term. The word “spectrum” is used to capture the wide variation between individuals with autism.
The term “Asperger syndrome” was historically used to describe autistic people without intellectual disability or significant early language delay.
In the most recent diagnostic systems (both DSM-5 and ICD-11), the specific diagnosis of “Asperger’s disorder” was removed and integrated under the single umbrella term of ASD.
Causes and Risk Factors
Autism spectrum disorder is a highly heritable and heterogeneous neurodevelopmental disorder driven by a complex interaction of genetic factors and environmental factors. [Ref]
| Genetic factors | >100 genes and genomic regions have been identified to be associated with autism
Genes associated with syndromic autism (where autism is part of a broader genetic condition):
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| Environmental factors | Established environmental factors that are associated with autism:
Folic acid intake has been identified as a protective factor against autism There is clear, definitive evidence that autism is not associated with vaccination |
Associated Conditions / Comorbidities
| System / category | Associated conditions / comorbidities |
|---|---|
| Psychiatric and behavioural |
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| Neurological and developmental |
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| Systemic |
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| Genetic syndromes | Syndromic autism (monogenic syndromes where autism is often part of the syndrome’s wider manifestation):
Other notable genetic associations:
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Recognition and Referral
In Children and Young People (<19 y/o)
NICE noted that concerns about development or behaviour from parents, carers, or the child should always be taken seriously.
Referral:
- Immediate referral to autism team for comprehensive assessment if a <3 y/o child with regression in language or social skills
- Referral to paediatric / neurology if
- >3 y/o child with language regression, or
- Child of any age with motor skill regression
Do not rule out autism just because a child has good eye contact, shows affection, hits normal language milestones, or engages in pretend play
In Adults
Consider assessing an adult for autism if a patient presents with:
- Persistent difficulties in social interaction or communication, and
- Stereotypic (rigid and repetitive) behaviours, resistance to change, or restricted interests, and
- At least one functional impact (e.g. problems obtaining or sustaining employment/education, difficulties with social relationships, or a history of contact with mental health or learning disability services)
If the adult is suspected to have autism → refer to specialist for comprehensive assessment
- If the adult does NOT have a moderate or severe learning disability, NICE recommends using the AQ-10
Clinical Features and Diagnosis
High-yield pattern recognition for autism:
Core symptoms:
- Impairments in social communication and interaction
- Reduced social-emotional reciprocity
- Impaired non-verbal communication
- Difficulty in understanding, developing, and maintaining relationships
- Restricted and repetitive behaviours
- Highly restricted or fixated interests
- Sensory anomalies (such as hypersensitivity or hyposensitivity to sensory inputs)
Autism is a clinical diagnosis through a comprehensive specialist assessment. DSM-5 criteria: [Ref]
| Diagnostic criteria | Criteria description |
|---|---|
| Impaired social communication and interaction | There must be persistent difficulties in social communication and social interaction across different contexts, demonstrated currently or historically in all 3 of the following areas:
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| Restricted or repetitive behaviours | There must be restricted or repetitive patterns of behaviour, interests or activities, demonstrated currently or historically by at least 2 of the following 4 areas:
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| Developmental onset |
The above features must have been present during the early developmental period However, they may:
Therefore, it is possible for autism to only be diagnosed in adulthood |
| Functional impact | The above features must cause clinically significant difficulty in social, occupational, educational or other important areas of current functioning |
| Exclusion and intellectual disability | The presentation must NOT be better explained solely by:
|
Do NOT routinely use biological tests, genetic tests, or neuroimaging to help diagnose autism.
Management
Psychosocial interventions are the mainstay of management for the core features of autism
Psychosocial interventions vary by age group and should be tailored to the individual’s needs: [Ref]
| Age group | Intervention approach |
|---|---|
| Pre-school |
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| School-aged children and adolescents |
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| Adulthood |
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Management of challenging behaviours:
- First identify and address any underlying triggers (e.g. physical pain, environmental factors, co-existing mental disorders)
- If there are no triggers → psychosocial intervention
- Antipsychotics can be considered if the challenging behaviour does not respond to other interventions, or if the behaviour prevents the delivery of psychosocial interventions
Medications should NOT be used to treat the core symptoms of autism; they are strictly used to treat associated symptoms and comorbidities. Examples include:
- Stimulants (e.g. methylphenidate) for ADHD
- SSRIs for anxiety, depression and OCD
NICE explicitly recommended against the use of the following to manage core autism features:
- Exclusion diets (e.g. gluten-free, casein-free, ketogenic diets)
- Vitamins, minerals, dietary supplements
- Chelation, hyperbaric oxygen therapy, testosterone regulation, oxytocin, secretin
- Cholinesterase inhibitors (e.g. donepezil)