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Asperger's syndrome

Autistic spectrum disorder

Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Autistic spectrum disorders article more useful, or one of our other health articles.

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What is autistic spectrum disorder?

Autistic spectrum disorder (ASD) is a pervasive developmental disorder. First described by Hans Asperger in 1944, ASD lies within the autistic spectrum. Previously it was called high-functioning autism or Asperger's syndrome. The main difference from classic autism is a lack of delayed or retarded cognition and language. Those with ASD are also more likely to seek social interaction and share activities and friendships.

The major classification systems (see below) refer to autistic spectrum disorder (ASD) and do not include specific reference to Asperger's syndrome. However many people, particularly some people with autistic spectrum disorder and their families, still prefer to use the term Asperger's syndrome. See also the article on Autistic Spectrum Disorders for further information.

Classification1 2

There are two major diagnostic classification systems in current use, the International Classification of Diseases version 11 (ICD-11) and the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5).

Because the disorder spectrum concept (autistic spectrum disorder, or ASD) has now been fully integrated into autism classification, the condition of AS (or Asperger's syndrome) is no longer used.

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How common is autistic spectrum disorder? (Epidemiology)3

  • Autism spectrum disorder (ASD) is one of the most common childhood onset neurodevelopmental disorders. The estimated prevalence in children is at least 1%.

  • There are about 3-4 times more boys affected by ASD than girls, although this varies across the spectrum. Girls are more likely to have a learning (intellectual) disability.

  • However, there is evidence that ASD may be under-recognised in girls without a learning (intellectual) disability.

What causes autistic spectrum disorder? (Aetiology)4

ASD is not a single disorder. It is now broadly considered to be a multi-factorial disorder resulting from genetic and non-genetic risk factors and their interaction.

  • Genetic causes including gene defects and chromosomal anomalies have been found in 10-20% of individuals with ASD. Siblings born in families with an ASD subject have a 50 times greater risk of ASD, with a recurrence rate of 5-8%. The concordance rate reaches up to 82-92% in monozygotic twins, compared with 1-10% in dizygotic twins.

  • Genome-wide linkage studies suggested linkages on chromosomes 2q, 7q, 15q and 16p as the location of susceptibility genes.

  • Metabolic errors including phenylketonuria, creatine deficiency syndromes, adenylosuccinate lyase deficiency and metabolic purine disorders account for fewer than 5% of individuals with ASD.

  • A correlation between cerebellar developmental patterning gene ENGRAILED 2 and autism has been reported. It is the first genetic allele that contributes to ASD susceptibility in as many as 40% of ASD cases.

  • Other genes such as UBE3A locus, GABA system genes and serotonin transporter genes have also been considered as the genetic factors for ASD.

  • Various environmental factors may also contribute to ASD, including:

    • Prenatal factors such as advanced parental age, exposure to teratogens (eg, thalidomide, maternal anticonvulsants such as valproic acid and organophosphates), maternal diabetes and certain viral infections (eg, congenital rubella syndrome, influenza, cytomegalovirus).

    • Perinatal factors such as low birth weight, abnormally short gestation length and birth asphyxia.

    • Postnatal factors such as autoimmune disease, viral infection, hypoxia and mercury toxicity.

Current evidence indicates that there is no harmful association between MMR vaccine and ASD even among children already at higher risk of ASD (ie children with older siblings with ASD).5

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Autistic spectrum disorder symptoms (presentation)3

The severity and impact of ASD varies greatly depending on age, development, and presence or absence of associated conditions.

Autistic spectrum disorder is associated with a higher functional ability than autism. People with autistic spectrum disorder usually have fewer problems with speech and are often of average or above average intelligence.

People with AS do not usually have the learning disabilities associated with autism but they may have specific learning difficulties.

AS usually causes fewer problems with speech but there may still be difficulties with understanding and processing language.

In classic autism, children tend to be spotted earlier (18-30 months) because of impaired communication. In AS, the diagnosis comes later - usually at school entry, when socialisation becomes necessary. Many people with AS may learn to mask their problems. They may present as patients with no serious mental health problem but who are anxious, are lonely, have a poor employment record and just don't seem to fit in.


There is normal speech development before the age of 4 years, with good grammar and vocabulary. However, their tone is flat and they are pedantic. They also have a restricted repertoire of subjects. They have poor non-verbal communication skills.

They may take language very literally and be unable to interpret idiom. For example, if you use the phrase 'in a nutshell', they will be confused about how what you are saying is going to end up inside a nut.


They are often obsessed with complex subjects and described as 'eccentric' or 'little professors'. IQ is normal - above average. They score well in verbal ability but below average in performance abilities. Patients with AS may be highly creative and have exhibited outstanding skills in mathematics, music and computer sciences. Their strength lies in concrete, rather than abstract, thinking.

They have poor powers of imagination. They lack an intuitive theory of mind (ability to imagine what others are thinking or feeling) and are often unable to talk about their own emotions, which may lead to anxiety and depression in later life.

They also lack central coherence. This is the ability to integrate individual elements of perception into an overall context of meaning, ie seeing the 'bigger picture'. The following statement could be typical of a patient with AS: "I see hundreds of individual trees but I cannot see a forest." They tend to be detail-orientated and have great difficulty understanding the overall context.


There are delayed motor milestones and then clumsiness. There are poor sleep patterns. They experience difficulties falling, and staying, asleep. They are more interested in others compared with people with more severe forms of autism, but do not share interests. Their interaction is one-sided. They are solitary, with no friends, and socially aware - but may display inappropriate reciprocal interaction. They may be seen as eccentric.

Associated medical problems

Associated medical conditions are much less common for people with AS than for people with more severe forms of ASD.

  • Epilepsy: 25-30% of children on the autistic spectrum may have seizures. This usually appears in puberty.6 These are more common in children who have significant cognitive problems or dysmorphic features.

  • Visual impairment; hearing impairment.

  • Mental health:7

    • Depression, anxiety and obsessive-compulsive disorder are reported to be particularly common in younger adults with ASD.

    • Studies suggest that 30-84% of adults with ASD might have some form of diagnosable mental illness.8

    • Neurodevelopmental disorders such as attention deficit hyperactivity disorder (ADHD) are common in adults with ASD.

    • The prevalence of mental health disorders is increased in those with both severe general learning disability and ASD.

  • General learning disability.

  • Underlying medical conditions, such as untreated phenylketonuria, congenital rubella, cytomegalovirus or toxoplasmosis, fragile X syndrome or tuberous sclerosis.

  • Sleep disorders are common.

Screening tools8

  • Population screening for ASD is not recommended in the UK. False positive or false negative results from inappropriate use of screening tests may delay the correct diagnosis. The decision about the need for referral and further assessment should be made on clinical grounds.

  • However, ASD-specific assessment tools may be used to supplement the process of clinical history taking - eg, the Autism Diagnostic Interview, Revised (ADI-R), the Diagnostic Interview for Social and Communication Disorders (DISCO) and the Developmental, Dimensional and Diagnostic Interview.

  • The Autism Spectrum Quotient-10 instrument may be used to help identify adults with possible ASD who should be referred for further assessment.

  • A negative result from an assessment does not necessarily rule out the diagnosis. If parental concerns continue, a referral is advisable.9

  • The assessment of children and young people with developmental delay, emotional and behavioural problems, psychiatric disorders, impaired mental health or genetic syndromes should include surveillance for ASD as part of routine practice.

Differential diagnosis

Making the diagnosis10

The condition can be reliably diagnosed between 2-3 years of age. The National Institute for Health and Care Excellence (NICE) has published guidance for assessment and referral of children with suspected ASD:

  • Specialist diagnosis is required. This is probably best done by paediatric neurologists, developmental and behavioural paediatricians, child psychiatrists or psychologists. Ideally there should be a multidisciplinary team ('the ASD team'), with specific training and experience in evaluating children with ASD.

  • Involvement of speech and language and occupational therapists, special educators, and social workers may provide a more detailed assessment of specific domains.

  • Other conditions need to be excluded and investigations for chromosome analysis and hearing and sight tests, are usually taken prior to reaching the diagnosis. Where clinically relevant, the following should be considered for all children and young people with ASD:

    • Examination of physical status, with particular attention to neurological and dysmorphic features.

    • Karyotyping and fragile X DNA analysis.

    • Hearing examination.

    • Investigations to rule out recognised causes of ASD - eg, tuberous sclerosis.

  • Assessments of children and young people for ASD cannot be rushed. It may not be possible to obtain sufficient evidence in one session and the child/young person may require observation in different settings - eg, at school (especially in unstructured activity such as break-time) as well as at the clinic.

  • ASD is diagnosed when an individual exhibits six or more symptoms across the three core areas.

  • All children and young people with ASD should have a comprehensive assessment of their speech, language and communication skills. This will help to decide which interventions are best suited for that child.

Referring children and young people to the 'ASD team'10

Early assessment, diagnosis and intervention are very important. Indications for specialist referral for further assessment include:

  • Refer children younger than 3 years to the 'ASD team' if there is regression in language or social skills.

  • Refer first to a paediatrician or paediatric neurologist (who can refer to the 'ASD team' if necessary) children and young people who are older than 3 years with regression in language, or of any age with regression in motor skills.

  • Consider referring children and young people to the 'ASD team' if you are concerned about possible ASD on the basis of reported or observed signs and/or symptoms. Take account of:

    • The severity and duration of the signs and/or symptoms.

    • The extent to which the signs and/or symptoms are present across different settings (eg, home and school).

    • The impact of the signs and/or symptoms on the child or young person and on their family.

    • The level of parental or carer concern and, if appropriate, the concerns of the child or young person.

  • Factors associated with an increased prevalence of ASD.

  • The likelihood of an alternative diagnosis.

Autistic spectrum disorder treatment8

Prompt diagnosis and appropriate intervention, specialised educational programmes and structured support may help a person with ASD to maximise his/her potential.

Management is usually undertaken in educational settings. Local support networks may be in place for educational support in mainstream school if appropriate and will feed down from paediatrician or educational psychologist. Occupational therapy, speech therapy and physiotherapy may help specific problems.

Non-pharmacological interventions

Children and young people

  • Parent-mediated interventional programmes should be considered, as they may help families interact with their child, promote development and increase parental satisfaction, empowerment and mental health.

  • Behavioural and other psychological interventions:

    • Behavioural and other psychological interventions include intensive behavioural and developmental programmes aimed at improving overall functioning and altering outcome, and interventions which aim to address specific behavioural difficulties associated with ASD, such as sleep disturbance, or to increase positive behaviours such as initiating social contact with peers.

    • Behavioural therapies may be considered to address a wide range of specific behaviours, including challenging behaviours, both to reduce symptom frequency and severity and to increase the development of adaptive skills. Behavioural therapy should also be considered for children who experience sleep problems.

    • Early intensive behavioural intervention (EIBI) programmes:

      • EIBI programmes aim to engage the child with ASD in a structured learning programme that is highly individualised, taking into account the idiosyncratic motivations and specific needs of each child.

      • EIBI programmes attempt to address a comprehensive range of behaviours associated with ASD, rather than focusing on one specific aspect such as communication, social skills or interaction.

      • Programmes vary considerably in terms of technologies and emphasis but are all based on applied behaviour analysis (ABA).

      • ABA-based and intensive programmes increasingly include developmental programmes such as the Learning Experiences and Alternative Program for Preschoolers and their parents (LEAP) and the Early Start Denver Model (ESDM).

      • EIBI programmes are intensive and target a comprehensive range of skills for training, practice and generalisation.

    • Cognitive behavioural therapy (CBT) may be considered, using a group format where available and appropriate, to treat anxiety. The delivery of CBT should be adapted for people with ASD.

  • Communication interventions:

    • Many children and young people with ASD have little or no speech. Those who do have speech have difficulties in using language effectively (pragmatic language impairment or social communication difficulty).

    • Many of the strategies implemented to support communication are designed and managed by speech and language therapists, working in partnership with parents.

    • Speech and language therapy is most effective when speech and language therapists also train and work with teachers, families and peers promoting functional communication in normal environments. Interventions to support communicative understanding and expression, such as the Picture Exchange Communication System and the use of environmental visual supports (eg, in the form of pictures or objects), should be considered.

    • Interventions to support social communication should be considered. Social skills (attention, interactive play, responding to social overtures and initiating and maintaining social behaviours) can be taught explicitly.

    • When children are school-aged, social skills groups can be useful. Using videos and social stories can help to teach specific skills.

  • Occupational therapy:

    • Sensory integration therapy has been used when there are marked sensory perception issues - eg, over-sensitivity to touch. Occupational therapists desensitise the child gently over time.

    • Occupational therapy also focuses on development and maintenance of fine motor and adaptive skills.

    • Children and young people affected by ASD may benefit from occupational therapy, advice and support in adapting environments, activities and routines in daily life.

  • Other interventions:

    • Music therapy may help improve skills in social interaction, verbal communication, initiating behaviour and social-emotional reciprocity in the short to medium term.

    • Systematic reviews of complementary therapies, acupuncture and animal-assisted interventions reported that evidence for the use of complementary and alternative therapies for individuals with ASD is sparse and no strong conclusions could be drawn.

    • Advice on diet and food intake should be sought from a dietician for children and young people with ASD who display significant food selectivity and dysfunctional feeding behaviour, or who are on restricted diets that may be adversely impacting on growth, or producing physical symptoms of recognised nutritional deficiencies or intolerances.


  • Psychosocial interventions can be used to target a range of outcomes in adults with ASD, including adaptive behaviours, communication, social skills, employment, quality of life and comorbid mental health difficulties.

  • Social programmes involve communication and behavioural elements. Most psychosocial interventions aimed at improving outcomes for adults have been developed for children and young people and there is less evidence about their efficacy in adulthood.

  • Psychosocial interventions should be considered for adults with ASD if indicated for managing co-existing conditions. There is insufficient evidence to recommend any specific model of psychosocial intervention. However, a diagnosis of ASD should not prevent anyone from receiving these interventions.

  • Therefore, if an individual with ASD experiences a symptom or condition (eg, anxiety) that would usually be treated with CBT or related psychosocial intervention, they should receive the intervention recommended by guidelines for that symptom or condition.

  • Interventions to improve emotional literacy, distress tolerance, relaxation skills or general adjustment may considered as first-line interventions.

Pharmacological management

The management of ASD is essentially non-pharmacological. However, certain drugs may be considered for the management of co-existing psychiatric or neurodevelopmental conditions and may occasionally have a short-term adjunctive role in alleviating core symptoms of ASD. Any pharmacological intervention should only be undertaken by doctors with appropriate training in the care of people with ASD.


  • Autism spectrum disorder (ASD) is a lifelong disorder and has a great impact on the child or young person and their family and/or carers. However, ASD varies greatly in terms of the level of impairments, which influence the prognosis.

  • The presence or absence of associated learning (intellectual) disability, language impairment, and additional mental health problems are the most important prognostic factors. Unaffected language development and the absence of an associated intellectual disability are associated with a more favourable prognosis.

  • The prognosis of ASD can be improved by early diagnosis and assessment because this aids understanding of why the child or young person is different from their peers.

  • The lives of people with ASD and their family and/or carers can be greatly improved by early diagnosis and prompt access to:

    • Support and services in education, health services, and social care.

    • A route into voluntary organisations.

    • Contact with other children and families with similar experiences.

Further reading and references

  • National Autistic Society
  • Roy M, Dillo W, Emrich HM, et al; Asperger's syndrome in adulthood. Dtsch Arztebl Int. 2009 Jan;106(5):59-64. doi: 10.3238/arztebl.2009.0059. Epub 2009 Jan 30.
  • Sanchack KE, Thomas CA; Autism Spectrum Disorder: Primary Care Principles. Am Fam Physician. 2016 Dec 15;94(12):972-979.
  1. International Classification of Diseases 11th Revision; World Health Organization, 2019/2021
  2. Highlights of Changes from DSM-IV-TR to DSM-5; American Psychiatric Association, 2013
  3. Autism in children; NICE CKS, August 2020 (UK access only)
  4. Park HR, Lee JM, Moon HE, et al; A Short Review on the Current Understanding of Autism Spectrum Disorders. Exp Neurobiol. 2016 Feb;25(1):1-13. doi: 10.5607/en.2016.25.1.1. Epub 2016 Jan 28.
  5. Jain A, Marshall J, Buikema A, et al; Autism occurrence by MMR vaccine status among US children with older siblings with and without autism. JAMA. 2015 Apr 21;313(15):1534-40. doi: 10.1001/jama.2015.3077.
  6. Pickett J, Xiu E, Tuchman R, et al; Mortality in Individuals With Autism, With and Without Epilepsy. J Child Neurol. 2011 Apr 6.
  7. Foley KR, Trollor J; Management of mental ill health in people with autism spectrum disorder. Aust Fam Physician. 2015;44(11):784-90.
  8. SIGN 145 Assessment diagnosis and interventions for autism spectrum disorders; Scottish Intercollegiate Guidelines Network - SIGN (2016, revalidated August 2019)
  9. Blenner S, Reddy A, Augustyn M; Diagnosis and management of autism in childhood. BMJ. 2011 Oct 21;343:d6238. doi: 10.1136/bmj.d6238.
  10. Autism in under 19s: recognition, referral and diagnosis; NICE Clinical Guideline (September 2011 - last updated December 2017)

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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