Autistic Spectrum Disorders

Authored by , Reviewed by Dr Hayley Willacy | Last edited | Certified by The Information Standard

This article is for Medical Professionals

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Synonym: autism, autistic spectrum condition (ASC)

Autistic spectrum disorder (ASD) is a complex developmental condition that includes a range of possible developmental impairments in reciprocal social interaction and communication, and also a stereotyped, repetitive or limited behavioural repertoire. Sensory differences may also be a presenting feature. ASD may occur in association with any level of general intellectual or learning ability and the presentation ranges from subtle problems of understanding and impaired social function to severe disabilities. Impairments in each of the areas relevant to ASD occur along a continuum from minimal to severe.[1]

There are two major diagnostic classification systems in current use, the International Classification of Diseases version 10 (ICD-10) and the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5). DSM-5 is the most recently updated classification system, published in 2013. ICD-10 was published in 1993 and ICD-11 is due for publication in 2017. Either of the current versions of ICD or DSM can be used for diagnosis but the classification system used for diagnosis should be clearly recorded.

ICD-10 defines autism as a type of pervasive developmental disorder (PDD), a group of disorders characterised by qualitative abnormalities in reciprocal social interactions and in patterns of communication, and by a restricted, stereotyped, repetitive repertoire of interests and activities. These qualitative abnormalities are a pervasive feature of the individual's functioning in all situations.

Autism is defined by:

  • The presence of abnormal or impaired development that is manifest before the age of 3 years; and
  • The characteristic type of abnormal functioning in all the three areas of psychopathology: reciprocal social interaction, communication and restricted, stereotyped, repetitive behaviour.

In addition to these specific diagnostic features, a range of other nonspecific problems is common, such as phobias, sleeping and eating disturbances, temper tantrums and (self-directed) aggression.[2]

The most important difference between ICD-10 and DSM-5 is that DSM-5 uses the concept of autistic spectrum disorder (ASD) rather than the concept of pervasive developmental disorders (PDDs). Whilst the conditions of childhood autism and Asperger's syndrome are included in PDD, the concept of an autism spectrum is not.

Another significant difference between DSM-5 and ICD-10 is that, because the disorder spectrum concept has now been fully integrated into autism classification, the condition of Asperger's syndrome (or Asperger's disorder from DSM-IV) is no longer used. The DSM-5 classification also adds in new clinical signs of stereotypical speech and also hyperreactivity or hyporeactivity to sensory input or interest in sensory aspects of the environment.

The new DSM-5 dimension of "persistent deficits in social communication and social interaction across multiple contexts" reflects the view that problems with reciprocal social interaction and communication overlap and cannot be reliably distinguished. The second diagnostic dimension of the DSM-5 is of restricted, repetitive patterns of behaviour, interests, or activities.

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).[4]

  • A community survey in England in 2007 estimated that about 1% of adults have ASD. The prevalence in children is also around 1%.
  • A study in greater Glasgow of children aged 0-6 years reported a prevalence of autism of 11.1 per year per 10,000 children in 2007.
  • ASD is more commonly diagnosed in boys than in girls, with a ratio of approximately 4:1, although this varies across the spectrum of ASD.

ASD can be recognised for the first time at any age, despite the fact that it is a lifelong disorder that starts in early life. Some people will not present until later in life. The possibility of an ASD diagnosis may present in education, social work and employment settings. People may present at any time but particularly at times of change or stress - eg, when moving to university, after the death of a spouse or at times of work or life stress

However, it is reported that at least 50% of parents have cause for concern by the child reaching 12-18 months of age.[5]

Indicators of possible ASD include:

Preschool children

  • Delay or absence of spoken language.
  • The child looks through people and is not aware of others. He/she is not responsive to other people's facial expression or feelings
  • Lack of pretend play; little or no imagination; does not show typical interest in or play purposefully near others; lack of turn-taking; unable to share pleasure; lack of initiation of activity or social play.
  • Impairment in non-verbal communication; does not point at an object to direct another person to look at it; lack of gaze monitoring.
  • Unusual or repetitive hand and finger mannerisms.
  • Unusual reactions, or lack of reaction, to sensory stimuli.

Children of school age

  • Communication impairments: abnormalities in language development including:
    • Muteness, odd or inappropriate rhythm and pattern of language, persistent echolalia.
    • Reference to self as 'you', 'she' or 'he' beyond 3 years.
    • Unusual vocabulary for the child's age/social group; limited use of language for communication and/or a tendency to talk freely only about specific topics.
    • Impairment in non-verbal communication.
  • Social impairments:
    • Inability to join in play of other children or inappropriate attempts at joint play (apparent aggressive or disruptive behaviour).
    • Lack of awareness of classroom 'norms' (criticising teachers, overt unwillingness to co-operate in classroom activities, inability to appreciate or follow current trends).
    • Easily overwhelmed by social and other stimulation, failure to relate normally to adults (too intense/no relationship).
    • Showing extreme reactions to invasion of personal space and resistance to being hurried.
  • Impairments of interests, activities and/or behaviours:
    • Lack of flexible co-operative imaginative play/creativity.
    • Difficulty in organising self in relation to unstructured space (eg hugging the perimeter of playgrounds, halls).
    • Inability to cope with change or unstructured situations, even ones that other children enjoy (school trips, teachers being away etc).
  • Other behaviour:
    • Any other evidence of odd behaviours, including unusual responses to sensory stimuli.


The following indicators are in addition to those in younger children. Difficulties are likely to be more subtle in older individuals or those without intellectual disability:

  • Long-standing difficulties in social behaviours, communication and coping with change, which are more obvious at times of transition (eg, change of school, leaving school).
  • Significant discrepancy between academic ability and 'social' intelligence, most difficulties in unstructured social situations - eg, in school or work breaks.
  • Socially 'naïve'; lacking common sense; not as independent as peers.
  • Language, non-verbal skills and social communication:
    • Problems with communication, even if there is wide vocabulary and normal use of grammar.
    • May be unduly quiet; may talk at others rather than hold a proper conversation.
    • May provide excessive information on topics of own interest; unable to adapt style of communication to social situations - eg, may sound overly formal or be inappropriately familiar.
    • May have speech peculiarities, including 'flat' unmodulated speech, repetitiveness and use of stereotyped phrases.
    • May take things literally and fail to understand sarcasm or metaphor; unusual use and timing of non-verbal interaction (eg, eye contact, gesture and facial expression).
  • Social problems:
    • Difficulty making and maintaining peer friendships, although the child may find it easier with adults or younger children; can appear unaware or uninterested in peer group 'norms'.
    • May alienate by behaviours which transgress 'unwritten rules'.
    • May lack awareness of personal space, or be intolerant of intrusions on own space.
  • Rigidity in thinking and behaviour:
    • Preference for highly specific, narrow interests or hobbies, or may enjoy collecting, numbering or listing; strong preferences for familiar routines.
    • May have repetitive behaviours or intrusive rituals; problems using imagination - eg in writing and in future planning.
    • May have unusual reactions to sensory stimuli - eg, sounds, tastes, smell, touch, heat or cold.


  • Persistent difficulty in social interaction.
  • Persistent difficulty in social communication.
  • Stereotypical (rigid/repetitive) behaviours; resistance to change.
  • Restricted interests.
  • Problems with obtaining/sustaining employment/education.
  • Difficulty in initiating or sustaining social relationships.

Adults who have a moderate or severe intellectual disability

  • Presence of two or more of the following:
    • Difficulties in reciprocal social interaction, including: limited interaction with others (eg, being aloof, indifferent or unusual); interaction to fulfil needs only; interaction that is naïve or one-sided.
    • Lack of responsiveness to others.
    • Little or no change in behaviour in response to different social situations.
    • Limited social demonstration of empathy.
    • Rigid routines and resistance to change.
    • Marked repetitive activities (eg, rocking and hand or finger flapping), especially when under stress or expressing emotion.

Children and adults with severe intellectual disability without ASD

These individuals may present with rigid routines, repetitive activities and limited empathy.

Children and adults with severe intellectual disability with ASD

These individuals will present with a more significant level of such difficulties with a qualitative autistic difference.

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.[5]

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.

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.
  • Autistic disorder 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'[8]

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.

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:
      • Early intensive behavioural intervention (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.

  • ASD is a lifelong disorder and has a great impact on the child or young person and their family or carers.
  • ASD varies greatly in terms of level of impairments which influence the prognosis. A minority of affected people with lower level impairment live and work independently in adulthood.
  • However, there is evidence that adult outcomes are poor and adult developmental milestones such as work, intimate relationships or independence from parents are often not achieved.[1]
  • The presence or absence of associated 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, with the provision of support and services in education, health services, social care, and voluntary organisations, and contact with other families with similar experiences.

The term autism was first used by psychiatrist Eugen Bleuler in 1911, to describe a person with schizophrenia who had withdrawn into his own world. Hans Asperger and Leo Kanner both used the term in the 1940s, working separately. Asperger described very able children. Kanner described children who were severely affected. His description, and the downbeat prognosis, persisted for the next 30 years.

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Further reading and references

  1. SIGN 145 Assessment diagnosis and interventions for autism spectrum disorders; Scottish Intercollegiate Guidelines Network - SIGN (2016)

  2. The ICD-10 Classification of Mental and Behavioural Disorders; World Health Organization

  3. Park HR, Lee JM, Moon HE, et al; A Short Review on the Current Understanding of Autism Spectrum Disorders. Exp Neurobiol. 2016 Feb25(1):1-13. doi: 10.5607/en.2016.25.1.1. Epub 2016 Jan 28.

  4. 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 21313(15):1534-40. doi: 10.1001/jama.2015.3077.

  5. Blenner S, Reddy A, Augustyn M; Diagnosis and management of autism in childhood. BMJ. 2011 Oct 21343:d6238. doi: 10.1136/bmj.d6238.

  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. 201544(11):784-90.

  8. Autism in under 19s: recognition, referral and diagnosis; NICE Clinical Guideline (September 2011)

  9. Autism; NICE CKS, June 2014 (UK access only)

Hi everyone, I have s little boy that is a few days shy from 20 months old. He says 4 words 2 of which are strong and clear (mama, dada) and two which he doesn't use often and only seems to whisper (...

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