Autism Spectrum Disorder

Autism spectrum disorder is a neurodevelopmental condition of persistent differences in social communication and interaction, with restricted, repetitive patterns of behaviour, interests, or activities.

It is present from early childhood, though not necessarily recognised or diagnosed until later. This applies particularly to individuals with strong compensatory or "masking" strategies, or with milder presentations.

It is a spectrum condition with enormous heterogeneity in presentation, associated cognitive and language ability, and functional impact. At one end are individuals with significant intellectual disability and minimal verbal communication. At the other are individuals with average or above-average cognitive ability and fluent language, who may not be recognised as autistic until adulthood.

Structured, multidisciplinary assessment is essential to accurate diagnosis. Critically, it also identifies the individual's pattern of strengths and needs to inform individualised support.

Pathophysiology and classification

• The pathophysiology reflects a complex interplay of factors. Genetic predisposition is substantial, and heritability is among the highest of the neurodevelopmental conditions. It reflects numerous genetic variants, both common and rare. In a proportion of individuals there is an identifiable genetic syndrome or copy number variant.
• Environmental and prenatal factors contribute in a smaller proportion of cases.
• Neuroimaging and other research show differences in brain structure, connectivity, and function. No single, unifying mechanism has been identified, consistent with the clinical and aetiological heterogeneity of the condition.
• Autism spectrum disorder frequently coexists with other neurodevelopmental and medical conditions:
  • intellectual disability, present in a substantial proportion but by no means the majority of autistic individuals. This proportion has declined over recent decades, reflecting broader diagnostic criteria and better recognition of individuals without intellectual disability
  • attention deficit hyperactivity disorder
  • epilepsy, with substantially increased frequency compared with the general population
  • anxiety disorders
  • gastrointestinal symptoms
• Incidence is increased in certain genetic syndromes, including fragile X syndrome and tuberous sclerosis complex.
• Contemporary understanding increasingly recognises autism as a form of neurodivergence: a different, rather than inherently deficient, pattern of neurological development and cognitive processing.
• Clinical and autistic community perspectives increasingly emphasise identifying and building on individual strengths alongside addressing genuine areas of need and difficulty. This is an important, evolving framework for understanding and supporting autistic individuals.

• Differences in social communication and interaction vary enormously in pattern and severity between individuals. They encompass:
  • difficulty with the reciprocal, back-and-forth nature of typical social conversation and interaction
  • reduced or atypical use and interpretation of non-verbal communication (eye contact, facial expression, and gesture, which may be reduced, absent, or used in an atypical way)
  • difficulty developing, maintaining, and understanding relationships appropriate to developmental level
• Restricted, repetitive patterns of behaviour, interests, or activities encompass:
  • stereotyped or repetitive motor movements, use of objects, or speech
  • insistence on sameness and inflexible adherence to routines
  • highly restricted and intense interests that may be unusual in focus or intensity
  • hyper- or hypo-reactivity to sensory input (apparent indifference to pain or temperature, adverse response to specific sounds or textures, or unusual visual or sensory exploratory interest in objects)
• Sensory differences are increasingly recognised as a common component of the presentation, and for many individuals a significant one.
• Symptoms are present from early developmental periods. They may not become fully manifest, or may not be recognised, until social demands exceed the individual's capacity.
• Learned compensatory strategies may mask them in later childhood, adolescence, or adulthood. This is particularly relevant to the substantial and increasingly recognised population, including many girls and women, who develop significant compensatory or "camouflaging" strategies that can substantially delay recognition and diagnosis.
• Presentation varies considerably with age, cognitive ability, and co-occurring conditions.
• Young children may present with delayed language development, limited or atypical social engagement (including reduced response to their name being called, or limited social smiling and joint attention), and restricted play patterns.
• Older children, adolescents, and adults may present with social and friendship difficulty and significant anxiety, frequently related to social demands or disruption of preferred routines.
• Individuals presenting later in life may describe a longstanding sense of feeling different from peers without a clear, previously identified explanation.

• Diagnosis is by full, structured, multidisciplinary assessment. It generally incorporates:
  • a detailed developmental history, including where possible early childhood development, given the diagnostic requirement for symptom onset within the early developmental period
  • direct, structured behavioural observation using validated, standardised assessment tools designed for this purpose
  • information from multiple relevant sources and settings (parents or carers and, where relevant, school or other settings), to characterise presentation across different contexts
• Assess for coexisting conditions. This includes cognitive and language assessment and screening for attention deficit hyperactivity disorder, anxiety, and other coexisting neurodevelopmental or psychiatric conditions. These conditions frequently coexist and bear directly on individualised support planning.
• No laboratory or neuroimaging test can confirm or exclude the diagnosis. Assessment rests entirely on clinical and behavioural evaluation.
• Consider genetic testing, particularly where additional features (dysmorphism, significant intellectual disability, or a relevant family history) suggest an identifiable underlying genetic syndrome.
• Diagnostic assessment in adults has particular considerations, because substantial compensatory strategies have often developed over years. Assessment generally relies heavily on detailed retrospective developmental history, sometimes supplemented by information from parents or others who know the person's early childhood development. It also includes direct clinical assessment of current presentation and functioning.

• There is no cure for autism spectrum disorder. Contemporary, informed clinical and ethical understanding does not frame autism itself as something requiring "cure" or elimination.
• Management instead focuses on identifying and addressing areas of genuine difficulty or distress, supporting the development of relevant skills, and, critically, adapting the individual's environment to their needs. The aim is not solely to change the autistic individual to conform to neurotypical expectations.
• Early intervention services should be tailored to the needs and profile of the individual child. They include speech and language therapy, occupational therapy (particularly for sensory processing differences and the development of functional and self-care skills), and structured behavioural and developmental intervention approaches. They are particularly valuable when accessed early in a child's development.
• The optimal approach and its evidence base continue to evolve. Emphasis is increasing on approaches that respect and work with, rather than seek to eliminate or suppress, the individual's autistic identity and natural behaviours.
• Manage coexisting conditions, including anxiety, attention deficit hyperactivity disorder, and epilepsy where present, by the standard principles for the underlying condition. Adapt standard treatment carefully to the individual's communication style, sensory sensitivities, and other needs.
• Pharmacological treatment has a limited, generally adjunctive role for the core features of autism itself. It may be considered for specific, significantly impairing associated symptoms.
• For severe irritability or aggression, risperidone and aripiprazole are specifically licensed options in some jurisdictions. For significant sleep disturbance, melatonin is a commonly used, generally well tolerated option.
• Consider pharmacological treatment for these symptoms alongside, not as a substitute for, full behavioural and environmental support strategies.
• Environmental adaptation and accommodation is an essential, often underemphasised component of support. It includes sensory-friendly environmental modifications, clear, predictable routines and communication, and individualised educational support and accommodation. Environmental and contextual factors matter substantially for functioning and wellbeing.
• Provide ongoing psychosocial support for the individual and their family. This includes connection to support services, autism-specific community resources, and, where valued by the individual, peer and community connection with other autistic individuals.
• Provide structured support for transitions: into formal education, between educational stages, and into adulthood and, where relevant, employment.
• This underpins individualised, respectful long-term support across the lifespan for this common, lifelong neurodevelopmental condition. The overarching goal is to enable each individual to thrive according to their own strengths, needs, and goals, rather than to enforce conformity to an externally defined standard of typical functioning. Mext 3