Autism Spectrum Disorder

Introduction

Autism spectrum disorder is a lifelong neurodevelopmental condition characterised by persistent differences in social communication and social interaction, together with restricted, repetitive patterns of behaviour, interests or activities, including sensory differences.¹ Features are present from early development, although they may only become fully apparent when social demands exceed the person's capacity to compensate.

Prevalence in the UK is estimated at around 1-2%, and recorded diagnoses have risen substantially over recent decades. This reflects broadened diagnostic criteria, better recognition - particularly of people without intellectual disability and of women and girls - and greater awareness, rather than a true epidemic. The historical separation of 'Asperger syndrome' from autism has been removed in both ICD-11 and DSM-5, replaced by a single spectrum diagnosis with specifiers for language and intellectual ability.

The framing of autism has shifted considerably. It is increasingly understood as a difference in neurological development rather than purely a disorder to be corrected, and many autistic people identify with this neurodiversity perspective and prefer identity-first language ('autistic person'). This is not merely terminology: it shapes management, where the goal is to adapt the environment and support the individual rather than to make them appear less autistic. That said, autism is also genuinely disabling for many, and support needs range from minimal to requiring lifelong 24-hour care.

Aetiology

Autism is strongly genetic and neurodevelopmental in origin, with brain differences established prenatally and in early infancy.

• Genetics - heritability is high, estimated at 70-90%. It is largely polygenic, with hundreds of contributing common variants, plus rare de novo mutations and copy number variants in a minority.
• Syndromic associations - fragile X syndrome (the commonest single inherited cause), tuberous sclerosis, Rett syndrome, Down syndrome, neurofibromatosis and untreated phenylketonuria
• Neurodevelopmental differences - atypical early brain overgrowth, altered synaptic pruning, and differences in connectivity between brain regions, particularly affecting networks involved in social cognition
• Prenatal factors - advanced parental age, prenatal sodium valproate exposure (a well-established and important association), maternal infection during pregnancy, extreme prematurity and low birth weight
• Not caused by vaccines. The MMR hypothesis originated in a small, fraudulent 1998 paper that was fully retracted, and its author was struck off. Multiple very large studies across several countries have found no association. Confidently and clearly rebutting this claim is a genuine clinical skill.
• Not caused by parenting. The 'refrigerator mother' theory was discredited decades ago but has left a lasting legacy of parental guilt worth addressing directly.

Clinical features

Social communication and interaction

• Social-emotional reciprocity - difficulty with the back-and-forth of conversation, reduced sharing of interests or emotions, difficulty initiating or responding to social approaches
• Non-verbal communication - differences in eye contact, facial expression, gesture and body language, and difficulty interpreting these in others
• Relationships - difficulty developing, maintaining and understanding friendships, adjusting behaviour to different social contexts, or sharing imaginative play
• Language - ranges from complete absence of speech to fluent but literal or formal language. Difficulty with sarcasm, idiom, implication and irony is common; a preference for direct, explicit communication is not rudeness.
• Theory of mind differences - difficulty inferring others' intentions, beliefs and perspectives, and correspondingly, neurotypical people find it equally difficult to read autistic communication - the mismatch runs in both directions

Restricted and repetitive behaviours

• Stereotyped or repetitive movements ('stimming') - hand flapping, rocking, spinning, finger flicking. These are usually self-regulatory and calming, and suppressing them is generally unhelpful and distressing.
• Insistence on sameness - distress at small changes, rigid adherence to routines, ritualised patterns of behaviour, difficulty with transitions
• Highly restricted, fixated interests - abnormal in intensity or focus, often a source of genuine expertise and pleasure and a strength to be built on rather than discouraged
• Sensory differences - hyper- or hypo-reactivity to sound, light, touch, texture, taste or smell; fascination with lights or spinning objects; apparent indifference to pain or temperature. Sensory overload is frequently the most disabling day-to-day feature and a common trigger for distress.
• Echolalia - repeating words or phrases, immediately or delayed

Associated presentations

• Meltdowns - an involuntary response to overwhelming sensory or emotional load, distinct from a tantrum in that it is not goal-directed and cannot be stopped by negotiation. Shutdowns are the withdrawn equivalent.
• Masking or camouflaging - consciously suppressing autistic traits, rehearsing conversations, forcing eye contact and imitating social behaviour. It is exhausting, delays diagnosis, and is strongly associated with anxiety, depression, burnout and suicidality.
• Uneven skill profile - marked strengths in some areas alongside significant difficulty in others, which frequently leads to underestimation of support needs

Comorbidity and differential diagnosis

Differential diagnosis

• Social (pragmatic) communication disorder - communication difficulties without the restricted, repetitive behaviours
• Intellectual disability - global developmental delay without the specific social communication profile, though the two frequently coexist
• Hearing impairment - a critical exclusion in any young child with delayed language or apparent unresponsiveness; always check the newborn hearing screen result and arrange audiology
• Selective mutism - speech is absent in specific settings but normal elsewhere
• Social anxiety disorder - social avoidance driven by fear of negative evaluation, with social skills intact when comfortable
• ADHD - inattention may look like social disengagement; frequently comorbid rather than alternative
• Attachment disorder and early deprivation - can produce social difficulties that mimic autism and requires careful, expert differentiation
• Schizophrenia - negative symptoms and social withdrawal, but with onset after a period of typical development and with positive psychotic symptoms

Assessment and investigations

Diagnosis is made through specialist multidisciplinary assessment, not by a single test or questionnaire.²

• Detailed developmental history from birth, including early social, language and play development - a parent or carer account is essential in children and highly valuable in adults
• Direct observation and interaction across settings, with information from school or workplace
• Structured tools - ADOS-2 (observational) and ADI-R (caregiver interview) are the standard instruments; AQ-10 is a brief screening tool that indicates whether referral is warranted but never diagnoses
• Cognitive and language assessment by psychology and speech and language therapy, to characterise the profile and identify intellectual disability
• Hearing assessment for every child being assessed
• Physical examination for dysmorphic features, neurocutaneous stigmata (tuberous sclerosis, neurofibromatosis) and head circumference
• Genetic testing - chromosomal microarray and fragile X testing are considered, particularly where there is intellectual disability, dysmorphism or a family history
• No routine imaging or EEG unless seizures or focal neurology are suspected

Management

There is no medical treatment for the core features of autism. Management centres on adapting the environment, supporting communication and functioning, and identifying and treating comorbid conditions - which is where most of the modifiable distress actually lies.³

Support and adaptation

• Speech and language therapy - supporting communication, including augmentative and alternative communication such as PECS or communication devices for those with limited speech
• Occupational therapy - sensory assessment and strategies, and support with daily living skills
• Educational support - an EHC plan assessment where needed, with adjustments such as predictable routines, visual timetables, advance warning of changes, quiet spaces and reduced sensory load
• Parent and carer training and support, focused on understanding communication and sensory needs rather than on eliminating autistic behaviours
• Structured social skills support where the individual wants it - offered as an option, not imposed
• Transition planning into adulthood, employment support and social care assessment where needed⁴

Medication

• No medication treats the core features of autism
• Treat comorbidity on its own merits - SSRIs for anxiety or depression, ADHD medication where ADHD coexists, antiepileptics for epilepsy. Autistic people are often more sensitive to side effects, so start low and go slow.
• Antipsychotics (risperidone, aripiprazole) may be considered short-term for severe, persistent challenging behaviour that has not responded to psychosocial intervention, but only after the cause of the behaviour has been sought - pain, constipation, dental problems, sensory overload and communication frustration are frequent and treatable drivers
• Melatonin for persistent sleep problems where sleep hygiene has been optimised

Reasonable adjustments in healthcare

Autistic people have markedly worse health outcomes and a substantially reduced life expectancy, driven in large part by barriers to accessing healthcare rather than by autism itself. Making adjustments is a legal duty under the Equality Act 2010, and is straightforward in practice.

• Offer the first or last appointment of the day to minimise waiting, and provide a quiet waiting area
• Communicate clearly and literally - avoid metaphor and vague phrasing such as 'this might sting a little'; say precisely what will happen and for how long
• Explain before touching, and ask permission for each part of an examination
• Allow extra time, and permit written responses or a supporter to speak if preferred
• Reduce sensory load - dim lighting, minimise noise, allow the person to keep ear defenders or a comfort object
• Ask the person or their carer what helps - many have a hospital passport documenting their needs and communication preferences

Prognosis

Autism is lifelong, and the aim is not remission but good quality of life with appropriate support. Outcomes vary enormously across the spectrum: many autistic adults live independently, work and maintain relationships, particularly where their strengths are recognised and their environment accommodates their needs, while those with co-occurring intellectual disability or limited speech may require lifelong support.

Better outcomes are associated with early identification, effective communication support, treatment of comorbid mental and physical illness, and - importantly - acceptance and appropriate adjustment rather than pressure to appear neurotypical. Mental health outcomes remain a serious concern: rates of anxiety, depression and suicide are substantially elevated, and this is strongly linked to masking, social exclusion, unemployment and poor access to appropriate services rather than to autism itself. That distinction matters, because it identifies what is actually modifiable.