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# Autism spectrum disorder (ASD)

Autism is a lifelong developmental condition that affects social communication and causes restricted, repetitive behaviours. Early support helps.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Amygdala](https://durgical.com/en/anatomy/amygdaloid-body/)
- [Cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/)
- [Temporal lobe](https://durgical.com/en/anatomy/middle-temporal-gyrus/)
- [Frontal lobe](https://durgical.com/en/anatomy/superior-frontal-gyrus/)
- [Vermis](https://durgical.com/en/anatomy/central-lobule/)
- [Corpus callosum](https://durgical.com/en/anatomy/corpus-callosum/)

## In embryology

- [Valproate, carbamazepine and phenytoin](https://durgical.com/en/embryology/valproate-carbamazepine-and-phenytoin/)

## In the clinical exam

- [Pediatric history: perinatal, growth, development and vaccines](https://durgical.com/en/clinical-exam/pediatric-history-perinatal-growth-development-and-vaccines/)

## Why it happens

- [Nonclassic inheritance: repeat expansions, mitochondrial genes, imprinting, mosaicism](https://durgical.com/en/general-pathology/nonclassic-inheritance-repeat-expansions-mitochondrial-genes-imprinting-mosaicis/)

## What it is

A neurodevelopmental disorder defined by persistent deficits in social communication and interaction plus restricted, repetitive patterns of behaviour, interests or activities, present from early childhood. Its severity and the support each person needs vary widely, hence 'spectrum'.

## Who gets it

Estimated to affect about 1 in 100 children worldwide, with higher figures in countries with active screening. It is diagnosed about four times more often in boys. In Colombia and Latin America diagnosis is often late, and access to early intervention is uneven.

## Causes

- Strong genetic basis: many genes and copy-number variants
- Syndromic forms: fragile X syndrome, tuberous sclerosis, Rett syndrome
- Prenatal factors: valproate exposure, maternal infection such as rubella
- Vaccines do NOT cause autism

## Risk factors

- Sibling with autism
- Male sex
- Older parents
- Prematurity and very low birth weight
- Untreated phenylketonuria and other genetic syndromes

## Pathophysiology

Brain development differs from very early on: atypical growth in the first years, altered connectivity between distant regions, and differences in networks for social perception ([amygdala](https://durgical.com/en/anatomy/amygdaloid-body/), [temporal lobe](https://durgical.com/en/anatomy/middle-temporal-gyrus/), fusiform face area), language and the [cerebellum](https://durgical.com/en/anatomy/anterior-quadrangular-lobule/). An imbalance between excitation and inhibition in cortical circuits is thought to underlie sensory hypersensitivity and repetitive behaviour.

## Classification

- Level 1: requiring support
- Level 2: requiring substantial support
- Level 3: requiring very substantial support
- Specifiers: with or without intellectual or language impairment; associated with a known genetic condition

## Symptoms and signs

- Little eye contact, no response to name, lack of pointing to share interest or of joint attention
- Language delay, echolalia or unusual tone; difficulty with back-and-forth conversation
- Difficulty understanding emotions and making friends; little pretend play
- Repetitive movements (hand flapping, rocking), lining up objects, insistence on sameness and distress at change
- Highly restricted, intense interests and over- or under-reaction to sounds, textures or pain

## Red flags

- Any loss of language or social skills at any age
- No babbling or gesturing by 12 months, no single words by 16 months or no two-word phrases by 24 months
- Seizures (epilepsy is more common in autism)
- Self-injury, aggression or sudden behaviour change, which may signal unrecognised pain or illness

## Diagnosis

**Clinical**
Developmental surveillance at every well-child visit and standard autism screening (e.g. M-CHAT-R/F) at 18 and 24 months; positive screens go to a multidisciplinary assessment using DSM-5-TR criteria, supported by structured tools such as ADOS-2.

**Tests**
Formal hearing test in every child; genetic testing (chromosomal microarray and fragile X testing) is recommended. EEG if seizures are suspected; metabolic tests (e.g. for phenylketonuria) when the history suggests them.

**Imaging**
Not routine. Brain MRI only with neurological signs, abnormal head size or regression.

## Differential diagnosis

- Hearing loss
- Developmental language disorder
- Intellectual disability without autism
- Rett syndrome (girls with regression and hand-wringing)
- Reactive attachment disorder after severe neglect

## Goal of treatment

Maximise communication, social and daily-living skills and independence through early, intensive, individualised intervention; support families; and treat coexisting conditions. Autism itself is not 'cured'.

## Treatment

**Rehabilitation**
Early intensive behavioural and developmental interventions (e.g. applied behaviour analysis, naturalistic developmental approaches), speech and language therapy, and occupational therapy for sensory and motor needs.

**Conservative**
Inclusive education with individual support plans, social skills training and parent training.

**Medical**
No drug treats the core features. Second-generation antipsychotics (risperidone, aripiprazole) are used for severe irritability and aggression; other drugs treat coexisting ADHD, anxiety, sleep problems or epilepsy.

**Follow-up**
On antipsychotics: weight, waist, glucose and lipids. Nursing care adapts routines, reduces sensory overload and uses visual supports during procedures.

## Complications

- Epilepsy
- Anxiety, depression and ADHD
- Sleep and feeding problems (very selective eating)
- Wandering and drowning risk; injuries from self-harm
- Social isolation, bullying and caregiver burden

## Prognosis

Lifelong, but outcomes vary widely. Language before about age 5–6, higher cognitive ability and early intervention predict greater independence; many adults work and live independently, while others need lifelong support.

## Test yourself

Think of the answer, then tap the question to see it.

## What two core domains define autism spectrum disorder?

Persistent deficits in social communication and interaction, and restricted, repetitive behaviours, interests or activities.

## At what ages is standard autism screening recommended, and with which tool?

At 18 and 24 months, commonly with the M-CHAT-R/F.

## Which test should every child evaluated for autism have, and which genetic tests are recommended?

A formal hearing test; chromosomal microarray and fragile X testing.

## Which drug class is used for severe irritability in autism?

Second-generation antipsychotics such as risperidone or aripiprazole, with metabolic monitoring.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/conditions/autism-spectrum-disorder/)

## Related conditions

- [Attention-deficit/hyperactivity disorder (ADHD)](https://durgical.com/en/conditions/attention-deficit-hyperactivity-disorder/)
- [Obsessive-compulsive disorder (OCD)](https://durgical.com/en/conditions/obsessive-compulsive-disorder/)
- [Epilepsy and seizures](https://durgical.com/en/conditions/epilepsy-and-seizures/)
- [Phenylketonuria (PKU)](https://durgical.com/en/conditions/phenylketonuria/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Autism Spectrum Disorder](https://medlineplus.gov/autismspectrumdisorder.html) (MedlinePlus, US National Library of Medicine, 2025).

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Source: https://durgical.com/en/conditions/autism-spectrum-disorder/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/autism-spectrum-disorder/