Autism Spectrum Disorder

See also developmental assessment and behavioural problems in childhood.

DSM-5 diagnostic criteria (299.00)

1. Persistent deficits in social communication/interaction across multiple contexts — social-emotional reciprocity (abnormal social approach, failure of back-and-forth conversation, reduced sharing of interests/emotion, failure to initiate/respond to social interaction); nonverbal communicative behaviours (poor integration of verbal/nonverbal communication, abnormal eye contact/body language, deficits in gesture); and difficulties developing/maintaining/understanding relationships (adjusting behaviour to context, sharing imaginative play, making friends, or absent interest in peers).
2. Restricted, repetitive patterns of behaviour/interests/activities (≥2 of): stereotyped/repetitive motor movements, object use or speech (motor stereotypies, lining up toys, echolalia); insistence on sameness/ inflexible routines (distress at small changes, rigid thinking, ritual greetings); highly restricted, fixated interests abnormal in intensity/ focus; hyper- or hypo-reactivity to sensory input (indifference to pain/ temperature, adverse response to sounds/textures, sensory-seeking behaviours).
3. Symptoms present in the early developmental period (may not fully manifest until social demands exceed capacity, or may be masked by learned strategies later).
4. Symptoms cause clinically significant functional impairment.
5. Not better explained by intellectual disability/global developmental delay (though they frequently co-occur — for a comorbid diagnosis, social communication must be below what’s expected for the general developmental level).

DSM-5 (May 2013) replaced autistic disorder, PDD-NOS and Asperger disorder with the single “autism spectrum disorder” label (though “Asperger’s” is still widely used colloquially), collapsing the old three-domain model (social/communication/repetitive behaviour) into two, and adding a severity scale: level 3 (very substantial support), level 2 (substantial support), level 1 (some support).

Epidemiology

Australian prevalence has risen substantially in successive surveys — not because underlying incidence has changed, but reflecting broadened DSM-5 criteria, improved recognition and greater service access (including the NDIS). 4.3% of people aged 5–14 years were autistic in 2022, up from 3.2% in 2018.

Global prevalence estimates are lower than Australia’s and vary widely by country, reflecting differences in diagnostic methods, populations surveyed and service availability — a pooled meta-analysis found prevalence of 1.01% in North America, 0.73% in Europe and 0.41% in Asia, with global point-prevalence roughly quadrupling from 0.25% (1994–1999) to 0.99% (2015–2019). Boys are diagnosed roughly four times as often as girls; autism in girls/women is more often under- or later-diagnosed, partly because of “camouflaging” (below).

Identification

Three typical scenarios: a parent raises their own concern; a parent relays a third party’s concern (childcare worker, teacher); or the GP identifies concerns via routine developmental screening/observation.

When to suspect ASD — typical joint-attention milestones: smiling back at a caregiver by 2–4 months; following a parent’s gaze by 8 months; following a point by 10–12 months and pointing themselves by 12–14 months; pointing to share (look at this”) by 16 months, looking back and forth between object and parent. “These joint-attention behaviours are often absent or reduced in ASD.

Social deficits

Younger children may show little desire to connect; difficulty imitating actions (e.g. clapping). Older children/adults struggle with theory-of-mind (understanding others’ perspectives), affecting empathy and sharing. Few/no friends, or inappropriate approaches to peers; inappropriate comments (e.g. on appearance); can become overwhelmed by social/sensory stimulation.

Communication deficits

Deficits in verbal and non-verbal, expressive and receptive language — some remain non-verbal. Language may be rote (shapes/numbers) without being functional (can’t follow one-step commands). Echolalia (parroting learned phrases) is common; unusual vocal tone/speed; pronoun reversal. Very literal understanding of language — idioms, lies, jokes, body language and tone often missed. Play is often unusual and repetitive (lining up toys, spinning wheels) rather than imaginative, and object-focused rather than people-focused; limited interest in social games (peek-a-boo).

Recognising undiagnosed autism in adults

Autistic adults — including some already misdiagnosed with a personality disorder, depression or intellectual disability, or previously labelled with the now-retired Asperger’s” diagnosis — commonly reach a GP consultation without ever being identified. “Many “do their best to fit the expectations of how a patient should behave” — smiling, making eye contact, being overly polite — a subconscious effort called camouflaging or masking, which is why autism can be very hard to spot in a short consultation and is a particular reason autistic girls/women are under-recognised. Useful clues: a history of heightened sensory sensitivity (lights, sounds, textures, smells) causing fatigue after socialising; difficulty with executive function (missed appointments, disorganisation) not explained by a busy life alone; a childhood/teenage history of bullying, burnout or not “fitting in”; and family members (including children) with autism or ADHD.

Co-occurring conditions to consider in an autistic (or possibly autistic) adult: anxiety, depression, ADHD, migraine with aura, eating disorders/food sensitivities, PTSD, sleep apnoea, GI disorders, epilepsy, hypermobility spectrum disorders/Ehlers-Danlos syndromes, fibromyalgia and OCD. Autistic people have a nine-fold increased risk of suicidality, and the average life expectancy of an Autistic person is 54 years, well below that of the general population.

Practical GP accommodations: use strengths-based, non-deficit language; give the patient time to answer without “reading between the lines”; avoid analogies/irony/sarcasm; offer a quiet place to wait; allow longer or online appointment booking; be understanding of missed appointments; support formal autism assessment if the patient wants it (usually by a psychologist/psychiatrist experienced with adult, and particularly female, presentations — availability and cost are recognised barriers in Australia).

Red flags — absolute indications for autism-specific referral

Lack of babbling, gesturing or pointing by 12 months; no sharing of interest in objects/activities with another person; no single words by 16 months, or no (non-echoed) two-word phrases by 24 months; any loss of language or social skills at any age.

Screening tool

CHAT (abbreviated) at ~18 months (a couple of minutes to administer):

Ask the parent	GP observation
Does your child ever pretend (e.g. make tea with a toy cup)?	Give a toy cup/teapot: “can you make a cup of tea?” — does the child pretend to pour/drink?
Does your child point with the index finger to ask for something?	Point at an object across the room and say “oh look!” — does the child look at the object (not just your hand)?
	”Where’s the light?” — does the child point with the index finger, looking up at your face around that time?

Fail all 3 items → high chance of autism, refer. Fail 1–2 items → still refer, high chance of developmental delay.

Further assessment

Prompt referral to a general or developmental paediatrician, or a developmental assessment unit, is essential — a “wait and see” or “come back in 6 months” approach is not acceptable. Hearing checks and speech pathology/OT/psychology assessments can run in parallel.

There are no laboratory tests or scans that diagnose ASD — it is a clinical diagnosis made by a trained clinician integrating history and structured behavioural observation, ideally using a validated tool such as the Autism Diagnostic Observation Schedule (ADOS-2). A full evaluation covers past medical/developmental/social/family history, a complete physical examination (growth parameters, neurological exam, dysmorphic features), and hearing and vision testing; consider referral for genetic evaluation, and reserve neuroimaging/EEG/metabolic work-up for atypical regression, seizures, an abnormal neurological exam, or cranial/growth abnormalities rather than ordering them routinely.

Comorbidities

Comorbidity is the rule, not the exception — one study found 74% of young people with ASD had at least one comorbidity (another found 74% had at least five). Reported rates in children/adolescents with ASD include ADHD (28%), anxiety disorders (20%), sleep–wake disorders (13%), disruptive/impulse-control/conduct disorders (12%), depressive disorders (11%), OCD (9%), bipolar disorder (5%) and schizophrenia-spectrum disorders (4%). Around 30% of children with ASD have an intellectual disability and 30% are minimally verbal. Physical comorbidities are also common: motor abnormalities (~79%), gastrointestinal problems (up to 70%), sleep disorders (50–80%) and epilepsy (up to 30%). A change in behaviour should always prompt a check for an undiagnosed physical cause (dental pain, reflux, otitis media, fracture, constipation) before it is attributed to autism itself.

Children with autism have particular vulnerability to: minor trauma/injury, restricted diet (sensory issues or special diets), behavioural issues, constipation (sensory-driven voluntary retention, or medication side effects), and dental issues (sensory-related brushing difficulty, or teeth grinding).

Management

Early intervention

Intensive early intervention is the guideline gold standard and improves long-term outcomes — earlier is better — but can be beyond a family’s organisational/financial capacity, so tailor recommendations accordingly. The evidence base for the best-studied model, early intensive behavioural intervention (EIBI, 20–40 hours/week over multiple years, based on applied behaviour analysis), supports improved adaptive behaviour, IQ and expressive/receptive language after around two years of treatment, but a Cochrane review rates this “weak evidence” — only one of the five trials it examined used random allocation, and EIBI did not show a significant effect on autism symptom severity itself or on problem behaviour. Direct parents to reliable information sources (there is a lot of misinformation, especially around unproven complementary/ alternative therapies). State autism associations can help; if waiting times for diagnostic assessment are long, refer to early intervention services in the meantime.

Pharmacological management

No medication treats the core symptoms of autism (social communication deficits, restricted/repetitive behaviour) — non-drug therapies remain first-line, particularly under 7–8 years. Drug treatment has a role only for specific comorbid/target symptoms, once any underlying medical cause of a behaviour change has been excluded, and polypharmacy should be avoided where possible.

• Irritability and aggression: risperidone and aripiprazole are the best-evidenced options; risperidone is TGA-approved for irritability and aggression in autism under 18 years. Adverse effects (weight gain, raised lipids/prolactin/glucose, pubertal disruption) require baseline monitoring (weight, fasting lipids, glucose, prolactin — and menarche/ menstrual regularity where relevant) before starting, repeated at one month and then six-monthly. Antipsychotics should only be started by, or in consultation with, a psychiatrist or paediatrician.
• Anxiety (the most common psychiatric comorbidity): cognitive behaviour therapy first, with an SSRI (sertraline, fluoxetine or fluvoxamine) considered when anxiety is functionally impairing (school avoidance, loss of friendships) — start at low dose with slow titration; monitor for increased suicidal thinking in the first two weeks.
• Comorbid ADHD: treated with the same drugs used for ADHD alone (methylphenidate, dexamfetamine, atomoxetine, guanfacine).
• Tics/Tourette syndrome: clonidine first-line; aripiprazole an alternative if there is little response to, or a contraindication to, clonidine.
• Insomnia (affects up to ~80% of people with ASD): behavioural management is the mainstay. Benzodiazepines and antipsychotics should be avoided for sleep because of their adverse-effect burden; melatonin is commonly used, with a low risk of dependency, and low-dose clonidine (50–200 micrograms at night) is an option when insomnia follows stimulant treatment.

The GP’s ongoing role

The GP’s ongoing role: monitor family coping, provide a reliable “medical home”. A regular review is worthwhile even for a patient who hasn’t presented in a while — absence of contact doesn’t mean all is well, and it is an opportunity to keep preventive care (and comorbidity screening, above) on track.