Guide ยท Child development
Global developmental delay: what it means and what happens next
A paediatrician has written "global developmental delay" on a letter about your child. This is what the term means, what it doesn't mean, and what usually happens next in Australia.
Updated 5 October 2026 · About 11 minutes to read · All guides
In short
- Global developmental delay (GDD) means a child under 5 is significantly behind in at least two areas of development: movement, speech and language, thinking, social skills or everyday skills.
- It describes where a young child is now, not a lifelong diagnosis. Some children catch up, some keep having delays, and some are later diagnosed with intellectual disability, autism or a specific language disorder.
- GDD affects about 1 to 3% of children under 5. A cause, often genetic, is found in some; in many it isn't, even after testing.
- In Australia the path is usually GP or child health nurse, then paediatrician, with hearing and vision checks, sometimes genetic tests, and therapy as needed.
- Children younger than 9 can get help through the NDIS early childhood approach and, from October 2026, Thriving Kids, without a diagnosis. GDD itself is on the NDIA's List D, which means a child under 7 with the diagnosis meets the early intervention requirements without further assessment.
What global developmental delay means
Global developmental delay (GDD) is the term paediatricians use when a child under 5 is significantly behind in at least two areas of development. It describes where a young child is now, at an age when the tests used to diagnose intellectual disability can't yet be done. It is not a lifelong label.
The areas of development
The Canadian Paediatric Society's 2026 statement and a 2017 review in Archives of Disease in Childhood list five:
- Gross and fine motor: sitting, walking, using the hands
- Speech and language
- Cognition: thinking, problem solving, learning
- Social and personal: interacting with people, play
- Activities of daily living: feeding, dressing, toileting for the child's age
A delay in one area only, such as speech, is not GDD.
What "significant" means
Usually a score at least 2 standard deviations below the average for the child's age on a standardised developmental test, roughly the lowest 2 to 3%. The Canadian statement notes there is no universally agreed cut-off.
The DSM-5-TR, the diagnostic manual used in Australia, treats GDD as its own diagnosis, separate from intellectual disability and autism. Because it is reserved for children under 5, the Canadian Paediatric Society says a formal assessment for intellectual disability should be considered later in childhood or adolescence, so supports and eligibility for services continue.
How common it is, and what causes it
GDD is estimated to affect 1 to 3% of children under 5. Developmental delay of any kind is more common, at around 10 to 15% of preschool children.
Causes
- Genetic: chromosome conditions such as Down syndrome, single-gene conditions such as fragile X (about 1 in 5,000 births), and small missing or duplicated pieces of chromosome (copy number variants).
- Before birth: alcohol or some drugs in pregnancy, and infections passed to the baby.
- Around birth: prematurity, and lack of oxygen around delivery.
- After birth: brain infections such as meningitis, head injury, poor nutrition, and neglect.
Raising Children Network adds physical illness, time in hospital and family stress, and says in many cases the cause isn't known. In the 2017 review, history and examination identified the cause in about a third of children and targeted tests in roughly another third.
Tests your paediatrician may suggest
- Hearing and vision checks for every child with suspected GDD.
- Chromosomal microarray, a blood test for missing or extra pieces of chromosome and the recommended first genetic test when nothing else points to a cause. It finds an answer in roughly 15 to 20% of children.
- Fragile X testing for moderate to severe GDD, or where features or family history suggest it.
- Metabolic tests on blood and urine, now reserved for children with additional neurological or metabolic features because the yield is low.
- Exome sequencing as a second step, which finds a cause in about 26 to 31% of children in studies.
- Brain MRI only with specific findings such as a small head, abnormal neurological signs or loss of skills; targeted scans find an abnormality in about 41% of children, against 14% when all are scanned.
A diagnosis can give parents an explanation and stop the move to more invasive tests. Not finding one is common, and support does not depend on it.
GDD, intellectual disability, autism and single-area delays
These terms get mixed up, including on letters.
| Term | What it means | Age | How it is decided |
|---|---|---|---|
| Global developmental delay | Significant delay in two or more areas of development | Under 5 | History, examination and usually a developmental assessment; reviewed as the child grows |
| Intellectual disability | Lifelong limits in both intellectual and everyday (adaptive) functioning | Once formal testing is possible, in childhood or adolescence | A psychologist's IQ test plus an adaptive functioning measure; both required |
| Autism | Lifelong differences in social communication and in repetitive behaviours, interests and sensory responses | Any age | Pattern of social communication and behaviour against DSM-5-TR criteria |
| Single-area delay, such as language | Slower in one domain while the others are on track | Early childhood | Assessment of that area, plus a hearing test for language delay |
How they relate
Intellectual disability and GDD describe the same kind of difficulty at different ages. Under 5 the term is GDD; once a child can sit a standardised intelligence test, the question becomes whether intellectual disability is present. The American Psychiatric Association puts intellectual disability at about 1% of the population, about 85% of it mild.
Autism is a different kind of difference, in how a child communicates and relates. A child can have GDD, autism, both or neither. The DSM-5-TR autism criteria require that the social communication differences are not better explained by intellectual disability or GDD, and note that autism and intellectual disability frequently co-occur. See signs of autism in children.
What happens over time
Outcomes vary. In a Montreal cohort, 48 children diagnosed with GDD at about 3 were reassessed at about 7: 75 to 100% still scored at least 1.5 standard deviations below average on each developmental domain. A 2009 Canadian study cited by the Canadian Paediatric Society found 73% of children later scored an IQ of 70 or above, so most did not meet the intellectual criterion for intellectual disability. A 2023 study in the same statement found children scoring 2 or more standard deviations below the mean on the Griffiths scales at 2 to 3 had an 86% likelihood of testing in the intellectual impairment range at 4 to 6.
So a significant delay on formal testing at 2 to 3 often persists, the label on its own does not predict intellectual disability, and every child with GDD needs follow-up. Language delay alone is different: Raising Children Network says about 1 in 3 two-year-olds show signs of it and most late talkers have caught up by 4, though it can also be a sign of hearing loss.
How assessment works in Australia
The path usually starts with your GP or child and family health nurse, who can assess your child and refer to a paediatrician. The Sydney Children's Hospitals Network describes the first steps: questions about your child's health and development, a physical check, and playing and talking with your child.
Developmental assessment tools
- Bayley-4, for children from 16 days to 42 months, covering cognitive, language, motor, social-emotional and adaptive development.
- Griffiths III, a play-based measure of development from birth to 6 years.
- Vineland-3, a measure of adaptive functioning (communication, daily living skills and socialisation) based on a parent or carer interview or form. The NDIA names it as a preferred measure of everyday functioning.
Intelligence tests exist for young children (the WPPSI-IV starts at 2 years 6 months), but the Canadian Paediatric Society describes children under 5 as too young for the tests used to diagnose intellectual disability. When a child is older, a cognitive and intellectual disability assessment by a psychologist combines an IQ test with a structured adaptive functioning measure; both are needed for a diagnosis to stand up.
Raising Children Network lists the professionals families may then work with: audiologists, occupational therapists, optometrists, physiotherapists, psychologists, social workers, special education teachers and speech pathologists.
The NDIS, Thriving Kids and developmental delay
The NDIS now
For children younger than 9, the NDIS works through early childhood partners: local teams that offer early connections to supports and can help even if a child isn't eligible for the NDIS.
For a child younger than 6, the NDIS can be accessed under the early intervention requirements on the basis of developmental delay rather than a named condition. The NDIA's guideline defines it as a delay in one or more of self-care, language, cognitive or motor development that substantially reduces the child's functional capacity compared with other children the same age, and means the child needs services from more than one professional working as a team, usually for longer than 12 months. Global developmental delay is on the NDIA's List D: conditions for which a child younger than 7 is taken to meet the early intervention requirements once there is evidence of the diagnosis, with no further assessment of the impairment needed. Intellectual disability, when assessed as moderate, severe or profound, is on List A, which works the same way for the disability requirements. Our guide to how the NDIS works explains the lists and evidence.
Thriving Kids
From October 2026, Thriving Kids supports children aged 8 and under with developmental delay and/or autism with low to moderate support needs, outside the NDIS. No diagnosis is needed. From 1 January 2028, children in that group will be supported by Thriving Kids instead of the NDIS, while children with high support needs or permanent and significant disability stay eligible. Children already in the NDIS before then continue to be reassessed under the earlier rules. Our Thriving Kids guide has the detail. Nobody can promise an NDIS outcome.
Does early intervention help?
Australian health services say yes. Raising Children Network says children who get early intervention might need less or no support as they get older, and the Sydney Children's Hospitals Network says the earlier children get support, the better the outcomes.
The trial evidence is strongest for babies born preterm. A 2024 Cochrane review of 44 randomised trials (5,051 infants) found early developmental intervention improved cognitive outcomes at preschool age (high-certainty evidence, about 0.4 of a standard deviation), may improve cognitive and motor outcomes in infancy (low-certainty evidence), and had no clear effect on cognition at school age. A real but modest effect, in one population; evidence for GDD from other causes is thinner, so be cautious about promises. Support does not have to wait for a cause or a diagnosis.
What you can do now
- Check the milestones, without panicking over one. Pregnancy, Birth and Baby publishes milestone guides by age. Raising Children's rule of thumb: be concerned if, over several months, your child isn't developing skills at the same rate as other children the same age.
- Keep a record. Keep every report together. Your child's personal health record (the Blue Book in NSW) tracks development to age 5, and both the NDIS and Thriving Kids look at how your child manages day to day.
- Get hearing and vision checked if they haven't been.
- Act quickly on lost skills. The BMJ's review on developmental assessment says a child losing abilities they had needs urgent specialist evaluation, and that parental concerns warrant serious consideration.
If you are also wondering about autism, our free screener (choose "My child") suggests whether an assessment is worth considering, and will say if one does not look like the right next step. It is not a diagnosis or a developmental assessment.
Questions people ask
What is global developmental delay in simple terms?
Global developmental delay means a child under 5 is significantly behind other children their age in at least two areas of development, such as movement, talking, thinking or everyday skills. It describes where a child is now, not what they will be like for life.
Is global developmental delay the same as autism?
No. GDD means broad delays across two or more areas of development in a child under 5. Autism is a lifelong difference in social communication and in behaviour, interests and sensory responses. A child can have GDD without being autistic, be autistic without GDD, or have both.
Is global developmental delay the same as intellectual disability?
No, but they are related. GDD is the term for children under 5, who are too young for the formal IQ testing that intellectual disability needs. Some children with GDD are later diagnosed with intellectual disability and many are not, so a formal reassessment later in childhood is recommended.
Can a child grow out of global developmental delay?
Some do. In a Canadian study cited by the Canadian Paediatric Society, 73% of children diagnosed with GDD later scored an IQ of 70 or above. But delays often persist: in a Montreal cohort followed to about 7, most children still scored well below average.
Does global developmental delay qualify for the NDIS?
It can. Global developmental delay is on the NDIA's List D, so a child younger than 7 with evidence of the diagnosis is taken to meet the early intervention requirements without further assessment of the impairment. For a child younger than 6 without that diagnosis, the early intervention requirements ask for evidence that developmental delay substantially reduces your child's functional capacity and that your child needs a team of professionals for longer than 12 months. From 1 January 2028, children aged 8 and under with low to moderate support needs will be supported by Thriving Kids instead.
At what age is global developmental delay diagnosed?
GDD is a term for children under 5, usually recognised in the toddler and preschool years when a child is clearly behind in more than one area. After about 5, when formal testing becomes possible, a psychologist can assess whether intellectual disability is present.
Wondering whether an assessment makes sense? The free screener takes about three minutes, for your child, your adult son or daughter, or yourself. It suggests which assessment fits, and it will tell you if one does not look like the right next step. Start the free screener.
Where this information comes from
We would rather you checked us than took our word for it. Every link below is the original source, not a summary of one.
- McLeod et al. (2026). Assessing children and youth with global developmental delay and intellectual developmental disorder. Paediatrics & Child Health.Canadian Paediatric Society position statement: GDD defined as significant delay in at least two domains in children under 5, hearing and vision checks for all, microarray first, exome sequencing yield, MRI only with specific signs, and the 2009 and 2023 outcome studies.
- Mithyantha et al. (2017). Current evidence-based recommendations on investigating children with global developmental delay. Archives of Disease in Childhood.UK review of guidelines on investigating GDD: the five domains, 2 SD definition, 1 to 3% prevalence, causes, and the yields of microarray, fragile X, metabolic tests and MRI.
- Shevell et al. (2005). Developmental and functional outcomes at school age of preschool children with global developmental delay. Journal of Child Neurology.Montreal cohort of 48 children diagnosed with GDD at about 3 and reassessed at about 7, most still scoring well below average across developmental and adaptive domains.
- Choo et al. (2019). Developmental delay: identification and management at primary care level. Singapore Medical Journal.Primary-care review giving the 2 SD definition of significant delay, 10 to 15% prevalence of any developmental delay and 1 to 3% for GDD, and hearing and vision assessment.
- Orton et al. (2024). Early developmental intervention programmes provided post hospital discharge to prevent motor and cognitive impairment in preterm infants. Cochrane Database of Systematic Reviews.Cochrane review of 44 randomised trials (5,051 preterm infants) finding improved cognitive outcomes at preschool age, probable benefit in infancy, and no clear effect at school age.
- Patel et al. (2020). A clinical primer on intellectual disability. Translational Pediatrics.Review of the DSM-5 criteria for intellectual disability (intellectual and adaptive deficits with onset in the developmental period), 1 to 3% prevalence, and that a cause is found far more often in severe than mild intellectual disability.
- Bellman et al. (2013). Developmental assessment of children. BMJ.BMJ clinical review whose summary points state that parental concerns about development warrant serious consideration and that loss of previously learned skills requires urgent specialist evaluation.
- Raising Children Network (2026). Developmental delay.Australian government-funded parenting site: definition of developmental and global developmental delay, causes, when to be concerned, who to see, the professionals involved, early intervention, Thriving Kids and the NDIS.
- Raising Children Network (2025). Language delay in children.About 1 in 3 two-year-olds show signs of language delay, most late talkers catch up by 4, and language delay can be a sign of hearing loss.
- Raising Children Network (2026). Thriving Kids: FAQs about support, eligibility and access.Who Thriving Kids is for, that no diagnosis is needed, how supports are reached, and the change from 1 January 2028.
- Sydney Children's Hospitals Network (2026). Developmental delay factsheet.NSW Health children's hospitals factsheet: what developmental and global developmental delay mean, risk factors including Down syndrome and prematurity, what an assessment involves, the Blue Book, referrals, and that earlier support is linked to better outcomes.
- Sydney Children's Hospitals Network (2026). Intellectual disability factsheet.Intellectual disability as a lifelong condition identified by a psychologist using formal tests, its causes, its relationship to global developmental delay in children under 5, and the NDIS.
- Autism Aspergers Advocacy Australia (A4). Autism Spectrum Disorder (ASD) in the DSM-5-TR.Reproduction of the DSM-5-TR autism criteria, including criterion E (not better explained by intellectual disability or global developmental delay), the note that autism and intellectual disability frequently co-occur, and the 'with or without accompanying intellectual impairment' specifier.
- American Psychiatric Association. What is intellectual disability?Intellectual disability affects about 1% of the population (2 to 3% of children in high-income countries), about 85% mild; an IQ around 70 to 75 and adaptive skills 2 SD below the norm (below roughly the 2nd to 3rd percentile).
- NDIS. What are the early intervention eligibility requirements?For children younger than 6: developmental delay due to impairments that substantially reduces functional capacity and requires more than one professional working as a team for longer than 12 months.
- National Disability Insurance Agency (2026). Applying to the NDIS (guideline dated 26 August 2026).The NDIA's access guideline, including List A (conditions taken to meet the disability requirements), List B, and List D (conditions for which a child under 7 is taken to meet the early intervention requirements, which includes global developmental delay).
- NDIS. Guide to the early childhood approach.Early childhood partners for children younger than 9, early connections, and help for children with developmental concerns even if they aren't eligible for the NDIS.
- NDIS. What are examples of disability evidence?For intellectual disability the NDIA accepts evidence from a paediatrician, psychologist, occupational therapist or speech therapist and prefers the DSM-5, the Vineland-III and the WHODAS 2.0 or PEDI-CAT.
- Department of Health, Disability and Ageing. About Thriving Kids.Who Thriving Kids is for, that no diagnosis is needed, the rollout from October 2026 to 1 January 2028, and that NDIS access doesn't change before then.
- Department of Health, Disability and Ageing (2026). About the changes to the NDIS.From 1 January 2028, children aged 8 and under with developmental delay and/or autism and low to moderate support needs move to Thriving Kids, children with high support needs stay eligible, and children already in the NDIS are reassessed under the earlier criteria.
- Pearson. Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4).Publisher's description: ages 16 days to 42 months, covering cognitive, language, motor, social-emotional and adaptive behaviour domains.
- Association for Research in Infant and Child Development. About the Griffiths Scales.The Griffiths III as a play-oriented measure of development from birth to 6 years.
- Pearson. Vineland Adaptive Behavior Scales, Third Edition (Vineland-3).Publisher's description: adaptive functioning across communication, daily living skills and socialisation, from birth, by parent or caregiver interview or form, with a teacher form for ages 3 to 21.
- Pearson. Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition (WPPSI-IV).Publisher's description: an intelligence test for ages 2 years 6 months to 7 years 7 months.
- Pregnancy, Birth and Baby (Healthdirect Australia). Children development and milestones.Government-funded hub of developmental milestone guides by age from 12 months to 5 years, with pages on developmental delay and regression.
Links to external sites are provided for reference. We do not control them and they may change. Last checked 5 October 2026.
This guide is general information, not medical advice. If you are worried about yourself or your child, talk to your GP.
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