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Learn The Difference Between Global Developmental Delay and Intellectual Disability

Around 20% of Australian children experience learning difficulties.

For some, it is a temporary concern that they outgrow as they get older. For others, it may be a more prominent developmental hindrance that requires ongoing support.

You may be wondering: Is developmental delay the same as intellectual disability?

In this article you will learn exactly how the two are connected, ways they differ, and what this means for NDIS support for your child. We discuss the importance of getting the right diagnosis and support to help your child best achieve their developmental goals.

Is Global Developmental Delay the Same as Intellectual Disability?

Global developmental delay (GDD) refers to children aged five years or younger who are delayed in achieving two or more developmental milestones. Children with GDD are at a higher risk for being diagnosed with an intellectual disability when they become older, though the two conditions do not necessarily go hand in hand.

The estimated prevalence of GDD is 1-3% of under five-year-olds [1], though having a global developmental delay does not guarantee an intellectual disability. Read on for a clinical definition of each separate condition.

Defining Global Developmental Delay

Global Developmental Delay is defined as the failure to achieve developmental milestones within the expected age range. GDD is categorised by a significant delay in two or more developmental domains. These domains include:

  • Speech and language
  • Motor skills
  • Cognition
  • Social and emotional development
  • Play skills

Children with global developmental delays often present as ‘behind’ the development of their peers. Some may describe affected children as ‘seeming younger’.

Infants and toddlers with global developmental delay who have delays involving nonverbal problem-solving and receptive language development are at significant risk for intellectual disability. The more severe the intellectual disability is, the younger the child can be at the time it is reliably identified [1].

It may take 6-12 months after initial concerns arise that GDD is diagnosed by a specialist. Developmental disabilities would typically be diagnosed by a paediatrician or a psychologist.

Early intervention promotes the best outcomes for children with global developmental delay as a child’s brain is most adaptive when they’re under three years old. Interventions implemented at this time have been proven to have a high chance of successful outcomes for the child.

Defining Intellectual Disability

What is intellectual disability?

Intellectual Disability is defined by a significant limitation in intellectual functioning (learning, reasoning and problem-solving) and adaptive functioning (communication, social and practical skills) that originates before 18 years [2].

An intellectual disability cannot be diagnosed until a child reaches an age, around six years old, when cognitive testing becomes valid and reliable.

GDD can be an indicator of intellectual disability, however comprehensive testing and a passage of time are needed to determine if this is the case [2].

For more information, you can read the Children With Disabilities Australia Publication here.

Can They Co-Exist?

Intellectual and developmental disabilities can occur in isolation or combination with each other and/or a range of other conditions including autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), epilepsy and more [1].

Yes, Global Developmental Delay and Intellectual Disability can co-exist: typically while awaiting a completely accurate diagnosis.

If multiple developmental delays are evident and severe, a diagnosis of intellectual disability may be given sooner.

Global Developmental Disorders refer to general delays that cannot be more specifically identified at the time of the assessment. GDD does not have a specific set of symptoms.

A child with GDD will be re-evaluated as they become older to obtain a more specific diagnosis. Those with a ‘mild’ diagnosis are the most likely to improve and no longer meet defining characteristics as they age [1]. Certain cognitive tests, such as IQ tests, can only be performed once the child reaches six years old.

Some children diagnosed with GDD can catch up to their expected developmental milestones and no longer meet the criteria for developmental delay as they get older.

Getting the Right Diagnosis

It is estimated that genetic causes account for approximately 40% of global developmental delays and intellectual disabilities [4].

A clinical assessment is typically recommended as the child becomes older, as a more accurate diagnosis is possible.

A comprehensive evaluation will involve:

  1. A detailed family history
  2. Current and past medical history
  3. Pregnancy and perinatal history
  4. Developmental and educational progress
  5. Physical examination
  6. Genetic testing and brain imaging if applicable

You can read about medical conditions that cause GDD and ID here.

Reasons for undertaking a diagnostic evaluation, which may include genetic testing, include:

  • To provide information to families about long-term complications
  • To create specific treatment options
  • To enable the families access to special education and support services
  • To provide the option for prenatal risk diagnosis to families

The NDIS Role with Developmental Delays and Intellectual Disabilities

The National Disability Insurance Scheme (NDIS) can link your child and family to support services to help your child achieve the best possible outcomes in their development, helping them to achieve their goals and potentially minimise the need for interventions in the future.

The NDIS can provide support to children with global developmental delay under the early intervention requirements until they turn 9 years old [3]. Children under six years old do not need a formal diagnosis to access supports.

Support services may include:

  • Speech therapy
  • Occupational therapy
  • Physiotherapy
  • Family support programs
  • Early Intervention programs

As children will usually have their GDD diagnosis re-evaluated around this time, they will either be determined to have “outgrown” their GDD diagnosis (that is, they have now caught up to their peers development level) or their diagnosis may change to an intellectual disability (or other condition). If this is the case, they may be eligible for NDIS support under the disability requirements.

Click here for more information about applying to the NDIS.

The earlier an accurate diagnosis is obtained, the greater the likelihood of positive clinical outcomes.

Early interventions are key to minimising barriers to engaging in daily life, improving cognitive ability, maximising function and promoting participation within the community.

What Supports Are Available?

Support is available from your child’s early childhood educators or school, your healthcare provider and within the community. You can also talk to an allied health professional for more information and help navigating the NDIS.

Allied health therapy providers can simplify the process for NDIS-funded participants and their families. Your key worker can coordinate your child’s therapy services and ensure they receive the services they need to develop their everyday skills. A key worker is one essential person your child and family can become familiar with and facilitate communication amongst the team of professionals supporting your child, which has been shown to significantly improve outcomes.

Find out more about the NDIS Developmental Delay and the Early Childhood Approach here.


Global developmental delay and intellectual disability are not the same thing, but they may be connected.

Global developmental delay is a general diagnosis given to children aged under 5 years where they fail to meet two or more developmental domains.

GDD may be indicative of an intellectual disability before an accurate, age-appropriate diagnosis.

An intellectual disability is a more specific diagnosis given to those exhibiting intellectual and adaptive functioning delays and who have undergone cognitive testing around age 6 (but before 18), when these tests are more reliable.

Having the right diagnosis can help you access the right supports, understand your child’s goals and potential complications. Support services are available to help you get the most out of your child’s NDIS funding, streamline therapies and improve outcomes.


[1] Access Paediatrics, 2017. Global Developmental Delay and Intellectual Disability.

[2] Vasudevan P, Suri M., 2017. A clinical approach to developmental delay and intellectual disability.

[3] NDIS, 2024. Developmental Delay and the Early Childhood Approach.

[4] Medical Home Portal, 2022. Intellectual Disability and Global Developmental Delay.

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