Intellectual Disability

Intellectual Disability is a developmental disability that affects people’s abilities in learning, processing information, communicating, socialising and sometimes physical skills.

Intellectual disability affects each person differently, and to different degrees, depending on many factors including the cause of the disability, family life, education opportunities, support systems and environmental factors. People may need assistance with everyday activities such as household tasks, organising daily activities, engaging socially with others, and managing money. Intellectual disability means that people may take longer to learn skills and gain knowledge or may need more specific explanations and support with how to do things or organise their lives and this lasts throughout their life. Some people with intellectual disability live fairly independently with supports from family and friends, whilst other people may need help with many aspects of their lives, including personal care, eating and drinking, and communication.

Intellectual disability can be caused by a genetic condition, illness or accident or the cause may be unknown. A person can be born with intellectual disability or acquire it before age 18. In Australia, around 2% of the population have intellectual disability.


Traditionally, intellectual disability is noticed when a child is not developing skills at the same rate as other children or is noticed by teachers at school. It may be formally diagnosed using three criteria:

  • Standardised tests of intelligence (testing a person's I.Q.).
  • Adaptive behaviour (a person’s ability to perform everyday activities, the ability to socialise and their skills in areas such as reading and writing).
  • Onset before the age of 18.

There are many names attached to different causes of intellectual disability including Down Syndrome, Fragile X syndrome, Prader-Willian Syndrome, Angelman Syndrome, Rett Syndrome, Tuberous sclerosis, Cri-du-chat Syndrome, Fetal Alcohol Spectrum Disorder, Williams Syndrome, Apert Syndrome, and Phenylketonuria (PKU), but still each person’s abilities and needs for support may be different.


Some of the areas where people with intellectual disability may need specific supports include:

  • Organising daily life activities such as when and where to go places, shopping, laundry, meal preparation and budgeting.
  • Organising and knowing when to go to self-care appointments such as the doctor or dentist.
  • Communication, social interaction, self-care and problem solving.
  • Practical skills that require literacy, time and number concepts.
  • Dealing with government systems, processes and agencies.
  • Understanding other people’s motives and therefore needing help with personal safety, advocacy to ensure their rights are upheld, and to safeguard their needs due to heightened social and emotional vulnerability.

However, the person’s needs and preferences for supports and what is actually helpful, will depend on many factors.

Some people with intellectual disability may also have “behaviours of concern” or “challenging behaviour” including behaviours where they harm themselves or be verbally or physically aggressive. These behaviours are usually a communication to others that the person is in need – of pain relief, reassurance, to feel safer, to feel secure in what is going to happen or what is happening, or maybe an expression of frustration, or need for attention, A behaviour support practitioner, psychologist, speech pathologist or occupational therapist may provide advice on communication and support to assist people with intellectual disability to be more easily able to communicate their needs; and for family members and other to be able to support the person in ways which are helpful to them.

Two girls, one with Downs syndrome, playing