What is an intellectual disability?

Key points

• Everyone with intellectual disability is different

• People with intellectual disability may think, learn or communicate differently

• Genetics, complications during pregnancy or birth, illnesses, exposure to drugs and alcohol or accidents and injury may cause intellectual disability

Somebody with intellectual disability may think, learn or communicate differently to others, which can pose challenges in relationship building, education, behaviour, inclusion and employment.

Intellectual disabilities can be genetic or caused by complications during pregnancy or birth, through some illnesses, exposure to alcohol and drugs or after an accident.

When accessing someone’s eligibility for the Disability Support Pension, for example, people with an intellectual disability often need to have an IQ (intelligence quotient) lower than 70. They may have difficulty looking after themselves, communicating and socialising without support.

While autism spectrum disorder is not an intellectual disability, some people with ASD may also have intellectual disability. Autism spectrum disorder is a lifelong developmental condition categorised by difficulties in social interaction, communication, sensory processing difficulties and restricted interests and behaviours. People with autism spectrum disorder relate to their environment and other people differently.

Intellectual disability can also occur with other conditions including:

Developmental delay – All children develop at different rates. However, when a child develops at a slower rate than other children of the same age and doesn’t reach milestones at the expected times, this is known as a developmental delay. These delays may occur in the way a child moves, communicates, thinks, learns or behaves with others. The right support can help a child to develop to their full potential. A child born with developmental delay does not always mean they will live with disability.

Down syndrome – Down syndrome is one of the most common genetic causes of intellectual disability. People living with Down syndrome have characteristic physical features and a delay in development. It is caused by the development of an extra chromosome 21 during pregnancy and affects approximately one in 700 – 900 babies.

Fetal alcohol spectrum disorder – A lifelong condition relating to permanent brain damage caused by fetal alcohol exposure. The majority of children and adults who have FASD experience significant cognitive, behaviour, health and learning difficulties, including problems with memory, attention, impulsive behaviours, problem-solving, cause-and-effect reasoning and adaptive functioning difficulties.

Fragile X syndrome – A genetic condition causing intellectual disability, behaviour difficulties such as anxiety, shyness, Attention Deficit Hyperactivity Disorder, and aggression; learning challenges, development delay, speech and communication difficulties and various physical characteristics. FXS is the most common single-gene cause of autism worldwide, with males generally affected with greater severity.

What other factors are there to life with intellectual disability?

Viral or bacterial infections during pregnancy, complications during birth or following an illness, such as measles or meningitis, malnutrition and exposure to alcohol, drugs or other toxins can also result in intellectual disability.

Children with intellectual disability are likely to be eligible for early intervention support through the National Disability Insurance Scheme.

Adults with intellectual disability may also be able to access NDIS funds for supports, such as services to help them live independently or access the community.

People with intellectual disability may also have a separate or related physical disability or a mental health condition.

Some people may not have a formal diagnosis of a condition that causes intellectual disability. This is why the social model of disability is used in Australia and not the medical model of disability.

The medical model of disability focuses on the diagnosis that a person has, whereas the social model of disability focuses on how their life is impacted by the way society treats them.

Under the social model, any person who is disabled by the barriers that society places in front of them, such as learning or communication methods that do not suit a person with an intellectual disability, should receive support to overcome those barriers.

What else would you like to know about intellectual disability?

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Related content:
What are the types of hidden disabilities
Am I eligible for the NDIS?
Early intervention under the NDIS