Intellectual disabilities or impairments develop before adulthood and can affect a person’s ability to learn, communicate, retain information, and undertake work or leisure activities. An intellectual disability may be caused by genetic conditions, problems during pregnancy and birth, illness, or environmental factors.

Categories of mild, moderate, severe and profound levels of intellectual impairment are defined on the basis of IQ scores. A person is classified as having an intellectual disability if their IQ falls below 70.

Achieve Australia supports people with various intellectual disabilities to lead valued and meaningful lives, some of which are defined below.

What is intellectual disability?


Autism is a severe behaviour disorder which developed in early childhood and affects the way an individual interacts with their environment and other people. It is a neurological disorder characterised by social and cognitive difficulties and repetitive or restricted behaviours.

Fragile X syndrome (FXS)

Fragile X is a genetic condition caused by a mutation in the X chromosome. It results in intellectual impairment, behavioural and learning challenges and certain physical characteristics.

Down syndrome

Down Syndrome is a genetic disorder resulting from a full or partial extra copy of chromosome 21 in their DNA. This affects cognitive ability, can lead to a higher than normal incidence of respiratory and heart conditions, and leads to certain physical attributes. Down Syndrome is the most common chromosomal disorder and cause of learning disabilities in children (Mayo Clinic).

Developmental delay

Developmental delay is when a child falls behind the developmental milestones of other children of a similar age. These delays may occur in physical, learning, thinking, social and communicative development.

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