Intellectual Disability

Intellectual disability is usually identified during childhood, and has an ongoing impact on a child’s development.

With varying degrees of severity, intellectual disability can involve difficulties with communication, memory, understanding, problem solving, fine and gross motor skills, and self-care.

It is diagnosed through formal testing, including an IQ test. Children with mild intellectual disability (IQ between 55-69) may not be detected until after starting school.

Early signs of possible intellectual disability include developmental delays and behavioural and social problems. Causes include genetic conditions, problems during pregnancy or at birth, infections and environmental factors. Some causes are listed below.

Down syndrome

Down syndrome is the most common biological cause of intellectual disability. It occurs when there is an extra copy of chromosome 21 and leads to distinct physical characteristics. Diagnosis is usually before or just after birth. In Western Australia, about one in 900 children are born with Down syndrome each year.

Fragile X syndrome

Fragile X syndrome is the most common cause of inherited intellectual disability. It is caused by a change in the fragile X mental retardation 1 gene and affects about 1 in 4000 boys and 1 in 6000 girls. It results in intellectual disability, and behavioural and learning challenges.

Rett syndrome

Rett syndrome is a neurological disorder caused by mutations in the MECP2 gene which interferes with body movement. It affects about one in every 9000 girls. Development may be normal during infancy.

CDKL5 disorder

Once considered an atypical form of Rett syndrome, CDKL5 disorder results in seizures and severe neuro-developmental impairment. Most cannot walk, talk or feed themselves.

*If you are concerned about your child’s development, you should seek advice from a professional. Getting assessed will provide access to early intervention, education and support.