Causes of intellectual disability and health care

Key facts

Families and disability workers usually want to know what causes an intellectual disability. Knowing the cause can help professionals advise how the person will develop and how to meet the person’s needs.

Intellectual disability is not a disease or mental illness. But some causes of intellectual disability can make a person more likely to get particular health conditions.

In many cases, doctors cannot identify what causes an intellectual disability. In other cases they can work out the cause. There are many causes, including:

• genetic conditions

• problems during pregnancy

• problems at birth

• health problems in childhood

Paediatricians may be able to tell you the cause of an intellectual disability. In some cases, the paediatrician will refer you to a specialist diagnosis and assessment service.

Genetic conditions

One of the most common causes of intellectual disability is abnormal genes. Sometimes, these are inherited from parents. Examples of genetic conditions are syndromes like Down syndrome, fragile X syndrome and Prader-Willi syndrome.

Problems during pregnancy

There can be problems with the way the cells divide as a baby grows. A woman who drinks alcohol or takes drugs may also have a baby with intellectual disability. If a woman gets an infection like rubella (German measles) during pregnancy, then the baby may have intellectual disability.

Problems at birth

If a baby does not get enough oxygen during labour or birth, they may have intellectual disability. Also babies who are born very premature may have intellectual disability.

Health problems during childhood

Diseases like whooping cough, the measles, or meningitis can cause an intellectual disability. Intellectual disability can also be caused by extreme malnutrition, not getting good medical care, or being exposed to poisons like lead or mercury.

Some syndromes and health conditions

Overall, people with intellectual disability are more likely to have problems with hearing, vision, teeth, epilepsy, heart disease and thyroid function.

People with a specific syndrome may be more likely to get a particular disease or condition than other people. Here are some examples:

• People with Down syndrome may be born with heart defects.

• People with Prader-Will syndrome may have Type 2 diabetes or delayed puberty.

• People with fragile X syndrome may have ADHD - attention deficit hyperactivity disorder.

• People with Angelmann syndrome may have severe epilepsy.

• Women with Rett Syndrome may break their bones more easily because they can have low bone density.

Some GPs may not be aware of the health conditions that affect people with specific syndromes. And so, it is important to get advice from a paediatrician or another doctor who has specialised knowledge about intellectual disability.

For more information

Down syndrome and health fact sheet, Better Health Channel
www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Down_syndrome_and_health?OpenDocument

Fact sheets on syndromes, Centre for Developmental Disability Health
www.cddh.monash.org/products-resources.html#factsheets

In Health Care for People with Intellectual Disabilities – Guidelines for general practitioners, there is a list of health conditions that can occur with different syndromes, and contact information for associations on syndromes, eg Down Syndrome Association
www.cds.med.usyd.edu.au/cdsresearch/publications-and-presentations/cat_view/50-health-publications

You might be interested in this fact sheet

Diagnosis and assessment of a disability

This fact sheet was updated in May 2011.

The fact sheet contains general information only and does not take into account individual circumstances. It should not be relied on for medical advice. We encourage you to look at the information in this fact sheet carefully with your health professional to decide whether the information is right for you.