17.2.1  What causes intellectual disability?

The primary cause of ID appears to be problems with the development of the brain. In most children with ID we do not know precisely why the children have ID. But some of the factors that we know about include:

• Problems before the child is born: poor nutrition or excessive alcohol consumption by the mother during pregnancy, exposure to certain types of infections prenatally.
• Problems during childbirth: prolonged labour.
• Problems in the first year of life: infections of the brain; accidents or severe malnutrition.
• Some genetic conditions, for example Down syndrome.

Down syndrome is the commonest identifiable cause of ID in Europe. A child with Down syndrome is usually of short stature and has physical characteristics (including an unusually round face, a protruding or oversized tongue and unusually shaped eyes) that make them look different from other children. The mother’s age is the commonest risk factor in relation to Down syndrome: at age 28, the risk is about 1 in 800 live births, at the age of 38, the risk increases to about 1 in 200; and by the age of 48, this rises dramatically to about 1 in 10 live births. Given this, one of the things you can do in your community is to encourage women to try and avoid pregnancy after the age of 40.

Other risk factors that may affect the intellectual development of a child include problems in the way the child is being looked after, such as poor stimulation, child abuse and emotional neglect.