Definition

Intellectual disability is when a person has limits in:

• Intellectual function—learning, reasoning, and problem solving
• Adaptive behavior—daily tasks, such as communication and taking care of daily needs

Causes

The cause is not always known. The most common ones are:

• Genetic problems, such as Down syndrome and Fragile X syndrome
• Metabolic problems, such as phenylketonuria (PKU) and congenital hypothyroidism
• Problems with brain development, such as hydrocephalus and malformation
• Infections during pregnancy, such as toxoplasmosis, HIV, and rubella
• Unhealthy habits during pregnancy, such as substance and alcohol use disorder
• Problems at birth, such as being born very early or not getting enough oxygen
• Problems during childhood, such as:
  • Illnesses or infections that harm the brain, such as meningitis, encephalitis, and measles
  • Head injury or near drowning
  • Exposure to lead, mercury, and other toxins

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Risk Factors

This problem is more common in people who have other family members who have it. The risk is also higher in people who have any of the known causes.

Symptoms

Symptoms start before a child reaches age 18. Problems may be mild to severe. It varies from person to person.

Problems may be:

• Learning and developing more slowly than other children of the same age
• Problems communicating or socializing with others
• Trouble learning in school
• Problems doing everyday things like getting dressed or using the bathroom without help
• Problems hearing, seeing, walking, or talking
• Problems making decisions

Diagnosis

The doctor will ask about your child’s symptoms and health history. A physical exam will be done. Tests will be given to measure intellectual function and adaptive behavior.

Children with this problem have a higher risk for other disabilities. More tests may be done to look for these problems.

Treatment

There is no cure. The goal of treatment is to improve function and quality of life. This may allow some people to work and live on their own. Others may need support throughout their lives.

Treatment should be started early. Choices are:

• Speech, physical, and occupational therapy
• School-based services to help the child succeed in class
• Job skills training

Prevention

Proper prenatal care may lower the risk of some causes.