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Intellectual Disability

Intellectual disability is a birth defect that affects the brain and development.

What It Is

Children born with intellectual disability have mental limitations that lessen their ability to communicate, interact socially and function independently. Children with intellectual disability will lag behind other children in their age group, taking longer to learn to walk, speak and take care of themselves.

Intellectual disability is diagnosed by looking at two different aspects of a person’s ability:

  • Intellectual functioning, which takes into account an individual’s ability to learn, think, solve problems and comprehend the surrounding world. Intellectual functioning is usually measured with an I.Q. test. While the average I.Q. is 100, those scoring below the 70-75 range meet the diagnosis of having an intellectual disability.
  • Adaptive functioning, which measures whether an individual has the skills necessary to live independently. Typically, this is assessed by observing what a child can do in comparison to his or her peers in the following areas:
    • Daily living skills (using the bathroom, dressing oneself, eating a meal)
    • Communication skills (understanding and responding appropriately to another person)
    • Social skills (interactions with peers, adults and family members)

In cases of severe intellectual disability, a diagnosis may be made soon after birth. For more mild cases, the disability may not be diagnosable until later in life when the child attends school. Symptoms and abilities may vary greatly, but most children will need additional supervision and support, particularly in childhood and in school settings.

Intellectual disability is the most common developmental disability, affecting about 1-3% of the population. Accordingly, many support networks and educational programs exist to offer assistance to the approximately 6.5 million Americans who are living with intellectual disability.


Symptoms for children with intellectual disabilities vary greatly, but may include:

  • Delayed motor skills- child learns to sit up, crawl or walk later than other children
  • Delayed language skills- child learns to talk later and may struggle with speech
  • Decreased ability to learn
  • Difficulty solving problems and/or thinking logically
  • Difficulty understanding social rules
  • Difficulty understanding consequences of their actions
  • In more severe cases, infant-like behavior throughout life


Depakote: A recent study found a link between first trimester use of the anti-epilepsy drug Depakote and increased risk of delivering a baby with intellectual disability. Researchers found that toddlers who had been exposed to Depakote in the womb were twice as likely to suffer from I.Q. levels associated with intellectual disability.


Mental deficiency cannot be cured, but treatment is important in developing the individual to the best of his or her potential. Early intervention involves a nationwide system of services designed to support infants and toddlers with disabilities. Staff members work with families to develop tailored plans that can support the child’s intellectual development. Services are available on a sliding scale in most communities across the country. When a child with mental deficiency reaches school age, he or she is protected by a law that guarantees the availability of free special education designed to meet his or her needs.


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