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Intellectual Disability

Children with intellectual disability have below average intelligence. A child who is intellectually disabled cannot easily change his behavior in response to certain situations or demands.

There are 4 levels of intellectual disability: mild, moderate, severe, and profound. These levels are measured using a standard test.

What is the cause?

The most common cause of intellectual disability during pregnancy is drug or alcohol use by the mother. Intellectual disability may also result if the mother:

  • has illnesses such as syphilis or German measles (rubella)
  • eats a poor diet
  • is exposed to toxic chemicals while she is pregnant

Loss of oxygen to the baby for a long time during birth, such as when the umbilical cord is wrapped around the neck, may cause brain damage which results in intellectual disability.

Over 500 genetic diseases may cause intellectual disability. Some examples of these diseases are:

  • Fragile X Syndrome
  • Down Syndrome
  • PKU (phenylketonuria)
  • Tay-Sachs Disease

Problems during childhood may lead to intellectual disability:

  • diseases such as whooping cough, measles, and certain kinds of bacteria
  • accidents such as a blow to the head or near drowning
  • exposure to lead, mercury, and chemical fertilizers
  • poor diet and neglect

If you suspect your child has intellectual disability, talk to your healthcare provider. Your provider may need to search for the cause. Some disorders require special medical care. A genetic problem may be discovered. If it is a genetic problem you may want to talk to your provider before you decide to have more children.

What kind of testing will my child have?

Newborns in the US are tested soon after birth, but different states test for different conditions. Some conditions, such as phenylketonuria (PKU), galactosemia, and congenital hypothyroidism, can cause intellectual disability and other problems if babies are not treated soon after birth.

Children who have these conditions can be treated with medicine or put on a special diet.

It is not always easy to figure out the degree of disability or predict how a child will develop over time. Standardized screening tools can help find children who are at risk. As your child grows, tests are used to measure how well your child is developing compared to other children of the same age. If your child's intellectual age is a lot lower than your child's actual age, then he or she probably has intellectual disability.

In the preschool and school-age years, your child can be given an IQ test. IQ stands for intelligence quotient. The IQ test can show the degree of intellectual disability. The test helps predict how well your child will do academically and socially. Your healthcare provider or other specialists will figure out which tests are best for your child.

How will my child develop?

Most children with intellectual disability will learn new things but at a slower pace than normal. Your child's ability to function mentally, physically, and behaviorally depends on the severity of the intellectual disability.

Mild (IQ range 55 to 69). Preschool-age children with mild intellectual disability often do not seem very different than other children. However, they are slower than most children to walk, feed themselves, and talk. Children with mild intellectual disability can learn practical skills and reading and math to a 3rd- to 6th-grade level. As adults, they can usually hold simple jobs and live by themselves. However, they may need some guidance and support during times of unusual stress.

Moderate (IQ range 40 to 54). Preschool-age children with moderate intellectual disability show noticeable delays in development of motor skills and speech. Older children can learn simple communication, health and safety habits, and self-help skills. Most cannot learn basic reading and writing skills beyond simple words. As adults, they can do simple tasks under supervision and can travel alone in familiar places. They usually cannot live completely by themselves.

Severe (IQ range 25 to 39). Preschool-age children with severe intellectual disability have delays in motor development and little or no communication skills. With training, these children may be able to learn basic self-help skills, such as feeding themselves and bathing. As they grow older they can usually walk. They may understand some speech and be able to make some response. As adults, they can get used to routines, but will need direction and supervision.

Profound (IQ less than 24). Children with profound intellectual disability often have other medical problems, such as cerebral palsy. They may need nursing care. They have delays in all areas of development. They show basic emotions and with training, may be able to use their legs, hands, and jaws. Most need to be supervised closely during all waking hours.

Most people with intellectual disability will only be a little slower than average in learning new information and skills. Mild intellectual disability may not be recognized until a child starts school. Most people with mild intellectual disability can learn reading, writing, and math skills up to the 3rd to 6th grade level. With some help, most can successfully live by themselves and hold simple jobs.

How is intellectual disability treated?

Treatment focuses on educational, behavioral, and self-help skills.

Most states offer Early Intervention Programs (EIP) for children aged 0 to 3 years with intellectual disability. Some states also offer special classes to children between the ages of 3 and 5 years who have special needs. By law, all states must provide special education classes for children with intellectual disability through 21 years of age.

The school must develop an Individual Educational Plan (IEP) for each child who needs special education. This plan includes:

  • educational objectives
  • class placement
  • a plan to check progress
  • any other special services, such as therapy or transportation.

Both the parent and the school must agree to the plan.

Parents of children with intellectual disability often hear of new and different treatments through the media or friends. Your provider can help you decide if these treatments could help or harm your child.

Where can my family get help and support?

When parents hear for the first time that their child is intellectually disabled, they can feel grief, anger, guilt, and many other emotions. Many families find that counseling can help. A child's disability affects the entire family, including brothers and sisters. You can learn what help is available through the national and local chapters of The ARC.

Telephone: 1-800-433-5255
Web site:

Written by the Section of Developmental-Behavioral Pediatrics, Hackensack Medical Center's Institute for Child Development in Hackensack, New Jersey.
Published by RelayHealth.
Last modified: 2010-08-26
Last reviewed: 2010-03-02

This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a health care professional.

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