Intellectual Disability

Intellectual disability (ID), once called mental retardation, is characterized by below-average intelligence or mental ability and a lack of skills necessary for day-to-day living. People with intellectual disabilities can and do learn new skills, but they learn them more slowly. There are varying degrees of intellectual disability, from mild to profound.

What is intellectual disability?

Someone with intellectual disability has limitations in two areas. These areas are:

  • Intellectual functioning. Also known as IQ, this refers to a person’s ability to learn, reason, make decisions, and solve problems.
  • Adaptive behaviors. These are skills necessary for day-to-day life, such as being able to communicate effectively, interact with others, and take care of oneself.

IQ (intelligence quotient) is measured by an IQ test. The average IQ is 100, with the majority of people scoring between 85 and 115. A person is considered intellectually disabled if he or she has an IQ of less than 70 to 75.

To measure a child’s adaptive behaviors, a specialist will observe the child’s skills and compare them to other children of the same age. Things that may be observed include how well the child can feed or dress himself or herself; how well the child is able to communicate with and understand others; and how the child interacts with family, friends, and other children of the same age.

Intellectual disability is thought to affect about 1% of the population. Of those affected, 85% have mild intellectual disability. This means they are just a little slower than average to learn new information or skills. With the right support, most will be able to live independently as adults.

What are the signs of intellectual disability in children?

There are many different signs of intellectual disability in children. Signs may appear during infancy, or they may not be noticeable until a child reaches school age. It often depends on the severity of the disability. Some of the most common signs of intellectual disability are:

  • Rolling over, sitting up, crawling, or walking late
  • Talking late or having trouble with talking
  • Slow to master things like potty training, dressing, and feeding himself or herself
  • Difficulty remembering things
  • Inability to connect actions with consequences
  • Behavior problems such as explosive tantrums
  • Difficulty with problem-solving or logical thinking

In children with severe or profound intellectual disability, there may be other health problems as well. These problems may include seizures, mood disorders (anxiety, autism, etc.), motor skills impairment, vision problems, or hearing problems.


What causes intellectual disability?

Anytime something interferes with normal brain development, intellectual disability can result. However, a specific cause for intellectual disability can only be pinpointed about a third of the time.

The most common causes of intellectual disability are:

  • Genetic conditions. These include things like Down syndrome and fragile X syndrome.
  • Problems during pregnancy. Things that can interfere with fetal brain development include alcohol or drug use, malnutrition, certain infections, or preeclampsia.
  • Problems during childbirth. Intellectual disability may result if a baby is deprived of oxygen during childbirth or born extremely premature.
  • Illness or injury. Infections like meningitis, whooping cough, or the measles can lead to intellectual disability. Severe head injury, near-drowning, extreme malnutrition, infections in the brain, exposure to toxic substances such as lead, and severe neglect or abuse can also cause it.
  • None of the above. In two-thirds of all children who have intellectual disability, the cause is unknown.


Can intellectual disability be prevented?

Certain causes of intellectual disability are preventable. The most common of these is fetal alcohol syndrome. Pregnant women shouldn’t drink alcohol. Getting proper prenatal care, taking a prenatal vitamin, and getting vaccinated against certain infectious diseases can also lower the risk that your child will be born with intellectual disabilities.

In families with a history of genetic disorders, genetic testing may be recommended before conception.

Certain tests, such as ultrasound and amniocentesis, can also be performed during pregnancy to look for problems associated with intellectual disability. Although these tests may identify problems before birth, they cannot correct them.

How is intellectual disability diagnosed?

Intellectual disability may be suspected for many different reasons. If a baby has physical abnormalities that suggest a genetic or metabolic disorder, a variety of tests may be done to confirm the diagnosis. These include blood tests, urine tests, imaging tests to look for structural problems in the brain, or electroencephalogram (EEG) to look for evidence of seizures.

In children with developmental delays, the doctor will perform tests to rule out other problems, including hearing problems and certain neurological disorders. If no other cause can be found for the delays, the child will be referred for formal testing.


Three things factor into the diagnosis of intellectual disability: interviews with the parents, observation of the child, and testing of intelligence and adaptive behaviors. A child is considered intellectually disabled if he or she has deficits in both IQ and adaptive behaviors. If only one or the other is present, the child is not considered intellectually disabled.

After a diagnosis of intellectual disability is made, a team of professionals will assess the child’s particular strengths and weaknesses. This helps them determine how much and what kind of support the child will need to succeed at home, in school, and in the community.

What services are available for people with intellectual disability?

For babies and toddlers, early intervention programs are available. A team of professionals works with parents to write an Individualized Family Service Plan, or IFSP. This document outlines the child’s specific needs and what services will help the child thrive. Early intervention may include speech therapy, occupational therapy, physical therapy, family counseling, training with special assistive devices, or nutrition services.

School-age children with intellectual disabilities (including preschoolers) are eligible for special education for free through the public school system. This is mandated by the Individuals With Disabilities Education Act (IDEA). Parents and educators work together to create an Individualized Education Program, or IEP, which outlines the child’s needs and the services the child will receive at school. The point of special education is to make adaptations, accommodations, and modifications that allow a child with an intellectual disability to succeed in the classroom.

What can I do to help my intellectually disabled child?

Steps to help your intellectually disabled child include:

  • Learn everything you can about intellectual disabilities. The more you know, the better advocate you can be for your child.
  • Encourage your child’s independence. Let your child try new things and encourage your child to do things by himself or herself. Provide guidance when it’s needed and give positive feedback when your child does something well or masters something new.
  • Get your child involved in group activities. Taking an art class or participating in Scouts will help your child build social skills.
  • Stay involved. By keeping in touch with your child’s teachers, you’ll be able to follow his or her progress and reinforce what your child is learning at school through practice at home.
  • Get to know other parents of intellectually disabled children. They can be a great source of advice and emotional support.
WebMD Medical Reference Reviewed by Smitha Bhandari, MD on May 31, 2016



CDC: “Intellectual Disability.”

UpToDate: “Intellectual disability (mental retardation) in children: Definition; causes; and diagnosis.”

American Association on Intellectual and Developmental Disabilities.

National Dissemination Center for Children With Disabilities: “Intellectual Disability (formerly Mental Retardation),” “Overview of Early Intervention,” “Supports, Modifications and Accommodations for Students,” and “10 Basic Steps in Special Education.”

Merck Manual: “Mental Retardation/Intellectual Disability.”

© 2016 WebMD, LLC. All rights reserved.


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