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Home > A-Z Health Topics > Illnesses and Disabilities > Types of illnesses and disabilities > Intellectual disability

Intellectual disability

• More information on intellectual disability

Intellectual disability (formerly called mental retardation) is a term used when you are limited in your ability to:

• Learn, think, solve problems, and make sense of the world (called intellectual functioning)
• Live independently (called adaptive behavior)

Intellectual functioning is usually measured with an IQ test. The average score is 100. If you score below 70 or 75, you are said to have an intellectual disability. Adaptive behavior is measured by looking at:

• Daily living skills, such as getting dressed, going to the bathroom, and feeding yourself
• Understanding what is said and being able to answer
• Social skills with peers, family members, adults, and others

Doctors have found many causes of intellectual disability. But the reason is not known about 40 percent to 50 percent of the time. Some causes are:

• Genetic disorders, such as Down syndrome ("genetic" means that it runs in families)
• Fetal alcohol spectrum disorders
• Problems during pregnancy or childbirth
• Childhood diseases like whooping cough or measles
• Poor nutrition (not eating well)
• Being exposed to poisons like lead or mercury

There is no cure for intellectual disability. But most people with intellectual disability can learn to do many things. With support, adults with mild intellectual disabilities often can live and work on their own.

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More information on intellectual disability

Explore other publications and websites

• Developmental Disabilities — This page provides links to information from the Centers for Disease Control and Prevention on different developmental disabilities, including autism spectrum disorders, cerebral palsy, and mental retardation.
  http://www.cdc.gov/ncbddd/dd/
• Intellectual Disability (Copyright © National Dissemination Center for Children with Disabilities) — This fact sheet provides basic background information on mental retardation, what causes it, and how it's diagnosed. Also, it gives useful tips to parents and teachers about dealing with mental retardation and how to provide a better environment for the child.
  http://www.nichcy.org/Disabilities/Specific/Pages/IntellectualDisability.aspx
• Mental Retardation — This publication discusses why the main causes of mental retardation 30 years ago are no longer causes today. It also discusses research efforts to further reduce the number of children born with mental retardation or reduce the effects of mental retardation.
  http://health.nih.gov/topic/DevelopmentalDisabilities/MentalHealthandBehavior

Connect with other organizations

• American Association on Intellectual and Developmental Disabilities
  http://www.aamr.org
• American Network of Community Options and Resources
  http://www.ancor.org/
• Association of University Centers on Disabilities
  http://www.aucd.org/template/index.cfm
• Devereux Foundation
  http://www.devereux.org/site/PageServer
• March of Dimes
  http://www.marchofdimes.com
• President's Committee for People With Intellectual Disabilities, ACF, HHS
  http://www.acf.hhs.gov/programs/pcpid/
• Public Information and Communications Branch, NICHD, NIH, HHS
  http://www.nichd.nih.gov
• The Arc
  http://www.thearc.org
• The Feingold Center for Children
  http://www.thefeingoldcenter.org/index.htm

Content last updated September 22, 2009.

Resources last updated September 22, 2009.

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