Intellectual Disability

What is an intellectual disability?

People with an intellectual disability (ID) have intelligence that is below the normal range, which means they are slower at learning to walk, feed themselves, or talk. They may not be able to read, write, solve problems, or do math past the 3rd to 6th grade level, if at all. People with ID may also be called developmentally disabled.

ID causes trouble with things like:

  • Being able to communicate and understand others, such as talking, writing, or following directions
  • Taking care of themselves or being able to live alone
  • Homemaking, such as cooking and cleaning
  • Social skills such as the give-and-take of dealing with people and controlling emotions
  • Being able to get and keep a job

What is the cause?

Many problems can cause ID. In about one third of the people with ID the cause is unknown. Intellectual disability is more common in males than in females.

Genetic problems are passed from parents to children through their genes. Genes are inside each cell of the body. They contain the information that tells the body how to develop and work. Over 500 genetic diseases have been linked to ID, such as:

  • Fragile X Syndrome, which keeps the body from making a certain protein
  • Down Syndrome, which causes problems with how the brain and body develop
  • PKU (phenylketonuria), which keeps the body from breaking down an amino acid (a building block for protein)

ID may be caused during pregnancy if the mother:

  • Uses drugs or drinks alcohol
  • Has illnesses such as syphilis or German measles (rubella)
  • Is exposed to toxic chemicals

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 that results in ID.

Problems during childhood may lead to ID:

  • Diseases such as whooping cough, measles, and meningitis
  • A serious head injury or near drowning
  • Contact with lead, mercury, and some chemical fertilizers
  • Poor diet and neglect over a long time

What are the symptoms?

Symptoms usually start before age 18. Symptoms depend on how severe the intellectual disability is.

Most people with ID have a mild form. People with mild ID can learn reading, writing, and math skills up to the 3rd to 6th grade level. With some help, most can live by themselves and hold simple jobs.

People with a more severe ID can learn some basic skills such as bathing and feeding themselves. They have very limited ability to communicate with others. Many can learn to do simple tasks with close supervision.

People with the most severe kind of intellectual disability often have other medical problems, such as trouble swallowing or moving. They show basic emotions and with therapy, may be able to use their legs, hands, and mouth. Many need nursing care. Most need to be supervised closely during all waking hours.

How is it diagnosed?

ID is almost always diagnosed in childhood. Mild ID may not be diagnosed until a child starts school.

Both intelligence and life skills should be tested every few years to check the progress made from education and therapy. A psychologist or developmental specialist does the testing. Tests may include:

  • Thinking and general knowledge
  • Word use and communication
  • Making and copying symbols or pictures
  • Putting puzzles together
  • Self-care skills such as being able to shop, cook, and get dressed
  • Social skills

How is it treated?

Treatment focuses on educational, behavioral, and self-help skills. Many programs can help people with ID to learn better skills. People with ID are slower to learn than most people, but they can increase their skills.

Where can I get help?

When someone in the family has an intellectual disability, everyone in the family can feel grief, anger, guilt, and many other emotions. Many families find that counseling can help.

You can get help and training from many government agencies and private programs. All states have special programs for people with ID. The programs for adults usually start after age 21 when schools no longer provide services. Job training and coaching programs are available through each state’s Division of Vocational Rehabilitation. Private organizations like Goodwill and The ARC also offer services in many locations.

Community resources are very important. To find these services, talk with your healthcare provider or county health department:

  • Social workers find and organize help, including possible financial aid.
  • Home healthcare agencies provide the services of nurses, medical social workers, and therapists. They also provide home health aides for personal care.
  • Out-of-home services include mental health services, transportation, and nursing facilities.

Get immediate help if someone with ID becomes violent or starts to harm himself or herself. Sometimes people with ID bang their heads or other body parts against things. You will need to help them move to a safe place or remove items around them so they don’t hurt themselves.

You can learn more from:

Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth.
Last modified: 2014-11-04
Last reviewed: 2014-12-31
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 healthcare professional.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.

Patient Portal

myTuftsMed is our new online patient portal that provides you with access to your medical information in one place. MyTuftsMed can be accessed online or from your mobile device providing a convenient way to manage your health care needs from wherever you are.

With myTuftsMed, you can:

  1. View your health information including your medications, test results, scheduled appointments, medical bills even if you have multiple doctors in different locations.
  2. Make appointments at your convenience, complete pre-visit forms and medical questionnaires and find care or an emergency room.
  3. Connect with a doctor no matter where you are.
  4. Keep track of your children’s and family members’ medical care, view upcoming appointments, book visits and review test results.
  5. Check in on family members who need extra help, all from your private account.


Your privacy is important to us. Learn more about ourwebsite privacy policy. X