Intellectual disability (used to be Cognitive Disability) is a term used when a person has certain limitations in mental functioning and in skills such as communicating, taking care of themselves-, and social skills. These limitations will cause a child to learn and develop more slowly than a typical child. Children with intellectual disabilities may take longer to learn to speak, walk, and take care of their personal needs such as dressing or eating. They are likely to have trouble learning in school. They will learn, but it will take them longer. There may be some things they cannot learn.
What Causes Intellectual Disability?
Doctors have found many causes of intellectual disabilities. The most common are:
- Genetic conditions. Sometimes an intellectual disability is caused by abnormal genes inherited from parents, errors when genes combine, or other reasons. Examples of genetic conditions are Down syndrome, fragile X syndrome, and phenylketonuria (PKU).
- Problems during pregnancy. Intellectual disabilities can result when the baby does not develop inside the mother properly. For example, there may be a problem with the way the baby's cells divide as it grows. A woman who drinks alcohol or gets an infection like rubella during pregnancy may also have a baby with intellectual disabilities.
- Problems at birth. If a baby has problems during labor and birth, such as not getting enough oxygen, they may have an intellectual disability.
- Health problems. Diseases like whooping cough, the measles, or meningitis can cause intellectual disabilities. This can also be caused by extreme malnutrition (not eating right), not getting enough medical care, or by being exposed to poisons like lead or mercury.
An intellectual disability is not a disease. You can't catch an intellectual disability from anyone. It is also not a type of mental illness, like depression. There is no cure for an intellectual disability. However, most children with this disability can learn to do many things. It just takes them more time and effort than other children.
How is an Intellectual Disability Diagnosed?
Intellectual Disabilities are diagnosed by looking at two main things. These are:
- the ability of a person's brain to learn, think, solve problems, and make sense of the world (called IQ or intellectual functioning); and
- whether the person has the skills they need to live independently (called adaptive behavior, or adaptive functioning).
Intellectual functioning, or IQ, is usually measured by a test called an IQ test. The average score is 100. People scoring below 70 to 75 are thought to have an intellectual disability. To measure adaptive behavior, professionals look at what a child can do in comparison to other children of their age. Certain skills are important to adaptive behavior. These are:
- daily living skills, such as getting dressed, going to the bathroom, and feeding one's self;
- communication skills, such as understanding what is said and being able to answer;
- social skills with peers, family members, adults, and others.
To diagnose an intellectual disability, professionals look at the person's mental abilities (IQ) and their adaptive skills. Both of these are highlighted in the definition of intellectual disability provided between the lines below. This definition comes from the Individuals with Disabilities Education Act (IDEA). The IDEA is the federal law that guides how schools provide early intervention and special education and related services to children with disabilities.
Providing services to help individuals with intellectual disabilities has led to a new understanding of how we define this disability. After the initial diagnosis is made, we look at a person's strengths and weaknesses. We also look at how much support or help the person needs to get along at home, in school, and in the community. This approach gives a realistic picture of each individual. It also recognizes that the "picture" can change. As the person grows and learns, their ability to get along in the world grows as well.
IDEA's Definition of "Intellectual Disability"
Our nation's special education law, the IDEA, defines a intellectual disability as "significantly subaverage general intellectual functioning, existing concurrently with deficits in adaptive behavior and manifested during the developmental period, that adversely affects a child's educational performance." [34 Code of Federal Regulations §300.7(c)(6)]
How Common is an Intellectual Disability?
As many as 3 out of every 100 people in the country have an intellectual disability (The Arc, 2001). Nearly 613,000 children ages 6 to 21 have some level of a intellectual disability and need special education in school (Twenty-fourth Annual Report to Congress, U.S. Department of Education, 2002). In fact, 1 out of every 10 children who need special education has some form of intellectual disability.
What Are the Signs of Intellectual Disability)?
There are many signs of intellectual disability. For example, children with this disability may:
- sit up, crawl, or walk later than other children;
- learn to talk later, or have trouble speaking,
- find it hard to remember things,
- not understand how to pay for things,
- have trouble understanding social rules,
- have trouble seeing the consequences of their actions,
- have trouble solving problems, and/or
- have trouble thinking logically.
About 87% of people with intellectual disabilities will only be a little slower than average in learning new information and skills. When they are children, their limitations may not be obvious. They may not even be diagnosed as having an intellectual disability until they get to school. As they become adults, many people with this disability can live independently. Other people may not even consider them as having a disability. The remaining 13% of people with an intellectual disability score below 50 on IQ tests. These people will have more difficulty in school, at home, and in the community. A person with more severe intellectual disability will need more intensive support their entire life. Every child with this disability is able to learn, develop, and grow. With help, all children with an intellectual disability can live a satisfying life.