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Frequently Asked Questions About Intellectual & Developmental Disability

What is an Intellectual/Developmental Disability

An individual is considered to have an intellectual disability based on three criteria:

  1. What is Intellectual Disability?

    • Intellectual functioning level (IQ) below 70-75

    • Significant limitations  in two or more adaptive skill areas

    • Condition present from childhood (defined as age 18 or less)

How many individuals are affected by Intellectual Disability

Various studies have been conducted in local communities to determine the prevalence of people with intellectual disability. The Arc reviewed many of these prevalence studies in the early 1980s and concluded that 2.5 to 3 percent of the general population has intellectual disability (The Arc, 1982.) A 1993 review of prevalence studies generally confirms this distribution (Fryers, 1993.)

Based on the 1990 census, an estimated 6.2 to 7.5 million people have intellectual disability. Intellectual Disability is 12 times more common than cerebral palsy and 30 times more prevalent than neural tube defects such as spina bifida. It affects 100 times as many people as total blindness (Batshaw & Perret, 1992).

Intellectual disability cuts across the lines of racial, ethnic, educational, social and economic background. It can occur in any family. One in ten American families is directly affected by intellectual disability.

How does intellectual disability affect individuals?

The effects of intellectual disability vary considerably among people, just as the range of abilities varies considerably among people who do not have this disability. About 87 percent of individuals will be mildly affected and will be only a little slower than average in learning new information and skills. As children,  disability is not readily apparent and may not be identified until school age.  As adults, many people will be able to lead independent lives in the community and will no longer be viewed as having an intellectual disability.

The remaining 13 percent of people with intellectual disability, those with IQs under 50, may have serious limitations in functioning.  However, with early intervention, a functional education and appropriate supports as an adult, all individuals can lead satisfying lives in the community.

AAIDD’s definition no longer labels individuals according to the categories of mild, moderate, severe and profound intellectual disability based on IQ level.  Instead, it looks at the intensity and pattern of changing supports needed by an individual over a lifetime.

What is people-first language & why is important?

People with disabilities are – first and foremost – people who have individual abilities, interests and needs.  Approximately 54 million Americans -- one out of every five individuals -- have a disability.

The language a society uses to refer to persons with disabilities shapes its beliefs and ideas about them. Words are powerful; Old, inaccurate, and inappropriate descriptors perpetuate negative stereotypes and attitudinal barriers. When we describe people by their labels of medical diagnoses, we devalue and disrespect them as individuals.

In contrast, using thoughtful terminology can foster positive attitudes about persons with disabilities. One of the major improvements in communicating with and about people with disabilities is "People-First Language.”

People-First Language emphasizes the person, not the disability. By placing the person first, the disability is no longer the primary, defining characteristic of an individual, but one of several aspects of the whole person. People-First Language is an objective way of acknowledging, communicating, and reporting on disabilities. It eliminates generalizations and stereotypes, by focusing on the person rather than the disability.

Disability is not the “problem.” For example, a person who wears glasses doesn’t say, “I have a problem seeing,” they say, “I wear/need glasses.” Similarly, a person who uses a wheelchair doesn’t say, “I have a problem walking,” they say, “I use/need a wheelchair.”

Our words and the meanings we attach to them create attitudes, drive social policies and laws, influence our feelings and decisions, and affect people’s daily lives and more. How we use them makes a difference. People First Language puts the person before the disability, and describes what a person has, not who a person is. Using a diagnosis as a defining characteristic reflects prejudice, and also robs the person of the opportunity to define him/herself.

-This has been adaptive from The Arc Us



The Arc of United States


The Arc Of Connecticut


CT Department of Developmental Services

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