Definitions of Disability

The Web is filled with references to handicapped people and disabled people and people with disabilities.  But what is a disability?

Iezzoni and Freedman (2008) describe a "medical model of disability" (p. 332) originating in the 19th century. That model, they say, treats disability as a form of illness; and illnesses, in the medical model, are typically diagnosed in individuals and treated by doctors.  Against this, Iezzoni and Freedman contrast the "social model" (p. 333), which considers disability a social phenomenon.  In the words of the Fundamental Principles of Disability (1975) produced by the now apparently defunct Union of the Physical Impaired Against Segregation, "Disability is something imposed on top of our impairments, by the way we are unnecessarily isolated and excluded from full participation in society" (p. 3, cited by Oliver (1996, p. 22)).  In other words, there are a great many physical and mental impairments - the need to wear eyeglasses is an example - but not all impairments are treated equally; some result in much more isolation or stigma than others.

Within the social model of disability, Iezzoni and Freedman (2008) favor the definitional approach adopted by the World Health Organization's (WHO, 2009) International Classification of Functioning, Disability and Health (ICF):

The ICF puts the notions of ‘health’ and ‘disability’ in a new light. It acknowledges that every human being can experience a decrement in health and thereby experience some degree of disability. Disability is not something that only happens to a minority of humanity. The ICF thus ‘mainstreams’ the experience of disability and recognises it as a universal human experience. By shifting the focus from cause to impact it places all health conditions on an equal footing allowing them to be compared using a common metric – the ruler of health and disability. Furthermore ICF takes into account the social aspects of disability and does not see disability only as a 'medical' or 'biological' dysfunction. By including Contextual Factors, in which environmental factors are listed ICF allows to records the impact of the environment on the person's functioning.  [I have notified the webmaster of incoherence in that last sentence.]

Iezzoni and Freedman (2008) note, however, that different definitions serve different purposes, and that at present there are numerous legal definitions in use in the United States.  Two of the most prominent definitions they cite are those of the Americans with Disabilities Act of 1990 (ADA) and the Social Security Administration (SSA).  Section 12102(1) of the ADA defines disability as meaning, with respect to an individual, "(A) a physical or mental impairment that substantially limits one or more major life activities of such individual; (B) a record of such an impairment; or (C) being regarded as having such an impairment."  By contrast, the Social Security Advisory Board (2003) says that the Social Security Act of 1956 defined disability as “inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or to be of long-continued and indefinite duration” (p. 3); but this definition, they say, is increasingly subject to challenge.

The Census Bureau is yet another important source of disability definitions.  Definitions used by the Census Bureau in recent years include the definition of "work disability" in the Current Population Survey; the definition of disability in the Survey of Income and Program Participation; and the definition of disability in the American Community Survey (ACS).  Among these and other data sources that have been used by the Census Bureau, the ACS is especially useful for obtaining local data at the city and county levels.  The 2008 ACS Subject Definitions operationalize the concept of disability in a set of related questions posed to survey participants:

Using models of disability from the Institute of Medicine and the International Classification of Functioning, disability is defined as the restriction in participation that results from a lack of fit between the individual’s functional limitations and the characteristics of the physical and social environment. So while the disability is not seen as intrinsic to the individual, the way to capture it in a survey is to measure components that make up the process. The American Community Survey identifies serious difficulty in four basic areas of functioning: vision, hearing, ambulation, and cognition. Described below, the ACS asks respondents about serious difficulty and the resulting data can be used individually or combined. The ACS also includes two questions to identify people with difficulties that might impact their ability to live independently. In the 2008 American Community Survey, there are three disability questions, two with subparts totaling six questions in all . . . . (p. 38).

These various definitions, including especially that of the ACS, will be relevant to further exploration of data on disabilities within the U.S.