Disability is any physical, mental, sensory, or psychological impairment or deficiency resulting in the lack, loss, or substantial reduction of the ability to perform some normal function.

Disability is any impairment caused as a consequence of a cognitive, congenital, developmental, emotional, pathological, physical, sensory, traumatic problem, or a combination of any of these. The severity of disabilities varies widely. In fact, the World Health Organization (WHO), specifically its International Classification of Functioning, Disability and Health (ICF), states that all impairments, activity limitations, and participation restrictions are covered under the general term of disabilities. The WHO defines impairments as any problem of function or structure within the body, while activity limitation is considered any difficulty that an individual has while performing any action or task. A participation restriction is defined by the WHO as any problem encountered by an individual while trying to perform any of a number of daily life activities.

In the United States, the term disability is legally defined in the Rehabilitation Act (PL 93-112; 29 U.S.C. 794) amendments of 1974 and the Americans with Disabilities Act (PL 101-336; 42 U.S.C. 12101) of 1990 as a physical or mental impairment that substantially limits one or more of the major life activities of an individual.

Physical disabilities include blindness, deafness, deformity, muscular and nervous disorders, paralysis, and loss of limbs. Paralysis is frequently caused by injuries to the spinal cord, with the extent of paralysis depending on the portion of the spine that is injured. Congenital disabilities include spina bifida, cystic fibrosis, and muscular dystrophy. Other causes of disabilities include cerebral hemorrhage, arthritis and other bone diseases, amputation, severe pulmonary or cardiac disease, nerve diseases, and the natural process of aging. Mental impairments are of two types: mental illness and mental retardation.


According to the WHO, more than one billion (about 15%) of the people around the world have some type of disability. Of this number, between 110 million (2.2%) and 190 million (3.8%) are considered to have significant difficulties in functioning on a daily basis.

In the United States, it is estimated that over 35 million people are disabled. The numbers (and percentages) of disabled people in the United States and the worldwide are increasing due to an aging population in most countries and the frequency of more serious medical conditions. In addition, most disabled people have less access to healthcare services than do nondisabled people. The percentage is higher in developing countries (76–85%) than it is in developed countries (35–50%).

Professional help

Professionals, including physicians, physical and occupational therapists, social workers, and psychologists, assist disabled persons in the rehabilitation process, helping them function at the highest possible physical, vocational, and social levels. Specialists in rehabilitation medicine, sometimes referred to as physiatrists, diagnose patients and plan individual treatment programs for the management of pain and disabilities resulting from musculoskeletal injuries. People with hearing or vision loss require special education, including instruction in lip reading, sign language, or Braille.

Physical rehabilitation for individuals with musculoskeletal disabilities includes passive exercise of affected limbs and active exercise for parts of the body that are not affected. Occupational training, including counseling, helps persons whose disabilities make it necessary for them to find new jobs or careers. Rehabilitation also involves the services of speech pathologists, recreational therapists, physical therapists, home planning consultants, orthotists and prosthetists, driver educators, and dieticians.

Technological advances

Technological advances—especially those involving computer-aided devices—have aided immeasurably in mainstreaming the disabled into many areas of society. These include voice-recognition aids for the paralyzed, optical character-recognition devices for the blind, sip-and-puff air tubes that enable quadriplegics to type and control wheelchair movements with their mouths, and computerized electronic grids that translate eye movements into speech.

Mobility limitations

In addition to access, mobility for the disabled is an area of concern. The American Automobile Association (AAA) estimates that there are more than 500,000 licensed drivers in the United States with significant physical impairments and another 1.5 million with lesser disabilities. AAA auto clubs throughout the country work to improve the mobility of disabled drivers and travelers through improved driver education for those with impairments and improved facilities for the handicapped traveler, including motorist rest areas on the highway.


Public attitudes toward the disabled have changed. Between the 1970s and the early 2000s, advocates for the disabled won passage of numerous laws on the federal, state, and local levels aimed at making education, employment, and public accommodation more accessible through the elimination of physical barriers to access, as well as affirmative action in the hiring and professional advancement of disabled people.


The United Nations (UN) General Assembly adopted the Convention on the Rights of Persons with Disabilities on December 13, 2006. This international human rights treaty, which was developed by people with disabilities, government officials, members of nongovernmental organizations, and others representing the international community, was ratified on May 3, 2008. As of July 2015, the UN had persuaded 156 countries and the European Union to sign the document. According to the UN, the definition of people who are disabled is “those who have long-term physical, mental, intellectual or sensory impairments which in interaction with various barriers may hinder their full and effective participation in society on an equal basis with others.”

Article 1 of the treaty states the purpose of the Convention is: “to promote, protect and ensure the full and equal enjoyment of all human rights and fundamental freedoms by all persons with disabilities, and to promote respect for their inherent dignity.” The eight principles that form the foundation of the treaty are:

Two major pieces of federal legislation in the United States have protected the rights of the disabled: a 1975 law guaranteeing disabled children a right to public education in the least restrictive setting possible and the 1990 Americans with Disabilities Act (ADA), which extends comprehensive civil rights protection in employment and access to public areas.

Title I of the ADA, which prohibits discrimination by private employers on the basis of disability, is intended to ensure that the same performance standards and job requirements are applied to disabled persons as to persons who are not. In cases in which functional limitations may interfere with job performance, employers are required to take any necessary steps to accommodate reasonably the needs of a disabled person, including adjustments to the work environment or to the way in which the job is customarily performed. The ADA also contains provisions ensuring nondiscrimination in state and local government services (Title II) and nondiscrimination in public accommodations and commercial facilities (Title III).


A writing system, written on embossed paper, which is used by the blind and visibly impaired.
A medical professional responsible for and dealing with orthoses; that is, any material or instrument used to control, move, or immobilize a joint or body segment or any of the body's extremities.
A medical profession responsible for and dealing with prostheses; that is, the fitting of artificial/residual limbs of the upper and lower extremities of the body.

In 2015, proponents of the ADA celebrated 25 years since it was first place into law. The article “Disability Act Marked Turnaround 25 Years Ago, but Work to Be Done” in the Chicago Tribune recounts what it was like for the disabled before the ADA. Rachel Crosby, the author of the article, describes the situation for Marco Bristo, a disabled resident of Chicago, Illinois: “It was a time when buses didn't kneel for wheelchairs and curbs weren't cut into ramps. That grocery store a block and a half from her house. Impossible to get to. And if she wanted to go out for dinner, front steps were impassable mountains, and front doors were rarely wide enough.”

All of that has now changed. Buses and trains now are fully accessible for the disabled. Curbs have been cut to allow the disabled to navigate from one sidewalk to another. Annie Michales, another disabled Chicagoan, made the following comment about the creator of the ADA: “Whoever thought of the disabilities act, I applaud that person.”

See also Learning disability ; Reading disability .



Burch, Susan, and Michael Rembis, eds. Disability Histories. Urbana: University of Illinois Press, 2014.

Dunn, Dana S. The Social Psychology of Disability. Oxford: Oxford University Press, 2015.

Kanter, Arlene S. The Development of Disability Rights under International Law: From Charity to Human Rights. Abingdon, Oxon, UK: Routledge, 2015.


Lansing, Michael J. “Making Disability an Essential Part of American History.” OAH Magazine ofHistory 23, no. 3 (July 2009): 11–15.


Crosby, Rachel. “Disability Act Marked Turnaround 25 Years Ago, but Work to Be Done.” Chicago Tribune. http://www.chicagotribune.com/news/local/breaking/ct-ada-25chicago-disability-resources-met-20150721-story.html (accessed August 16, 2015).

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World Health Organization. “Disabilities.” http://www.who.int/topics/disabilities/en/ (accessed August 16, 2015).

World Health Organization. “Why Is the Convention on the Rights of Persons with Disabilities Important?” http://www.who.int/features/qa/67/en/ (accessed August 16, 2015).


National Organization on Disability, 77 Water St., Ste. 204, New York, NY, 10005, (646) 505-1191, Fax: (646) 5051184, info@nod.org, http://nod.org .

U.S. International Council on Disabilities, 1012 14th St. NW, Ste. 105, Washington, DC, 20005, (202) 347-0102, Fax: (202) 347-0351, http://www.usicd.org .