The words “impairment,” “disability,” and “handicap,” are often used interchangeably. They have very different meanings, however. The differences in meaning are important for understanding the effects of neurological injury on development.
The most commonly cited definitions are those provided by the World Health Organization (1980) in The International Classification of Impairments, Disabilities, and Handicaps:
Impairment: any loss or abnormality of psychological, physiological or anatomical structure or function.
Disability: any restriction or lack (resulting from an impairment) of ability to perform an activity in the manner or within the range considered normal for a human being.
Handicap: a disadvantage for a given individual that limits or prevents the fulfillment of a role that is normal
As traditionally used, impairment refers to a problem with a structure or organ of the body; disability is a functional limitation with regard to a particular activity; and handicap refers to a disadvantage in filling a role in life relative to a peer group.
Examples to illustrate the differences among the terms "impairment," "disability," and "handicap."
1. CP example: David is a 4-yr.-old who has a form of cerebral palsy (CP) called spastic diplegia. David's CP causes his legs to be stiff, tight, and difficult to move. He cannot stand or walk.
Impairment: The inability to move the legs easily at the joints and inability to bear weight on the feet is an impairment. Without orthotics and surgery to release abnormally contracted muscles, David's level of impairment may increase as imbalanced muscle contraction over a period of time can cause hip dislocation and deformed bone growth. No treatment may be currently available to lessen David's impairment.
Disability: David's inability to walk is a disability. His level of disability can be improved with physical therapy and special equipment. For example, if he learns to use a walker, with braces, his level of disability will improve considerably.
Handicap: David's cerebral palsy is handicapping to the extent that it prevents him from fulfilling a normal role at home, in preschool, and in the community. His level of handicap has been only very mild in the early years as he has been well-supported to be able to play with other children, interact normally with family members and participate fully in family and community activities. As he gets older, his handicap will increase where certain sports and physical activities are considered "normal" activities for children of the same age. He has little handicap in his preschool classroom, though he needs some assistance to move about the classroom and from one activity to another outside the classroom. Appropriate services and equipment can reduce the extent to which cerebral palsy prevents David from fulfilling a normal role in the home, school and community as he grows.
2. LD example: Cindy is an 8-year-old who has extreme difficulty with reading (severe dyslexia). She has good vision and hearing and scores well on tests of intelligence. She went to an excellent preschool and several different special reading programs have been tried since early in kindergarten.
Impairment: While no brain injury or malformation has been identified, some impairment is presumed to exist in how Cindy's brain puts together visual and auditory information. The impairment may be inability to associate sounds with symbols, for example.
Disability: In Cindy's case, the inability to read is a disability. The disability can probably be improved by trying different teaching methods and using those that seem most effective with Cindy. If the impairment can be explained, it may be possible to dramatically improve the disability by using a method of teaching that does not require skills that are impaired (That is, if the difficulty involves learning sounds for letters, a sight-reading approach can improve her level of disability).
Handicap: Cindy already experiences a handicap as compared with other children in her class at school, and she may fail third grade. Her condition will become more handicapping as she gets older if an effective approach is not found to improve her reading or to teach her to compensate for her reading difficulties. Even if the level of disability stays severe (that is, she never learns to read well), this will be less handicapping if she learns to tape lectures and "read" books on audiotapes. Using such approaches, even in elementary school, can prevent her reading disability from interfering with her progress in other academic areas (increasing her handicap).