ويعني هذا التصنيف ضمنيا أن ثمة علاقة سببية بين العاهات وحالات العجز والإعاقة لا تنشأ عن العوامل البيئية التي تؤثر فعلا في انتشار حالات العجز في المجتمعات(19).
WHO-ICIDH is based on the health experience; its aim is to describe the consequences of disease, injury or disorder at the level of specific body function (biomedical status), of the person (body structures and functions) or of society (impairment, disability and handicap).18 WHO-ICIDH implies a causal link between impairment, disability and handicap unmediated by environmental factors, which do in fact influence the incidence of disability in society.19