FIGURE 1. Interaction between the components of ICF.

activities, and on participation in society, but these three components of functioning can have a multidirectional impact on each other and on the health condition as well (Figure 1). Prior to the Americans with Disabilities Act of 1990 (ADA) people with ill health or with a disability were often limited in their participation in society. For example, an individual with a mobility disability might not have been hired for a job for which she or he was otherwise qualified. In this example, the ADA can be understood as an environmental factor that facilitates the reduction of barriers to participation in work.

The ICF is also seen as a dynamic, not a static, model. The components, domains, and items may be impaired, limited, or restricted either temporarily or permanently. Impairments, limitations, and restriction may be progressive, regressive, or static, and intermittent or continuous. The temporal quality is not fixed by ICF. The deviation from the norm may be slight or severe and may fluctuate in degree over time. ICF does not specify a threshold for the degree of deviation from the norm for a determination of disability status. It can be applied to legal definitions or program criteria and used to put them into operation.

The SSA’s statutory definition of disability, some sequential evaluation components, and even the basic premise of SSA’s disability benefits can readily be mapped onto this interactive conceptual model. For example, in SSA’s definition of disability there must be a medically determinable physical or mental impairment that causes the inability to work. SSA’s requirement for the impairments is that they either result in death or last at least one year; this is consistent with the ICF model. Addition-

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