environmental and personal factors
Two people use exactly the same wheelchair. One lives in a town of ramps, lifts, wide doors, and welcoming employers, and gets to work, the shops, and friends every day. The other lives up three flights of stairs, in a town with no curb cuts and a job that will not adapt, and is effectively trapped at home. Same body, same chair, opposite lives. What changed everything was the context, and the ICF gives context its own two components: environmental factors and personal factors.
Environmental factors are everything in the world outside the person that affects functioning: the physical world (stairs, ramps, terrain, lighting), products and technology (wheelchairs, hearing aids, medications), the social world (family, friends, employers, support services), and attitudes (prejudice, or acceptance). Crucially, environmental factors can be facilitators, which make functioning easier, or barriers, which make it harder, and the same thing can be either, money is a facilitator when present and a barrier when absent. Personal factors are the features of the individual that are not part of the health condition: age, sex, character, education, coping style, life experience, habits, culture. The ICF lists personal factors but, because they vary so much across societies, does not formally classify them.
These factors matter because they are the part of disability we can often change fastest and most cheaply. We may not be able to repair a spinal cord, but we can install a ramp, change an attitude, fund a support worker, or modify a job, and thereby reduce disability dramatically. This is the heart of the social model of disability woven into the ICF: disability is not only inside the person but also in the fit between the person and the world. The caveat is that personal factors are double-edged, a stubborn, optimistic temperament can power a recovery, while depression or isolation can quietly defeat the best therapy plan.
A wheelchair user's office installs a ramp and a lift (environmental facilitators) and reassigns him from a warehouse to a desk role; his disability falls sharply even though his spinal cord injury, and his impairment, are unchanged.
Often the cheapest way to cut disability is to change the world, not the body.
The same factor can be a facilitator or a barrier. A family can speed recovery by encouraging independence, or slow it by doing everything for the person; the environment is not automatically helpful.