The medical model treats disability as a problem inside a person that professionals should diagnose and fix. The social model says people are disabled mainly by barriers around them, such as inaccessible buildings, attitudes and rules. The World Health Organization (WHO), in its guide to the International Classification of Functioning, Disability and Health (ICF), describes both models and says each is only part of the picture.
These ideas are not just theory. They shape how eligibility is decided, how support plans are written and how a direct support professional spends a shift. This brief explains the two models, the blended approach most U.S. rules now reflect as of September 2026, and what it means in daily work with people with I/DD.
The medical model
WHO describes the medical model as seeing disability as a feature of the person, caused directly by disease, injury or another health condition. The response is individual treatment by professionals to correct the problem.
In I/DD services, this frame can show up when a person is described mainly by a diagnosis or IQ score, when experts set the goals, and when success means reducing symptoms or behaviors. It is not all bad: diagnosis opens the door to services, and health care matters. The risk is that the person's own goals and surroundings drop out of view.
The social model
One founding statement came from disabled activists in Britain. In November 1975, the Union of the Physically Impaired Against Segregation (UPIAS) met with the Disability Alliance and set out a clear distinction. Impairment is a condition of the body, such as a missing or affected limb or organ. Disability is the disadvantage caused by a society that takes little or no account of people with impairments and so shuts them out of mainstream life. In the group's words: "Disability is something imposed on top of our impairments by the way we are unnecessarily isolated and excluded from full participation in society."
UPIAS was writing about physical impairment, but WHO describes the social model in general terms. Under this view, the fix is to remove barriers: ramps, plain language, flexible schedules, inclusive jobs and housing, and respect for a person's choices. WHO notes the social model calls for a political response, because the problem is created by the environment and attitudes.
Comparing the models
| Medical model | Social model | Biopsychosocial (blended) model | |
|---|---|---|---|
| Where the problem sits | In the person's body or mind | In barriers in the environment and society | In the interaction between the person and their surroundings |
| Main response | Diagnosis and treatment by professionals | Remove barriers; change policies and attitudes | Both: health care where needed, plus changes to the environment |
| What it can look like in I/DD services | A plan built around reducing a behavior | Advocacy for accessible housing and jobs | A plan built on the person's goals that also covers health and support needs |
The blended approach: WHO's ICF
WHO's World Health Assembly endorsed the ICF in May 2001. WHO's guide to it puts the balance plainly: "On their own, neither model is adequate, although both are partially valid." The ICF uses what it calls a biopsychosocial model, which combines medical and social views.
In the ICF, disability is the result of interaction between a health condition and contextual factors. It looks at three levels:
- Body functions and structures, where problems are called impairments
- Activities, meaning doing a task, where problems are called activity limitations
- Participation, meaning involvement in life situations, where problems are called participation restrictions
Environmental factors, such as attitudes, buildings, laws and social structures, can act as barriers or facilitators. Personal factors such as age, background and past experience also shape how disability is experienced.
The UN Convention on the Rights of Persons with Disabilities, adopted by the UN General Assembly in December 2006, takes a similar interactional view. Its preamble says disability results from the interaction between people with impairments and barriers of attitude and environment. Its Article 19 recognizes the equal right of people with disabilities to live in the community, with choices equal to others.
Where the models show up in U.S. rules
U.S. law mixes both views.
- Eligibility definitions lean on impairment. The federal Developmental Disabilities Act defines a developmental disability as a severe, chronic disability that begins before age 22 and causes substantial limits in 3 or more of 7 life areas, such as self-care, learning, mobility and capacity for independent living. The Americans with Disabilities Act defines disability around an impairment that substantially limits a major life activity.
- Professional definitions add supports. The American Association on Intellectual and Developmental Disabilities (AAIDD) defines intellectual disability as significant limits in intellectual functioning and adaptive behavior that begin before age 22. It also says limits often coexist with strengths, and that a person's functioning will improve with the right personalized supports over time.
- Facility rules use treatment language. Federal rules for an ICF/IID require each resident to receive a continuous program of active treatment aimed at as much self-determination and independence as possible.
- Community rules lean toward choice. For Medicaid home and community-based services, federal rules require person-centered planning that the individual directs as much as possible, with people the person chooses. The written plan must reflect the person's strengths and preferences, along with clinical and support needs.
That last rule is the blended model in one sentence: health and support needs are part of the plan, but the person's goals and choices lead it.
Why this matters for providers and DSPs
- It changes the first question. A medical frame asks what is wrong with the person. A social or blended frame asks what is getting in the way and what support would help. The second question can point to changes staff can make during a shift.
- Look at the setting, not just the behavior. Checking noise, crowding, routines, staff approach and unmet needs applies the social model's focus on surroundings, and keeps every problem from being treated as a symptom.
- Plans must reflect the person. HCBS rules require the person-centered service plan to reflect strengths, preferences and goals. DSP notes and observations feed that plan, so write about what the person wants and what works, not only incidents.
- Health still matters. The blended model does not dismiss medical needs. Medications, seizures and other health conditions remain part of good support.
- Words carry the model. Describing someone as a person with goals and preferences, rather than by a diagnosis or a list of behaviors, keeps the person at the center of records and conversations.
For how the move away from institutions happened, see Institutions to community. For the legal right to community living, see Olmstead v. L.C.. For more on the DSP role, see What is a DSP?