The New IOM Model: Advancing Disability Rehabilitation

For decades, disability was treated as a one-way road – a person experienced pathology, developed impairments, and eventually became disabled, with little expectation of reversal. That view began to shift with the 1991 Institute of Medicine (IOM) report Disability in America, but it was the 1997 IOM report Enabling America that truly transformed how rehabilitation professionals think about disability. The revised model it introduced – commonly called the New IOM Model – reframed disability not as a fixed endpoint but as a dynamic state that can be influenced, and even reversed, through the right interventions and environmental conditions.

From prevention to rehabilitation: why the original model needed revision 🔗

The 1991 IOM model was groundbreaking for its time. It identified pathology, impairment, functional limitation, and disability as stages of a disabling process and introduced the role of risk factors in influencing that process. However, as subsequent analysis noted, it had a critical structural flaw: its arrows pointed only in one direction – toward greater disability. The unidirectionality implied by the model’s arrows, which pointed only toward the condition of disability, was a shortcoming that needed correction, especially in the context of rehabilitation.

There were two additional limitations. The 1991 model gave a limited characterization of the environment and the interaction of the individual with the environment, and also provided a limited representation of societal limitations. Since the original model was designed with disability prevention in mind rather than rehabilitation, the 1997 committee set out to fix these gaps – and the result was a substantially upgraded framework.

Bidirectional arrows: reversing the disabling process 🔗

The most immediately visible change in the New IOM Model is the introduction of bidirectional arrows between the stages of the enabling-disabling process. These bidirectional arrows indicate that the disabling process can be reversed with proper interventions – what the model calls the enabling process. This was a conceptual shift of real significance: for the first time, the model visually and theoretically acknowledged that rehabilitation could move a person backward through the stages, from disability toward restored function.

Alongside the bidirectional arrows, the New IOM Model introduced a new category: “no disabling condition.” This addition was included to indicate that complete rehabilitation is feasible – a direct challenge to assumptions that disability is always permanent or progressive. Consider someone who suffers a spinal injury and initially loses significant motor function. Under the old linear model, the focus would have been on managing that disability. The new framework, by contrast, holds open the possibility of substantial recovery, and positions rehabilitation as the mechanism that can make that recovery happen.

Critically, the graphic representation of the new IOM model did not include a box for “disability,” in an effort to help clarify the fact that disability is not inherent in the individual, but rather is a product of the interaction of the individual with the environment. This was a deliberate choice – removing “disability” as a fixed category reinforces the model’s relational view of what disability actually is.

Three-dimensional representation: the person-environment interaction 🔗

One of the most theoretically sophisticated contributions of the New IOM Model is its three-dimensional depiction of the relationship between a person and their environment. The enabling-disabling process is depicted as being an active part of the individual person, while the physical and social environments are depicted as a three-dimensional mat, with social factors on one side and physical factors on the other. This is a far more nuanced picture than the older linear diagrams offered.

Access to the environment represents both physical space and social structures – family, community, and society. A person who does not manifest disability is fully integrated into society and has full access to both social opportunities such as employment, education, and leadership roles, and physical space including housing, workplaces, and transportation. A person with disabling conditions has increased needs and is dislocated from their prior integration into the environment.

This concept of environmental displacement is central to understanding how the model works in practice. Disability, in this framework, is not a property of the person – it is the gap between a person’s capabilities and what their environment demands or allows. Disability is the expression of the gap between a person’s capabilities and the demands of the environment – the interaction of a person’s limitations with social and physical environmental factors. Many disabling conditions are thus preventable or reversible with proper and adequate rehabilitation, including environmental modification.

The rehabilitative process attempts to rectify this displacement, either by restoring function in the individual or by expanding access to the environment – for example, by building ramps. The most effective rehabilitation programs include both approaches, and the model illustrates that disability is the interaction between potentially disabling conditions of an individual and the environment, so strategies that affect the environment or the pertinent potentially disabling conditions both target disability.

Why three dimensions matter 🔗

The identification of three dimensions – the individual, the environment, and the individual-environment interaction – clarifies the role played by all three within the process of disablement and introduces major hints for further considerations on how to create virtuous processes of enablement. In practical terms, this means rehabilitation cannot be evaluated by looking at an individual in isolation. A person with a mobility impairment who lives in a fully accessible home with strong social support may experience far less disability than another person with a less severe impairment living in an inaccessible environment with no support network. The model makes this visible in a way earlier frameworks did not.

Transitional factors: what drives change along the continuum 🔗

The New IOM Model doesn’t just show that movement between stages is possible – it explains what drives those transitions. The environment interacts at all points in the process; recent research on disability and rehabilitation has described the constituent parts of the environment in as much detail as Nagi’s model gave to the individual pathway. These constituent factors are grouped into two broad categories: risk factors and enabling factors.

Risk factors include biological factors, external environmental factors (social and physical), behavioral and lifestyle-related risk factors, and psychological aspects such as the acceptance of one’s impairment. Environmental factors comprise aspects such as income, support networks, and access to healthcare. When risk factors dominate – for instance, when a person lacks access to rehabilitation services, lives in a structurally inaccessible environment, or faces attitudinal discrimination – the disabling process progresses. When enabling factors dominate – access to timely medical care, strong social support, inclusive design – the enabling process gains ground.

The social and psychological environment 🔗

The environment is now understood to include the economic system, culture, political system, and psychological factors as well as the natural and the humanly constructed environment. This is a broad and deliberately inclusive definition. The social environment is conceptualized to include cultural, political, and economic factors. The psychological environment is the intrapersonal environment, and both affect the disabling process. For example, cultural attitudes toward disability can determine whether a functional limitation is even recognized as limiting – and whether rehabilitation resources are sought or offered. Two people with identical clinical profiles may experience vastly different levels of disability depending on where they live and what attitudes surround them.

The model also introduced the concept of secondary conditions – defined as any additional physical or mental health condition arising from a primary disabling condition, which often increase the severity of disability but are also highly preventable. This addition underscores the importance of proactive, comprehensive care that does not wait for complications to develop.

Implications for rehabilitation practice 🔗

The New IOM Model does more than offer a theoretical framework – it directly shapes how rehabilitation professionals should structure their work. These models are used in classroom instruction for physical therapists, social workers, clinical psychologists, and psychotherapists, as well as nursing and medical students , and for good reason: they provide a shared language and a shared set of goals.

Assessment must go beyond the individual 🔗

Because the model positions disability as a product of person-environment interaction, a thorough rehabilitation assessment must evaluate environmental barriers and supports alongside individual impairments. Methods for quantifying disability should be developed that are sensitive to the characteristics of both the person and the environment, facilitating research into the factors that affect transitions between disability and other states of the enabling-disabling process, and the development of effective preventive and rehabilitative intervention strategies. In clinical terms, this might mean assessing the layout of a patient’s home, the availability of community resources, their family’s capacity to support recovery, and potential barriers at their place of work – not just their physical or cognitive status at the time of assessment.

Dual-track intervention: the individual and the environment 🔗

The model’s three-dimensional structure makes clear that interventions can and should operate on two tracks simultaneously. On one track, clinicians work to restore function in the individual through physiotherapy, cognitive rehabilitation, medication, or other therapies. On the other track, they work to expand environmental access – recommending assistive technologies, advocating for workplace modifications, or supporting family and community networks. Environmental strategies can be effective in helping people function independently and not be limited in their social participation, in work, leisure, or social interactions as a spouse, parent, friend, or coworker.

Shaping policy and systemic change 🔗

At a broader level, the New IOM Model has significant implications for disability policy. By demonstrating that environmental factors can create or eliminate disability, it provides a compelling argument for investment in accessible infrastructure, inclusive design, and well-resourced community support systems. Previous models that viewed pathology and disability interchangeably and excluded consideration of the environment have been replaced by models in which disability is seen to result from the interaction between the characteristics of individuals with potentially disabling conditions and the characteristics of their environment. This shift in thinking has downstream effects on legislation, healthcare funding priorities, and the design of public spaces.

The model also reframes the goals of rehabilitation research. Disability research should be explicitly focused on the effects of the environment in producing or reducing disability. This means funding and attention need to go not only toward developing better clinical treatments but toward understanding what makes environments disabling – and how to change them.

A framework built for complexity 🔗

What makes the New IOM Model durable is that it honestly reflects how complex disability actually is. It does not promise simple solutions or uniform outcomes. Instead, it gives practitioners, researchers, and policymakers a structured way to think about the many variables at play: the person’s biology, their behavior and lifestyle, the physical environment around them, the social and cultural context they inhabit, and the quality of care and support they can access. Each of these is a potential point of intervention. Each is also a potential source of risk.

By replacing a unidirectional, individual-focused model with one that is bidirectional, relational, and three-dimensional, the 1997 IOM revision gave the field of rehabilitation a framework that is both more scientifically accurate and more practically useful. It acknowledged what experienced clinicians already knew: that with the right conditions, people can and do recover – and that creating those conditions is as much a matter of changing the environment as it is of treating the individual.

What do you think? When rehabilitation focuses primarily on restoring individual function rather than modifying the environment, which populations are most likely to be underserved – and why? And if disability is fundamentally a person-environment mismatch rather than an individual deficit, how should that change the way we train rehabilitation professionals?

References

1. https://nap.nationalacademies.org/read/5799/chapter/2
2. https://nap.nationalacademies.org/read/11859/chapter/4
3. https://www.ncbi.nlm.nih.gov/books/NBK233564/