ebruary 2, 2015; Accepted: May 2, 2015; Published: June 8, 2015
Copyright: © 2015 Meloni et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Data Availability: All relevant data are within the paper and its Supporting Information files (S1 File Dataset).
Funding: The authors received no specific funding for this work.
Competing interests: The authors have declared that no competing interests exist.
The models of disability are categorical representations from which social relations are developed, built, and understood. They are common structures for making sense of the complex phenomena of disability [1, 2]. As a cognitive organizer, a model of disability helps people to identify and explain social reaction to human, biological, and social diversity. Hence, it offers social frames  where expected behaviors and social identities are represented, helping people to make decisions and judgments .
To date, the scientific literature has identified three main disability models: individual (taken to include the medical model), social, and biopsychosocial [5, 6]. The individual model is clearly defined in Nagi’s pathological model from the 1960s [7, 8]. However, its relevance was questioned by the social model that was developed within the Marxist dialectical approach of the 1960s and 1970s [5, 9, 10]. Later, those two models were integrated into the biopsychosocial model using influences from transdisciplinary approaches and theories—i.e., integrated complexity  and system theory [12, 13] in addition to cybernetics . The biopsychosocial model avoids both the strict biological reductionism of the individual model and the socio-cultural determinism of the social model. The model also uses and finds the most authoritative and practical application in the International Classification of Functioning, Disability and Health (ICF; ).
The scientific community has adopted the individual and social model as alternative and opposite descriptions of human functioning and health conditions [5, 6, 9, 15–17]. Conversely, the biopsychosocial model is often meant as an integration of the two opposing models: individual and social . The individual model claims that disability is a direct consequence of disease, trauma, or other health conditions. Therefore, disability is viewed as “something imposed on top of […] impairments by the way [… disabled people] are unnecessarily isolated and excluded from society” (see p. 4 ). Hence, the disability is a problem of the individual, that is, as an individual’s deviation from the biomedical norms of structure or function that requires medical care treatments provided by health professionals. For this reason, the individual model was also defined as a medical model of disability [6, 9, 17, 19]. In disability studies, all models that define disability as being outside of religious, ethical, or aesthetic norms are encompassed within the individual model [20–22]. Therefore, every time we refer to the individual model, we also mean to include the medical one.
Conversely, from the individual model, the social model portrays disability as a political issue, created by the social environment. Physical barriers or social attitudes are considered the origin of disability, preventing access to virtual and real spaces or making social participation difficult for people with diversity in functioning. Consequently, a disability is not an attribute of an individual, but rather a complex collection of conditions, requiring social actions rather than just medical treatments .
Finally, since 2001, the ICF has used a biopsychosocial—also called interactive —model of human functioning and health which represents an integration of the two conflicting models (medical and social). To achieve this “synthesis” (see p. 28 ), the disability is not a consequence of disease but the outcome of triadic causation of three variables related to human hea