The biopsychosocial model of illness: a model whose time has come.

The biopsychosocial model outlined in Engel's classic Science paper four decades ago emerged from dissatisfaction with the biomedical model of illness, which remains the dominant healthcare model. Engel's call to arms for a biopsychosocial model has been taken up in several healthcare fields, but it has not been accepted in the more economically dominant and politically powerful acute medical and surgical domains. It is widely used in research into complex healthcare interventions, it is the basis of the World Health Organisation's International Classification of Functioning (WHO ICF), it is used clinically, and it is used to structure clinical guidelines. Critically, it is now generally accepted that illness and health are the result of an interaction between biological, psychological, and social factors. Despite the evidence supporting its validity and utility, the biopsychosocial model has had little influence on the larger scale organization and funding of healthcare provision. With chronic diseases now accounting for most morbidity and many deaths in Western countries, healthcare systems designed around acute biomedical care models are struggling to improve patient-reported outcomes and reduce healthcare costs. Consequently, there is now a greater need to apply the biopsychological model to healthcare management. The increasing proportion of healthcare resource devoted to chronic disorders and the accompanying need to improve patient outcomes requires action; better understanding and employment of the biopsychosocial model by those charged with healthcare funding could help improve healthcare outcome while also controlling costs.