Introduction

Cultural and professional models of illness influence decisions on individual patients and delivery of health care. The biomedical model of illness, which has dominated health care for the past century, cannot fully explain many forms of illness. This failure stems partly from three assumptions: all illness has a single underlying cause, disease (pathology) is always the single cause, and removal or attenuation of the disease will result in a return to health. Evidence exists that all three assumptions are wrong. We describe the problems with current models and describe a new model, derived from the World Health Organization's international classification of functioning framework,1 2 that provides a more comprehensive, less biologically dependent account of illness.

Importance of models for understanding illness

The model of illness adopted by society can have important consequences. In the first world war, for example, soldiers complaining of symptoms after experiencing severe stresses were sometimes shot as malingerers, but today they are considered victims and eligible for financial settlements Social acceptance that a behaviour or reported symptom constitutes an illness bestows privileges on an individual and formal duties on society.3

Currently, most models of illness assume a causal relation between disease and illness—the perceived condition of poor health felt by an individual. Cultural health beliefs and models of illness help determine the perceived importance of symptoms and the subsequent use of medical resources.4 The assumption that a specific disease underlies all illness has led to medicalisation of commonly experienced anomalous sensations and often disbelief of patients who present with illness without any demonstrable disease process.

Current models of illness

Despite their importance, models of illness are rarely explicitly discussed or defined. The often criticised but nevertheless dominant 20th …