New wine in old bottles: the WHO ICF as an explanatory model of human behaviour.

The World Health Organization's International Classification of Functioning (WHO ICF) is a good but incomplete framework for describing the situation of someone with long-term ill health. Several deficiencies exist for which improvements are suggested. The WHO needs to integrate the ICF with the ICD-10 to form a comprehensive system of classification of illness. Words are needed for normality at the level of organ and person, and the words 'histology' and 'physiology', and 'anatomy' and 'capacity' are suggested for the two levels respectively. A fourth context, that of time, is needed to understand fully a person's situation. The classification framework needs to take more account of the patient. It needs to recognize two separate perspectives, that of the subject and that of external observers and it needs to recognize two other specific person-centred phenomena: free will and quality of life. With changes and additions to take account of these deficiencies, the WHO ICF can be used as a powerful analytic and explanatory model of human experience and behaviour in any situation, not only in illness and disease.