Definitions of sickness, illness and disease Although the terms are often used interchangeably, sickness, illness and disease have different meanings that reflect different perspectives. Disease is an objective term referring to diagnosable abnormalities in organs, body systems or physiology. Illness is a subjective term referring to an individual’s experience of mental and physical sensations or states, and may not necessarily indicate the presence of disease. Sickness encompasses both disease and illness. The difference between illness and disease was summarised by Cassell (1976): “Illness is what the patient feels when he goes to the doctor, disease is what he has on the way home” (p.53). The view of illness as a social role is based on the premise that the behaviour of patients, doctors and carers is related to social perceptions or constructs of sickness.
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