Illness and Disease

Illness and disease are overlapping, but distinct, constructs. Whereas disease refers to constellations of symptoms that define a diagnosable physical or psychiatric disorder, illness refers to the subjective experience of poor health. Illness manifests itself as somatic (bodily) or psychological symptoms, but may stem from multiple sources—including cognitive and social processes—and may or may not reflect the presence of an underlying disease (Kleinman, 1988). The relationship of illness to disease is complex. A person may experience ill health with no underlying disease. Conversely, he or she may suffer from an underlying disease without perceiving himself or herself as ill (Weiner, 1992).