Chronic illness and depressive symptoms in late life.

The relationship between illness and depressive symptoms is examined using a large, nationally representative, and longitudinal sample of Americans over the age of 50. Seven illnesses (cancer, stroke, heart condition, chronic obstructed pulmonary disease, diabetes, high blood pressure, and arthritis) and three forms of disability (activities in daily living, mobility, and strength) substantially increase symptoms. Yet, most of these positive effects diminish with age. Multiplicative interactions between age and illness indicate that those who develop chronic illnesses earlier in life tend to report more depressive symptoms than do those who develop them later. Similarly, disability leads to more depressive symptoms when experienced at younger ages. This age-graded effect emerges even for illnesses that are known to share a biological substrate with depression (e.g. vascular disorders). The results are discussed with respect to theories of illness, depression, and aging.