Stress, immunity and illness--a review.

Psychological factors have long been thought to play a contributing role in either the predisposition, onset or course of various physical illnesses. Recently, rapid advances in immunology have created interest in the interaction between psychosocial factors, behaviour and the immune system. This paper reviews some of the models proposed to explain the relationship between psychological variables and physical illness and presents evidence for a contribution of psychological factors to certain illnesses in which abnormalities in immunologic state are thought to be important. From a somewhat different perspective, animal studies have demonstrated complex effects of stress, on disease susceptibility. Recent human studies have demonstrated consistent immunologic changes in people undergoing acute naturally occurring psychological stress such as bereavement or an important examination. In humans, the effects of chronic stress may be different from acute stress, corresponding to the findings in animals. Abnormalities in immunologic functioning and physical illness are reviewed for different psychiatric disorders--depression, anorexia nervosa and schizophrenia; depression is the only disorder which consistently demonstrated immunologic changes. Possible mechanisms for the stress/immune-change relationship are suggested.