Environmental stress and psychiatric illness.

It has long been recognized that environmental stress plays a pivotal role in the pathogenesis of psychiatric disorders. The relationship is complex and the neurobiological mechanisms that mediate the contribution of stressful experiences to the manifestation of illness are not well understood. In considering this relationship, it is important to differentiate between the role of environmental stressors as vulnerability factors that predispose the individual to psychiatric illness and may be temporally distant from its clinical onset, and their role as direct precipitants of the illness. Furthermore, environmental stressors must be considered in the context of constitutional vulnerability factors, such as genetic predisposition, with which such stressors may interact. Genetic predisposition may influence not only vulnerability to illness but also the nature of the individual's response to stress and the likelihood of exposure to stressful events. In this paper, we focus on two areas that illustrate the complexity of the field and the important findings that have emerged--the role of early parental loss (EPL) in adult psychopathology, particularly major depression, and the relationship between recent significant life events and depressive episodes. We conclude with a preliminary conceptual framework for considering the relationship between genetic susceptibility and environmental stress in the pathogenesis of psychiatric illness.