Invited commentary: Stress and mortality

In this issue of the Journal, Nielsen et al. (Am J Epidemiol 2008;168:481-91) use data from a large Danish study to provide evidence that self-reported stress is associated with increased all-cause mortality over the next 20 years. The finding is remarkable. In this commentary, the authors explore what is really meant by stress; they argue that it would be naive to view stress as reported in this way, with some external exposure. It has to be seen through the lens of the participant's personal experience, and this lens is likely to be clouded by personality, coping styles, and the common mental disorders-depression and anxiety. The authors discuss a wider literature concerning similar findings associating depression with mortality, suggesting three broad reasons for the association. First, the findings might be explained by the impact of stress or distress on well-established risk factors for cardiovascular disease and cancer. Second, there might be direct, underlying psychosomatic pathways by which stress or distress can affect immune or autonomic function. Third, there might be common causal pathways-shared genes or early adversities that predict both stress and mortality from other causes independently. The authors suggest that life course epidemiologic research is required to test these competing hypotheses.