Depression and cancer: challenging the myth through epidemiology

Three recent meta-analyses involving well-powered prospective studies found evidence for a weak association between depression, especially chronic, and both cancer onset and cancer survival. These associations reach statistical significance but effect sizes are small, challenging their clinical significance. The underlying mechanisms of these associations are likely to involve some confounders (i.e. factors that may promote both depression and cancer onset or mortality without any direct link between the two variables), as well as both behavioral and biological mediators (i.e. correlates of depression that may in turn lead to an increased risk of cancer or to poorer outcome). Further studies are needed to explore the clinical implications of these associations.