Atypical depression, by definition, is characterized by mood reactivity, hypersomnia, and increased eating, in contrast to the lack of mood reactivity, insomnia, and loss of appetite seen in endogenous depression. Subjects with atypical depression thus provide a natural comparison group for linking particular vulnerability factors with endogenous depressive subtypes. Using this latter approach in a community-based sample of 653 individuals with major depression, we previously demonstrated a significant association between early childhood physical and/or sexual abuse and atypical but not endogenous symptoms of depression (3). Biological studies also point to a mechanistic link between atypical depression and severe trauma. More specifically, low baseline cortisol levels and hypersensitivity to low doses of dexamethasone have been found in both posttraumatic stress disorder (4) and atypical depression (5, 6), consistent with a hypothalamic-pituitary-adrenal (HPA) axis that is hyperregulated. In contrast, a large body of work has demonstrated hypercortisolemia and resistance to dexamethasone in endogenous depression, consistent with a stress response that is chronically overactivated and hyporegulated (7). This further suggests that severe trauma is more closely linked with atypical than endogenous depressive symptoms.