Understanding Depression as It Occurs in the Context of Post-Traumatic Stress Disorder

The aim of the current special issue is to gain a better understanding of depression as it occurs in the context of posttraumatic stress disorder (PTSD). Depression and major depressive disorder (MDD) are often present in the context of PTSD, but it is not clear whether the high prevalence of depressive disorders in PTSD should be best understood as true comorbid conditions, with a separate underlying cause and pathophysiology or rather, whether it should best be considered an artifact of overlapping symptoms. Indeed, when individuals with PTSD also meet criteria for depression, this may signal the presence of a single depressive subtype of PTSD rather than two separate syndromes. Epidemiologic data support the idea that a depressive diathesis can be a risk factor for the development of PTSD following trauma exposure. However, the question of childhood trauma as an even earlier antecedent of depression suggests that the depression that contributes to PTSD risk may relate to earlier forms of trauma exposure rather than genetic diatheses per se. Prospective studies assessing the development of major depressive disorder (MDD) show that, although the prevalence of PTSD is higher shortly after exposure, later on approximately the same prevalences of PTSD and MDD are seen after exposure to traumatic events. Severe depressive symptoms in the early aftermath of trauma exposure can be considered more relevant in predicting an unfavorable course of mental health than severity of PTSD symptoms, underlining the relevance of broad mental health assessment after trauma exposure. Whether depression in PTSD represents a phenomenological expression of the same underlying pathophysiology becomes interesting to consider in the context of the rather distinct biological alterations that have been observed in PTSD and major depressive disorder, particularly in the context of neuroendocrine, neurochemical, and brain metabolic factors. Beside clinical characteristics, biological markers may help to further improve identification of biologically distinct endophenotypes and, ultimately, to devise more specific treatment strategies. Although antidepressants are among the only FDA-approved pharmacological treatments for PTSD, these medications have only limited utility in PTSD, and it is not clear whether the efficacy of these agents results from the treatment of comorbid depression or PTSD per se.