The concept of post-traumatic mood disorder.

Post-traumatic stress disorder (PTSD) is frequently comorbid with depression. A number of studies have been conducted to compare individuals suffering from comorbid PTSD and depression with individuals suffering from PTSD alone or depression alone. Comorbidity of PTSD and depression is associated with more severe symptoms as well as higher levels of disability compared to individuals with PTSD alone. A severity of overall symptoms is three to fivefold greater in subjects with comorbid PTSD and depression compared to those with PTSD alone. The comorbid group is five times more likely to manifest functional impairment compared to those diagnosed with PTSD alone. Patients with comorbid PTSD and depression have higher depression, impulsivity, and hostility scores and are significantly more likely to make a suicide attempt compared to subjects with depression alone. Depressed subjects with comorbid PTSD tend towards earlier age of first hospitalization and a higher number of hospitalizations compared to depressed individuals without comorbid PTSD. Lower affinity of alpha-2 adrenoreceptors and higher plasma tyrosine availability to the brain are associated with comorbid PTSD and depression, but not with PTSD alone. Individuals with comorbid PTSD and depression do not exhibit the classic rapid eye movement sleep architectural modifications associated with depression, despite the fact that several other psychophysiological indices of dysphoria are detectable in their sleep. In fenfluramine challenge studies, depressed patients with comorbid PTSD have lower plasma cortisol compared to depressed patients without comorbid PTSD. Cortisol levels increase with age and the number of previous major depressive episodes is a predictor of the cortisol response to fenfluramine administration in depressed patients without PTSD, but not in depressed patients with comorbid PTSD. Depressed subjects with comorbid PTSD have higher cerebrospinal fluid homovanillic acid levels compared with depressed subjects without comorbid PTSD. Thus, studies suggest that patients suffering from comorbid PTSD and depression differ clinically and biologically from individuals with PTSD alone or depression alone. It is possible that some or all individuals diagnosed with comorbid PTSD and depression have a separate psychobiological condition that can be termed "post-traumatic mood disorder". Future clinical and neurobiological studies may not only advance our understanding of the role of environmental and genetic factors in the etiology and pathogenesis of stress-related disorders, but also be useful in refining conceptions of stress-related disorders themselves and possible approaches to the treatment of these conditions.