Is there a biological difference between trauma-related depression and PTSD? DST says ‘NO’

Abstract

The use of the low-dose dexamethasone suppression test (DST) as a potentially discriminative marker between post-traumatic stress disorder (PTSD) and depression is still under discussion. In order to compare the influence of these psychopathologies on the DST results, we examined suppression in war-traumatized subjects with one or both of these disorders, as well as in healthy controls. Based on our previous findings, we hypothesized that subjects with any disorder would exhibit higher dexamethasone suppression than healthy controls due to traumatic experiences. This study was a part of a broader project in which simultaneous psychological and biological investigations were carried out in hospital conditions on 399 male participants: 57 with PTSD, 28 with depression, 76 with PTSD+depression, and 238 healthy controls. Cortisol was measured in blood samples taken at 0900 h before and after administering 0.5mg of dexamethasone (at 2300 h). Group means ± standard deviation of cortisol suppression were: 79.4±18.5 in the PTSD group, 80.8±11.6 in the depression group, 77.5±24.6 in the group with PTSD+depression, and 66.8±34.6 in healthy controls. The first three groups suppressed significantly more than the fourth. When the number of traumas was introduced as a covariate, the differences disappeared. The hypothesis was confirmed: in respect to DST, the examined trauma-related psychopathologies showed the same pattern: hypersuppression, due to multiple traumatic experiences.