Biological vulnerability factors for the development of PTSD, depressive, and fatigue symptoms in response to military deployment are condition specific

Rationale: Deployed military personnel are at risk for (mental) health problems, including post traumatic stress disorder (PTSD), major depressive disorder (MDD), and fatigue. We hypothesized that development of these conditions is associated with biological vulnerability factors. Therefore, we assessed whether the development of PTSD, depressive and/or fatigue symptoms in response to military deployment could be predicted by glucocorticoid (GC) signalling in leukocytes and the capacity of peripheral blood cells to produce cytokines. Methods: We included 1,032 Dutch military personnel prior to deployment to Afghanistan. Symptom severity was assessed 6 months after return. In blood collected prior to deployment, we assessed GC signalling in leukocytes (glucocorticoid receptor [GR] number, target gene mRNA expression, and GC-sensitivity) and cytokine production upon stimulation with LPS, PHA, or IL-1β. Results: We identified different vulnerability factors for development of a high level of PTSD, depressive, and fatigue symptoms. PTSD symptom development was predicted by high GC signalling in leukocytes. In contrast, depressive symptom development was associated with low GC signalling in T-cells and high T-cell cytokine production capacity. Finally, development of fatigue was associated with low GC signalling in monocytes prior to deployment and high reactivity of monocytes to IL-1β after deployment. Conclusions: The identified vulnerability factors for the development of high levels of PTSD, depressive, and fatigue symptoms were condition specific. This indicates PTSD, depression, and fatigue have different underlying biological mechanisms. Moreover, the results suggest that the biological profile prior to stress/trauma exposure may not only determine if a stress-related condition will develop but also which specific stress-related condition will develop.