Dr. Alieke Reijnen
Samenvatting van het proefschrift
This thesis has focused on results from a large prospective longitudinal cohort study in Dutch military personnel (PRISMO: Prospective Research in Stress-related Military Operations). In the current study, military personnel (N=1007) were assessed before and up to 5 years after a 4-month deployment to Afghanistan. The goal was to investigate psychological and biological aspects of stress-related (mental) health problems to be able to better predict who is at risk for the development of symptoms after deployment to a combat zone. The first aim was to gain more insight in the impact of deployment to a combat zone on the development of mental health problems, more specifically Posttraumatic Stress Disorder (PTSD), and character traits. It was shown that, despite the exposure to high intensity combat, a large percentage of Dutch military personnel does not develop mental health problems or show changes in character after deployment to Afghanistan. However, there is a group of individuals that reports significant difficulties with adaptation to life in the Netherlands. Compared to pre-deployment rates, the prevalence estimates of mental health problems (symptoms of fatigue, PTSD, hostility, depression, and anxiety) were found to increase after deployment. The course of this development appeared to be specific for various mental health problems. Moreover, whereas in some individuals, symptoms of PTSD emerged immediately and decreased after a year, in others these symptoms were only first reported as late as 5 years after deployment. In addition, whereas the level of the character trait cooperativeness was stable over time, self-directedness decreased over 5 years post-deployment. This decline in self-directedness was associated with the development of PTSD symptoms. Although many participants report exposure to combat-related stressors, only a subset develops mental health problems. Therefore, the second aim was to look if potential stress-related biological risk or protective factors (so called biomarkers) correlated to the development of symptoms of PTSD over time in military men. To do so, testosterone, neuropeptide-Y (NPY), oxytocin (OT), and arginine vasopressin (AVP) levels were measured in plasma before and at 1 and 6 months post-deployment. The findings demonstrated that whereas low plasma testosterone levels prior to deployment might represent a risk factor, the peripherally measured neuropeptides NPY, OT and AVP currently do not qualify as useful susceptibility biomarkers for the development of PTSD symptoms in military men after combat. The increase in symptoms even years after deployment underlines the importance of studying whether military personnel can be warned. Although many potentially interesting risk factors are identified, it is currently not possible to reliably predict an individuals’ risk of developing PTSD after exposure to a traumatic event. However, the use of complex and advanced statistical methods in large prospective longitudinal studies, such as PRISMO, to address the heterogeneity of PTSD and to identify multifactorial models are promising in the development of risk prediction tools and personalized preventive interventions.