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Since the beginning of the 1990s, the Danish military has deployed more than 40,000 soldiers to war zones, especially to the Balkans, Iraq, and Afghanistan (Source: The Danish Defense). To the war in Afghanistan alone, the Danish Defense has to date deployed 9,918 unique soldiers with a total of 18,015 deployments (Source: The Danish Defense). The total population of Denmark is 5.66 million, resulting in a relatively high deployed-to-population ratio. Since research in the field have found deployed soldiers to be at increased risk for mental health problems following deployment this large number entails a potential public health problem for the Danish society.

The Research and Knowledge Center in the Danish Veteran Center has over the last years conducted a longitudinal study of Danish soldiers deployed to Afghanistan from February to August 2009 on potential mental health problems that might arise in this population. In the following, a few highlights focusing on the development of posttraumatic stress (PTS) in this sample will be presented, and the relevance and generalizability of these findings to military populations from other countries will be discussed.

A longitudinal study of Danish veterans

From 2009 to 2012, 743 Danish soldiers from the International Security Assistance Force (ISAF) Team 7 participated in a research study aimed at investigating the long-term psychological and social consequences of military deployment. The soldiers were assessed before and during deployment, at return, as well as three months, seven months, and 2.5 years after home coming. All assessments included a wide range of validated self-report questionnaires, and symptoms of PTS were assessed at all time points with the PTSD checklist, Civilian Version (PCL-C (2)). In the following, we present findings on the development of PTS symptoms from before until 2.5 years after deployment.


As seen in Figure 1, more than 85 percent have no or few symptoms of PTS until 3 months after home coming. After the three months assessment, the proportion of soldiers with few or no symptoms decreases, resulting in 72.5 percent of the soldiers having no or few symptoms 2.5 years after home coming.

Correspondingly, the proportion of soldiers with moderate or high level of PTS-symptoms increases, and at the 2.5 years assessment, 9.7 percent of the soldiers has a high level of PTS-symptoms (“High” defined as a PCL-score of ≥ 44, suggested as the best cut off score in this sample by ROC curve analysis (3)).

To gain greater insight in the development of PTS-symptoms over time in this population, we also estimated the latent trajectories of PTS-symptoms from before to 2.5 years after deployment by application of Latent Growth Mixture Modeling (LGMM (4)). We identified six different symptom trajectories (Figure 2). Notably, 78 percent of the sample displayed resilience, in that they belonged to a trajectory of little or no symptomatology across all assessments.

In the other end of the spectrum, two trajectories were characterized by a very high symptom level at the last assessment: one with a pattern of deployment-related symptom-relief followed by drastic worsening (relieved-worsening: 2.0 percent) and one with a pattern of low symptoms through the +3 months assessment, followed by symptom increase (late onset: 5.7 percent). The remaining three trajectories showed varying levels of fluctuating symptomatology. Importantly, all of the soldiers who ended up with very high levels of symptomatology at 2.5 years had very low symptomatology upon return, suggesting that the most vulnerable individuals cannot be identified at the return assessment by looking solely at PTS symptomatology.

Why should other countries care? Comparability and relevance of Danish military samples

One question that arises when comparing military samples across different nations is the comparability of mission experience, especially combat exposure. We compared the combat exposure of the Danish soldiers in our sample to combat exposure among American and British soldiers. Generally similar levels of combat exposure were found: in a study of British soldiers (5) 48.3 percent of those who deployed to Afghanistan reported to have to have seen someone from the unit getting injured or killed, while this was the case for 57.3 percent of our sample. Also, 87.7 percent of our sample reported to have been under fire from the enemy, while 75.8 percent of the British sample reported to have been under small arms, artillery, rocket, or mortar fire.

Similarly, in a study of American soldiers, 66 percent of those deployed to Afghanistan reported being shot at and 84 percent reported having experienced artillery, rocket, or mortar fire. Hence, we believe that the level of combat exposure is largely comparable for Danish, American, and British soldiers deployed to Afghanistan.

Upon return from deployment, Danish soldiers are settling back into life in a society that is very different from e.g. the American society. One important difference is the health care system, which in Denmark is public, tax-funded, and provides 100 percent coverage for everyone. Due to this and other differences, direct comparisons of home coming characteristics between Danish soldiers and soldiers from other nations should be done cautiously.

However, one characteristic of the Danish health care system is also the feature that makes it unique in terms of possible research avenues: In Denmark, central registries hold information on hospitalizations, psychiatric and somatic diagnoses, use of psychopharmacological medication, labor market connection and a host of other relevant mental health outcomes and correlates. Information is stored for all citizens and saved under a civil registration number that enables in merging of registries and databases at the individual level. Additionally, it is possible to retrieve information not only for the individual soldier, but also for his or her family members. Hence, longitudinal studies that do not rely on retrospective self reports can be conducted in for example military samples.

Over the next years, The Research and Knowledge Center in the Danish Veteran Center will aim to increase knowledge on the outcomes of military deployment by incorporating these registries in the above described study as well as other studies to provide objective information on long-term mental- and physical health, functioning and labor market connection. This will be extended to also include the impact of military deployment on the family; i.e. health and social function of children, partners and wives of military personnel.

Further, we will include neonatal blood samples from the soldiers, which are available from The Danish Neonatal Screening Biobank for everyone born in 1982 or later. This will enable us to study if and how genetics are related post-deployment mental health in Danish soldiers. Thus, we expect to contribute to the knowledge not only on Danish veterans, but on general mechanisms and characteristics of deployment consequences that are cross-cultural of nature.

About the Authors

Karen-Inge Karstoft, PhD, finished her doctoral thesis in the spring of 2014 which focused on individual differences in the development of resilience or posttraumatic stress reactions following military deployment. She is currently a researcher at The Research and Knowledge Center in the Danish Veteran Center, and continues this line of research with a primary focus on genetic and epigenetic mechanisms that are involved in flagging vulnerability for posttraumatic stress following deployment.

Anni B. S. Nielsen, PhD, MA, RN, is researcher at The Research and Knowledge Center in the Danish Veteran Center. Her research experience includes longitudinal cohort-studies of self-rated health and other health related outcomes in different populations with e.g. inclusion of data from national registries. Her current research focuses on symptoms of bodily distress syndrome among veterans as well as health and social function of children, partners and wives of military personnel. 

Søren B. Andersen, PhD, is head of The Research and Knowledge Center in the Danish Veteran Center. To date, his research has focused on the biological basis of behavior, emotions and personality. He was previously appointed as a lecturer at Swansea University and is a board member of the Society of Applied Neuroscience. His current research focuses on genetic, epigenetic, electrophysiological, and psychological risk factors for the development of PTSD following deployment. 


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