Early prediction of mental health problems following military deployment: Integrating pre- and post-deployment factors in neural network models.

Military personnel deployed to war zones are at increased risk of mental health problems such as posttraumatic stress disorder (PTSD) or depression. Early pre- or post-deployment identification of those at highest risk of such problems is crucial to target intervention to those in need. However, sufficiently accurate models predicting objectively assessed mental health outcomes have not been put forward. In a sample consisting of all Danish military personnel who deployed to war zones for the first (N = 27,594), second (N = 11,083) and third (N = 5,161) time between 1992 and 2013, we apply neural networks to predict psychiatric diagnoses or use of psychotropic medicine in the years following deployment. Models are based on pre-deployment registry data alone or on pre-deployment registry data in combination with post-deployment questionnaire data on deployment experiences or early post-deployment reactions. Further, we identified the most central predictors of importance for the first, second, and third deployment. Models based on pre-deployment registry data alone had lower accuracy (AUCs ranging from 0.61 (third deployment) to 0.67 (first deployment)) than models including pre- and post-deployment data (AUCs ranging from 0.70 (third deployment) to 0.74 (first deployment)). Age at deployment, deployment year and previous physical trauma were important across deployments. Post-deployment predictors varied across deployments but included deployment exposures as well as early post-deployment symptoms. The results suggest that neural network models combining pre- and early post-deployment data can be utilized for screening tools that identify individuals at risk of severe mental health problems in the years following military deployment.

Combat Exposure and Risk of Suicide Attempt Among Danish Army Military Personnel.

Objective: The aim of this study was to estimate the association between self-reported perceived danger during deployment, measured as combat exposure or witnessing the consequences of war, and post-deployment suicide attempts among military personnel. Furthermore, the effect of post-deployment symptoms of posttraumatic stress disorder (PTSD) and/or depression on the risk of suicide attempts was also evaluated.Methods: This observational cohort study included Danish Army military personnel who returned from deployment in international missions from 1998 to 2016 and had completed a post-deployment questionnaire. Perceived exposure to danger was ascertained by self-report. Data on suicide attempt were retrieved from national registers. Adjusted Cox regression analyses were used to evaluate if military personnel indicating high level of combat exposure were more likely to have attempted suicides post-deployment than military personnel with lower levels of combat exposure.Results: Eighty-three suicide attempts were registered after homecoming among 12,218 military personnel. Perceived higher exposure to combat was associated with the risk of suicide attempt (hazard ratio = 1.08; 95% CI, 1.01-1.16). Furthermore, the association between combat exposure and suicide attempt was fully mediated by post-deployment symptoms of PTSD and/or depression. No association was found between witnessing consequences of war and the risk of post-deployment suicide attempt.Conclusions: This nationwide study found that combat exposure was associated with an increased risk of suicide attempt among military personnel. This association was, however, fully mediated by mental disorders (PTSD and/or depression). These findings suggest that better psychological follow-up of military personnel identified as having PTSD and/or depression may be warranted.

Forecasting military mental health in a complete sample of Danish military personnel deployed between 1992-2013.

OBJECTIVE: Mental health problems (MHP) are a relatively common consequence of deployment to war zones. Early identification of those at risk of post-deployment MHP would improve prevention efforts. However, screening instruments based on linear models have not been successful. Machine learning (ML) has shown promise for providing the methodological frame for better prognostic models. METHODS: The study population was all Danish military personnel deployed for the first time between January 1, 1992 and December 31, 2013. From extensive registry data, 21 pre- or at-deployment predictors comprising early adversity, social, clinical and demographic variables were used to predict psychiatric contacts (psychiatric diagnosis and/or use of psychotropic medicine) occurring within 6.5 years after homecoming. Four supervised ML methods (penalized logistic regression, random forests, support vector machines and gradient boosting machines) were compared in ability to classify those with high risk of post-deployment MHP and those without. RESULTS: Of 27594 subjects, 2175 (8%) had a psychiatric contact. All four ML methods applied had performances well above chance (Area under the Receiver-operating Curve 0.62-0.68). Positive predictive value for the best model was 0.16. A range of pre-deployment factors were found to be predictive of post-deployment psychiatric contacts. CONCLUSIONS: ML methods can be useful in early identification of soldiers with high risk of MPH in the years following their first deployment. However, performances were modest and positive predictive values were low, limiting the applicability of the models for pre-deployment screening. Future studies should include neurobiological data and deployment experiences to increase accuracy of the models.

Effect of Predeployment Psychiatric Diagnoses on Postdeployment Long-Term Sickness Absence and Mental Health Problems Among Danish Military Personnel.

Military personnel may withhold information on mental health problems (MHPs) for fear of not being permitted to deploy. Past or current MHPs may, however, increase the risk of postdeployment MHPs. Using psychiatric diagnoses rather than self-report assessments in predeployment screening may be a more effective screening strategy for determining deployment fitness. This retrospective follow-up study investigated (a) the extent to which predeployment childhood and adult psychiatric diagnoses predicted postdeployment MHPs, measured as psychiatric diagnosis and the purchase of psychiatric drugs, and long-term sickness absence among formerly deployed Danish military personnel and (b) whether perceived combat exposure moderated or mediated the effect of predeployment psychiatric diagnoses. Complete data were available for 7,514 Danish military personnel who answered questions on perceived combat exposure between 6-8 months after returning from their first deployment to the Balkans, Iraq, or Afghanistan. Data on all psychiatric diagnoses given at Danish hospitals, all medicine purchases, and all sickness absences were retrieved from nationwide research registers. Personnel with predeployment psychiatric diagnoses had a statistically significant higher risk for both postdeployment long-term sickness absence, hazard ratio (HR) = 2.06, 95% CI [1.52, 2.80]; and postdeployment MHPs, HR = 2.38, 95% CI [1.73, 3.27], than personnel without a predeployment psychiatric diagnosis. Personnel with a predeployment psychiatric diagnosis demonstrated a higher risk of reporting high levels of perceived combat exposure. Perceived combat exposure was not found to moderate or mediate the effect of a predeployment psychiatric diagnosis on the two outcomes. Additional findings, limitations, and implications are discussed.

Cognitive ability and risk of post-traumatic stress disorder after military deployment: an observational cohort study.

BACKGROUND: Studies of the association between pre-deployment cognitive ability and post-deployment post-traumatic stress disorder (PTSD) have shown mixed results. AIMS: To study the influence of pre-deployment cognitive ability on PTSD symptoms 6-8 months post-deployment in a large population while controlling for pre-deployment education and deployment-related variables. METHOD: Study linking prospective pre-deployment conscription board data with post-deployment self-reported data in 9695 Danish Army personnel deployed to different war zones in 1997-2013. The association between pre-deployment cognitive ability and post-deployment PTSD was investigated using repeated-measure logistic regression models. Two models with cognitive ability score as the main exposure variable were created (model 1 and model 2). Model 1 was only adjusted for pre-deployment variables, while model 2 was adjusted for both pre-deployment and deployment-related variables. RESULTS: When including only variables recorded pre-deployment (cognitive ability score and educational level) and gender (model 1), all variables predicted post-deployment PTSD. When deployment-related variables were added (model 2), this was no longer the case for cognitive ability score. However, when educational level was removed from the model adjusted for deployment-related variables, the association between cognitive ability and post-deployment PTSD became significant. CONCLUSIONS: Pre-deployment lower cognitive ability did not predict post-deployment PTSD independently of educational level after adjustment for deployment-related variables. DECLARATION OF INTEREST: None. COPYRIGHT AND USAGE: © The Royal College of Psychiatrists 2017. This is an open access article distributed under the terms of the Creative Commons Non-Commercial, No Derivatives (CC BY-NC-ND) license.

A suspected case of systemic envenomation syndrome in a soldier returning from Iraq: implications for Special Forces Operations.

Upon returning to Denmark from a mission in Baghdad, Iraq, under Operation Iraqi Freedom, a 45-year-old Danish Special Forces soldier experienced serious and unexplainable symptoms after being stung by an arthropod. The soldier sought medical attention in an emergency department at a public hospital, where he was diagnosed with an allergic reaction to a wasp, bee, or mosquito sting, animals that are commonly found in Denmark. After a short period of observation, he was prescribed antihistamines and discharged. Within a few hours, the soldier developed severe symptoms consistent with a systemic envenomation. There is no proof of the existence of poisonous animals in Denmark that can cause such symptoms. On the basis of circumstantial evidence, an accidental importation of a venomous spider or scorpion by Danish Special Forces personnel might be the possible cause.