Effects of deployment on mental health in modern military forces: a review of longitudinal studies

Background. Earlier studies presenting evidence that operational deployment negatively affects mental health outcomes among military personnel and veterans generally have lacked conclusiveness, largely because of cross-sectional or retrospective design. Purpose. To review longitudinal studies investigating mental health outcomes of military personnel deployed in recent conflicts. Methods. MEDLINE database was searched using relevant keywords and MESH terms. The US Millennium Cohort study website was used to obtain the list of relevant publications. Only prospective longitudinal cohort studies investigating mental health outcomes in deployed post Vietnam era military or veteran populations of developed countries were included. Results. Eighteen studies fulfilled the inclusion criteria. Adverse effects included the increased incidence of post-deployment PTSD and depression. Individuals with the lowest functional scores and those exposed toprevious traumatic assault were particularly vulnerable to a new onset of PTSD after combat exposure. Factors influencing the incidence of post-deployment PTSD included depression symptoms present during deployment, the presence of stress reaction during combat exposure and reception of associated frontline treatment, and the number of negative life events experienced after the traumatic event. More mental health problems were reported in soldiers returning from Iraq on the second screening conducted several months after their return, compared with the first screening immediately upon their return. Some mental health symptoms (anxiety and depression) improved between deployments, while others (PTSD and panic attacks) did not improve. Conclusion. The results indicate that combat exposure, not deployment in general, had an adverse effect on mental health. Mental health indicators in personnel who were deployed but not exposed to combat were often better than those in non-deployed personnel. Health outcomes and health needs were affected both by individual characteristics and post-deployment life events and these changed over time