Longitudinal Relationship of Combat Exposure With Mental Health Diagnoses in the Military Health System

Abstract

ABSTRACT Introduction Combat deployment is associated with mental and physical health disorders and functional impairment. Mental health (MH) diagnoses such as adjustment and anxiety disorders have received little research attention but may reflect important postdeployment sequelae. The purpose of this study was to investigate the association of combat exposure with the acquisition of a wide range of mental health diagnoses over 2 years. Materials and Methods This retrospective longitudinal study utilized multiple administrative Military Health System datasets compiled for all individuals who entered active duty in the U.S. Army from FY2005 to FY2011. A total eligible cohort of 289,922 Service members was stratified into three mutually exclusive groups according to their deployment status after 2 years in service: Deployed, Combat-Exposed; Deployed, Not-Combat-Exposed; and Not Deployed. Outcomes of interest were new mental health diagnoses grouped into six categories—posttraumatic stress disorder, anxiety, adjustment, mood, substance use disorders, and any MH diagnosis. Survival analyses over 2 years were conducted and adjusted hazard ratios were calculated. Results Combat exposure in the first 2 years of military service was associated with significantly higher rates of a wide range of mental health diagnoses over a two-year follow-up period, compared with deployment with no combat exposure and no deployment. Adjusted cumulative failure proportions demonstrated that approximately a third of the Combat-Exposed group, a quarter of the Not-Combat-Exposed, and a fifth of the Not Deployed groups received a MH diagnosis over 2 years. For all groups, cumulative failure proportions and incidence rates were highest for adjustment disorder and lowest for posttraumatic stress disorder diagnoses. Conclusions Researchers and providers should be alerted to the impact of combat exposure and the wide range of MH conditions and diagnoses that may represent important postdeployment sequelae.