Impacts of Traumatic Brain Injury and Severe Limb Injury on Death by Suicide: Concurrent Investigations Using Path Analysis

Objective: Utilize path analysis to examine the concurrent associations of traumatic brain injury (TBI) and severe limb injury (SLI) with death by suicide mediated by psychological health (PH) conditions and substance use disorders (SUDs). Setting: Archival career and medical data were obtained from the Career History Archival Medical and Personnel System, the Expeditionary Medical Encounter Database, and the Defense Suicide Prevention Office Suicide Data Repository. Participants: Service members of the air force, army, marines corps, and navy who served more than 30 consecutive days between September 11, 2001, and September 30, 2016. Design: This retrospective cohort study utilized path analysis to examine associations among TBI, SLI, PH conditions, SUD, and death by suicide. Stratification by TBI was tested. Main Measures: Concurrent associations of 2 focal predictors, TBI and SLI, with death by suicide were investigated, mediated by PH conditions (ie, posttraumatic stress disorder, depression, or anxiety disorder), and SUDs (ie, alcohol use disorder or other drug use disorder), adjusting for age, sex, race/ethnicity, service branch, and officer status. Results: In preliminary analyses, TBI, SLI, PH conditions, and SUD were all independently associated with death by suicide. In the first path model, neither of the direct effect of SLI or TBI on death by suicide were significant. TBI shared a stronger association with PH conditions and SUD than SLI did; the association between SLI and SUD was negative. When stratified by TBI status, the association between SUD and death by suicide was stronger among those without (vs with) TBI. Conclusions: Findings suggest complex and nuanced associations between TBI, SLI, PH conditions, SUD, and death by suicide, and underscore the importance of integrated and holistic treatment of injured military service members.