Time-varying associations of suicide with deployments, mental health conditions, and stressful life events among current and former US military personnel: a retrospective multivariate analysis

Background US military suicides have increased substantially over the past decade and currently account for almost 20% of all military deaths. We investigated the associations of a comprehensive set of time-varying risk factors with suicides among current and former military service members. Methods We did a retrospective multivariate analysis of all US military personnel between 2001 and 2011 (n= 110 035 573 person-quarter-years, representing 3 795 823 service members). Outcome was death by suicide, either during service or post-separation. We used Cox proportional hazard models at the person-quarter level to examine associations of deployment, mental disorders, history of unlawful activity, stressful life events, and other demographic and service factors with death by suicide. Findings The strongest predictors of death by suicide were current and past diagnoses of self-inflicted injuries, major depression, bipolar disorder, substance use disorder, and other mental health conditions (compared with service members with no history of diagnoses, the hazard ratio [HR] ranged from 1.4 [95% CI 1.14-1.72] to 8.34 [6.71-10.37]). Compared with service members who were never deployed, hazard rates of suicide (which represent the probability of death by suicide in a specifi c quarter given that the individual was alive in the previous quarter) were lower among the currently deployed (HR 0.50, 95% CI 0.40-0.61) but signifi cantly higher in the quarters following fi rst deployment (HR 1.51 [1.17-1.96] if deployed in the previous three quarters; 1.14 [1.06-1.23] if deployed four or more quarters ago). The hazard rate of suicide increased within the fi rst year of separation from the military (HR 2.49, 95% CI 2.12-2.91), and remained high for those who had separated from the military 6 or more years ago (HR 1.63, 1.45-1.82). Interpretation The increased hazard rate of death by suicide for military personnel varies by time since exposure to deployment, mental health diagnoses, and other stressful life events. Continued monitoring is especially needed for these high-risk individuals. Additional information should be gathered to address the persistently raised risk of suicide among service members after separation.