Combat injury, pain, and mental health outcomes in US Army service members

Background The impact of combat injury on the development of chronic pain and mental health concerns in combat-exposed populations is unknown. This study examined associations of combat injury and injury–related pain with pain-related factors and mental health outcomes, and potential mediation of the relation between combat injury and mental health outcomes by pain-related factors. Methods Pain interference, pain catastrophizing, pain intensity, post-traumatic stress disorder (PTSD), and major depressive episode (MDE) were assessed in (1) a probability sample of US Army soldiers and veterans cross-sectionally and (2) US Army soldiers before and 1, 3, and 9 months after deployment to Afghanistan. Associations among these variables were modeled using logistic regression and multiple mediation analyses. Results Among 5003 service members with cross-sectional data, combat injury–related pain was associated with increased odds of clinically significant pain intensity (OR=2.69), pain interference (OR=3.69), MDE (OR=2.17), and PTSD (OR=3.96) relative to pain from other injuries and conditions. Among 4645 service members assessed pre- and post-deployment, combat injury was associated with increased odds of new-onset pain interference (OR=2.78), pain catastrophizing (OR=2.75), PTSD (OR=4.06), and MDE (OR=2.56) 3 months post-deployment, and PTSD (OR=2.86) and MDE (OR=1.74) 9 months post-deployment. Pain-related factors mediated the relations of combat injury with post-deployment PTSD and MDE. Conclusions Combat injury is associated with greater odds of pain interference, pain catastrophizing, PTSD, and MDE compared to other sources of pain in a cohort of US service members. Efforts to address pain-related factors following combat injury may mitigate the risk of subsequent chronic pain and mental health disorders.