Substance Use Disorders and Timing of Warrior Transition Unit Assignment Increase Likelihood of Military Discharge after Post-Deployment Rehabilitation in Army Warrior Transition Units

Background: Military discharge after combat deployment is associated with physical injury, behavioral health, and reintegration difficulties. In Warrior Transition Units (WTUs), soldiers receive rehabilitative care to facilitate returning to duty or transitioning to veteran status. Although most soldiers return to duty after WTU assignment, sparse evidence exists on WTU attrition. We investigated factors associated with discharge after WTU assignment.

Methods: Retrospective cohort study analyzed U. S. Department of Defense Military Health System data to examine factors associated with discharge after WTU assignment in Army service members (N=31,094) who returned from deployments, FY2008-2015. Military discharge was defined as separation within 180 days after the first WTU assignment end date. WTU index deployment was the deployment preceding WTU assignment. Timing of WTU assignment defined after WTU index deployment end date (post-deployment) was categorized: <30 days before deployment end date, 31-90 days post-deployment, 91-180 days post-deployment, 181-365 days post-deployment, >365 days post-deployment. Primary physical and behavioral health diagnoses flags defined using ICD-9 codes were measured <30 days after WTU assignment begin date included: amputations, spinal, shrapnel, burns, blindness, pain, sleep, musculoskeletal, traumatic brain injuries; adjustment, mood, posttraumatic stress disorder (PTSD), anxiety; alcohol (AUD), drug (DUD), and opioid use (OUD) disorders, psychosocial problems, suicide, overdose. Two logistic regressions (with/without interactions) controlled for sociodemographics (age, sex, race, marital status, single parent), military (service component, rank, TRICARE coverage), deployment (deployment frequency, total time deployed, index deployment length), WTU (timing of WTU assignment, WTU assignment frequency), physical and behavioral health diagnoses. Interactions included: service component*timing of WTU assignment, service component*acute pain, service component*chronic pain. Subgroup analyses were stratified by timing of WTU assignment.

Results: Service component moderated associations between timing of WTU assignment and discharge. Odds ratios (OR) and 95% confidence interval (CI) estimates indicated National Guard (91-180 days post-deployment; OR: 1.40 (1.04-1.88); >365 days post-deployment; OR: 1.74 (1.41-2.16)] and Reservists [91-180 days post-deployment, OR: 1.80 (1.27-2.56); 181-365 days post-deployment; OR: 1.59 (1.08-2.32); >365 days post-deployment; OR: 1.58 (1.21-2.05)] had increased odds of discharge than Active duty. Primary PTSD diagnoses decreased odds [OR: 0.53 (0.47, 0.60)], whereas suicide [OR: 2.34 (1.47-3.72)], overdose [OR: 2.16 (1.24-3.77)] and OUD [OR: 1.53 (1.03-2.28)] increased odds of discharge. Subgroup analyses revealed differential physical and behavioral health associations by timing of WTU assignment. Primary substance use disorder (SUDs) diagnoses increased odds of discharge, including AUD [before deployment ended, OR: 1.95 (95% CI: 1.23-3.09); 91-180 days post-deployment, OR: 1.97, (95% CI; 1.03-3.77)]; DUD [<30 days post-deployment, OR: 1.63 (95% CI: 1.09-2.46)]; OUD [>365 days post-deployment, OR: 1.89, (95% CI: 1.07-3.31)].

Conclusions: SUDs, suicide, overdose, and timing of WTU assignment increased odds of discharge after WTU assignment in soldiers redeployed, FY2008-2015. Suicide or overdose attempts more than doubled odds of discharge. Military social workers can promote social change through targeted suicide, overdose, and SUD prevention, and timely mental health and SUD treatment referrals to reduce attrition after WTU assignment. Identifying preventable conditions increasing WTU attrition can inform post-deployment health policy and clinical decision-making to retain soldiers in military service after post-deployment rehabilitation and recovery.