Mediation and Moderation of the Relationship Between Combat Experiences and Post-Traumatic Stress Symptoms in Active Duty Military Personnel

Background: Post-traumatic stress disorder (PTSD) is a major health concern among the U.S. military population, affecting up to 12% to 24% of veterans returning from Iraq and Afghanistan. Sleep disturbances, neuroticism, and childhood trauma have all been associated with the development of PTSD in military populations, especially in relation to combat experiences. The effects of disrupted sleep and post-traumatic stress can affect the physical well-being of soldier and sailors in the field and impact them for years after deployment. This study aimed to evaluate the relationship between self-reported measures of combat experiences, PTSD symptoms, sleep, neuroticism, and childhood adversity in an active duty military population. Methods: 972 U.S. Navy Sailors serving in Afghanistan were given anonymous surveys that assess scales of combat stressors, PTSD symptoms, sleep problems, neuroticism, adverse child experiences (ACEs), and other covariates. Sleep disturbances were hypothesized as moderators, having an indirect effect on the relationship between combat experiences and PTSD symptoms. Neuroticism scores and ACEs were proposed as moderators of the combat-PTSD symptom relationship. Mediation and moderation models were developed and tested using logistic regressions. Findings: Increased number of combat experiences was found to be a significant predictor of PTSD, even when adjusting for all covariates (p < 0.05). Consistent with partial mediation, nightmares had an indirect effect on the relationship between combat experiences and PTSD symptoms in the final model (path coefficient = 0.233, 95% confidence interval = 0.036, 0.483). Neuroticism was an independent predictor of PTSD symptoms (p < 0.001), but the interaction of combat and neuroticism did not predict symptoms of PTSD. ACEs did not have a significant impact in the model as either an independent predictor or a moderating factor. Discussion: These results indicate that the presence of nightmares may partially explain how traumatic combat experiences lead to the development of PTSD. The study also reaffirms neuroticism as risk factor for developing PTSD symptoms. These findings highlight the importance of sleep hygiene and operational stress models in combat situations and may help stress control professionals address risk factors associated with PTSD symptoms.