Trajectories of depression symptoms from pre- to post- deployment: Does previous trauma predict symptom increase?

•We estimate heterogeneous trajectories of depression symptoms from pre- to 6.5 years post-deployment in 530 Danish soldiers.•In total, 9.4% experience a dramatic symptom increase from before through 6.5 years after deployment.•Course of depression following deployment is differentially predicted by rank, childhood and adult life trauma, neuroticism, and early post-deployment PTSD-symptoms. A significant minority of individuals experience depression following military deployment. The course of depression symptoms varies over time and across individuals; several factors including combat exposure influence depressions incidence and course. Importantly, previous trauma, especially in childhood, have been found increase the risk of post-deployment depression. In a prospective sample of 530 soldiers deployed to Afghanistan in 2009, we used latent growth mixture modeling (LGMM) to estimate trajectories of depression symptoms from before through 6.5 years after deployment. In a multinomial logistic regression model, we tested if childhood and adult life trauma predicted trajectory membership in combination with combat exposure and neuroticism. We identified a large trajectory of few depression symptoms from before through 6.5 years after deployment (Low-stable, 86.5%), a trajectory with somewhat elevated symptoms (Medium-fluctuating, 4.0%), and a trajectory with few symptoms before deployment and a steep increase to a severe symptom level 6.5 years after deployment (Low-increasing, 9.4%). The Low-increasing trajectory was predicted by lower rank and childhood trauma, while the Medium-fluctuating trajectory was predicted by neuroticism, adult life trauma, and post-deployment PTSD symptoms. Attrition and use of self-report measures for depression and trauma. Depression symptoms follow a heterogeneous course from before through 6.5 years after deployment with 9.4% experiencing symptom increase, resulting in severe symptoms 6.5 years after deployment. Trajectories are differentially predicted by rank, childhood and adult life trauma as well as neuroticism and PTSD symptoms, illustrating the clinical importance of taking individual differences of symptom course into account.