Delayed onset of depressive symptoms in deployed Dutch military personnel: Identifying distinct psychological, biochemical, and genetic pre-deployment profiles

Background: Depression is common in the military, with research highlighting variability in depressive symptom development after deployment. This report builds on previous findings to explore differences in pre-deployment psychological, biochemical, and genetic variables across distinct depressive symptom trajectories, with a particular focus on the delayed-onset-increasing trajectory. Methods: A sample of 846 military personnel deployed to Afghanistan (2005–2008) was categorized into resilient (66 %, n = 558), intermediate-stable (20 %, n = 173), symptomatic-chronic (9 %, n = 74), and delayed-onset-increasing (5 %, n = 41) trajectories from pre- to 10 years post-deployment. Differences in pre-deployment characteristics (e.g., psychological, biochemical, and genetic) among the depression trajectories were examined using a non-parametric multivariate analysis. Results: Individuals in the delayed-onset-increasing trajectory had higher general mental health symptom scores than those in the resilient trajectory, but lower scores on fatigue, burnout, and personality factors than the symptomatic-chronic trajectory. No differences were found between the delayed-onset-increasing and the intermediate-stable trajectory. The symptomatic-chronic and resilient trajectories showed significant different scores across most pre-deployment psychological characteristics compared to the other trajectories. For the biochemical and genetic variables no significant differences were found. Conclusions: Our study found that pre-deployment characteristics do not distinguish the delayed-onset-increasing trajectory from the intermediate-stable trajectory, with differences emerging post-deployment likely due to negative life events. Individuals vulnerable in one aspect of mental health may be at risk across multiple psychological domains, highlighting the need to focus on a broader range of symptoms to support vulnerable military personnel and enhance resilience.