The article is dedicated to the psychological structuring of institutional trust and psychological risk management in international security and defense-related operations, with an empirical anchoring in Eastern Africa. Relevance stems from the persistence of high-insecurity environments where cooperation with security institutions is filtered through threat appraisal, trauma-related cognitive shifts, and occupational mental health constraints among personnel. Scientific novelty is articulated through an integrated multilevel model that links civilian trust calibration to officer psychological vulnerability and to organizational mediation mechanisms, rather than treating legitimacy as a purely administrative variable. The work describes how contingent trust emerges through localized interaction patterns and communication buffers, and it studied how depression, suicidality, substance-related coping, and resilience-related protective resources co-produce institutional credibility. Special attention is paid to the recursive loop in which civilian mistrust amplifies officer stress, and stress-driven behavioral dysregulation further corrodes public confidence. The aim of the study is to identify psychologically grounded leverage points for stabilizing institutional trust in high-risk security environments. Comparative synthesis, structured source analysis, and analytical modeling are used to solve it. The conclusion outlines actionable psychosocial entry points for security governance design. The article will be useful for policymakers, mission planners, and security-sector training units.