Longitudinal Patterns of Distress and Resilience in Japan Self-Defense Forces Peacekeepers

The mission demands and the local environment associated with the United Nations peacekeeping operations (PKO) are psychologically stressful. This study aimed to identify longitudinal trajectories of psychological distress associated with PKO deployment and examine the influence of pre-deployment resilience. Additionally, we investigated the associations of post-deployment job stressors and support factors with the psychological distress trajectories.

A prospective cohort study was conducted among the Japan Ground Self-Defense Forces personnel deployed to the United Nations Mission in the Republic of South Sudan between November 2015 and May 2017 in 6-month deployment rotations. Data was collected from pre-deployment to up to 24 months post-deployment. Psychological distress was measured using the Kessler Psychological Distress Scale, and latent growth mixture modeling (LGMM) identified distinct trajectories. We also examined the associations of pre-deployment resilience, assessed by the Tachikawa Resilience Scale, and general mental health, assessed by the 30-item General Health Questionnaire, with post-deployment job stressors and support factors, assessed by the Brief Job Stress Questionnaire. This study was approved by the institutional review board of the National Defense Medical College.

Latent growth mixture modeling identified 4 trajectories: Resilient (57.9%), Recovery (18.6%), Chronic (13.0%), and Delayed (10.5%). Multinomial logistic regression revealed officer rank, pre-deployment sleep disturbance, and anxiety and dysphoria as risk factors among the Chronic group, while resilience, especially cognitive flexibility, was a protective factor. At 12 months post-deployment, quantitative and qualitative job overloads were risk factors among Chronic and Delayed groups, respectively, and supervisor support was a protective factor among the Chronic group.

Approximately one-fourth of the personnel experienced long-term psychological distress. Higher levels of pre-deployment resilience with cognitive flexibility, good sleep quality, and stable mood might play key protective roles. Post-deployment job stressors and support factors were also associated with psychological outcomes, highlighting the importance of strengthening post-deployment support systems along with pre-deployment interventions to enhance resilience, improve sleep, and stabilize mood to promote mental health among PKO personnel.