First responders to disasters are at risk of developing post-traumatic stress disorder (PTSD). The trajectories of post-traumatic stress symptom severity differ among individuals, even if they are exposed to similar events. These trajectories have not yet been reported in non-Western first responders.

We aimed to explore post-traumatic stress symptom severity trajectories and their risk factors in first responders to the 2011 Great East Japan Earthquake (GEJE) – a historically large earthquake that resulted in a tsunami and a nuclear disaster.

A total of 55 632 Japan Ground Self-Defense Force (JGSDF) personnel dispatched to the GEJE were enrolled in this 7-year longitudinal cohort study. PTSD symptom severity was measured using the Impact of Event Scale-Revised. Trajectories were identified using latent growth mixture models (LGMM). Nine potential risk factors for the symptom severity trajectories were analysed using multinomial logistic regression.

Five symptom severity trajectories were identified: ‘resilient’ (54.8%), ‘recovery’ (24.6%), ‘incomplete recovery’ (10.7%), ‘late-onset’ (5.7%), and ‘chronic’ (4.3%). The main risk factors for the four non-resilient trajectories were older age, personal disaster experiences and working conditions. These working conditions included duties involving body recovery or radiation exposure risk, longer deployment length, later or no post-deployment leave and longer post-deployment overtime.

The majority of first responders to GEJE were resilient and developed few or no PTSD symptoms. A substantial minority experienced late-onset and chronic symptom severity trajectories. The identified risk factors can inform policies for prevention, early detection and intervention in individuals at risk of developing symptomatic trajectories.

The 2011 Fukushima Daiichi nuclear accident was the worst nuclear disaster since Chernobyl. The Daiichi workers faced multiple stressors (workplace trauma, victim experiences, and public criticism deriving from their company’s post-disaster management). Literatures suggest the importance of workplace interpersonal support (WIS) in enhancing psychological health among disaster workers. We sought to elucidate the role of their demographics, disaster-related experiences, and post-traumatic stress symptoms on perceived WIS.

We analyzed self-report questionnaires of 885 workers 2-3 months post-disaster. We used sociodemographic and disaster exposure-related variables and post-traumatic stress symptoms (measured by the Impact of Event Scale-Revised) as independent variables. We asked whether WIS from colleagues, supervisors, or subordinates was perceived as helpful, and used yes or no responses as a dependent variable. Logistic regression analyses were performed to assess correlates of WIS.

Of the participants, one-third (34.7%) reported WIS. WIS was associated with younger age (20-28 years [vs 49-], adjusted odds ratio [aOR]: 3.25, 95% CI: 1.99-5.32), supervisory work status (aOR: 2.30, 95% CI: 1.35-3.92), and discrimination or slur experience (aOR: 1.65, 95% CI: 1.08-2.53).

Educational programs focusing on WIS might be beneficial to promote psychological well-being among nuclear disaster workers, especially younger workers, supervisors, and workers with discrimination experiences. (Disaster Med Public Health Preparedness. 2018;12:460–463)