Elevated rates of adverse PTSD symptom trajectories in a civilian mass-trauma cohort

Background: Civilian mass-trauma events can produce heterogeneous outcomes, ranging from resilience to adverse symptom trajectories that may develop into chronic posttraumatic stress disorder (PTSD). Key factors associated with adverse PTSD symptom trajectories include female sex, childhood adversity, and sleep disturbances. Objectives: To characterize PTSD symptom trajectories in a large civilian cohort during the first year following the 7 October 2023 Nova music-festival mass-trauma event. Method: 392 survivors completed the PTSD Checklist for DSM-5 (PCL-5) at T1 (1–5 months post-event) and T2 (8–12 months post-event). Symptom trajectories were classified using k-means clustering with three standardized features: intercept, rate of change, and time since the event. Within-class changes over time were tested with paired t-tests. Multinomial logistic regression examined associations with pre-specified factors with 10-fold cross-validation and false-discovery-rate (FDR) correction. Results: Among survivors, four symptom classes emerged: Resilient (25.3%), Partially Improved (20.2%), Consistently High (28.8%), and Worsening (25.8%). Overall, 54.6% of survivors exhibited adverse symptom trajectories (Consistently High or Worsening) one year following trauma. Female sex, childhood adversity, and post-trauma sleep disturbances were each associated with lower odds of Resilient class membership. Conclusions: Adverse PTSD symptom trajectories were unusually high one year following a civilian mass-trauma event, indicating a sustained mental-health burden among survivors. These findings support extended follow-up and may help inform future research on intervention strategies in civilians exposed to complex and prolonged trauma.