Event-related Factors, Altruism, and Substance Use in Traumatization of Hurricane Student Volunteers: A Bayesian Model for the Follow-up Running Head: Bayesian Analysis of Disaster Traumatization

In surging disaster research, trauma psychologists called for more longitudinal investigation on factors related to resilience/lower traumatization for populations exposed to collective trauma. Little research has employed a Bayesian approach, a means with advantages in small samples and dichotomized endpoints. The present study addressed these needs with a two-wave survey on hurricane volunteers to demonstrate pathways to traumatization after deadly disasters. A survey was conducted at three months (Wave-1) and six months (Wave-2) after hurricane Katrina and Rita (H-KR) (N=201). Standardized instruments were used to assess posttraumatic stress symptoms (PTSS) altruism, substance use for coping, and event-related factors in Wave-1 and posttraumatic stress disorder (PTSD) in Wave-2. Bayesian structural equation modeling (Bayesian-SEM) was performed to evaluate the role of altruism and using substances to cope with Wave-2 PTSD. Traumatization was identified in 18% of participants, showing a significant increase in Wave-1 and a 12% decrease, albeit non-significant, in Wave-2. Supported by all Model fit indices, the final solution of Bayesian-SEM showed no direct overtime effect of altruism and substance use, but the indirect effects through the enhancing role of Waves-1 PTSS, on Wave-2 PTSD. Contrary to cross-sectional studies, no protection from peritraumatic positive emotions was observed. These findings emphasize the importance of longitudinal post-disaster research. Given the new evidence on volunteers' traumatization, altruism, and substance use during times of crisis with limited resources, further investigation among volunteers is crucial. The absence of identified protective factors in volunteers raises concerns for future implications in trauma psychology theory, research, and practice.