Predicting Post-Disaster Post-Traumatic Stress Disorder Symptom Trajectories: The Role of Pre-Disaster Traumatic Experiences.

The mental health impact of disasters is substantial, with 30-40% of direct disaster victims developing post-traumatic stress disorder (PTSD). It is not yet clear why some people cope well with disaster-related trauma while others experience chronic dysfunction. Prior research on non-disaster trauma suggests that an individual's history of traumatic experiences earlier in the life course, prior to the disaster, may be a key factor in explaining variability in psychological responses to disasters. This study evaluated the extent to which pre-disaster trauma predicts PTSD trajectories in a sample of Hurricane Katrina survivors followed for 12 years after the storm. Four PTSD trajectories were identified using latent class growth analysis: Resistant (49.0%), Recovery (29.3%), Delayed-Onset (8.0%), and Chronic-High (13.7%). After adjusting for covariates, pre-Katrina trauma had only a small, positive impact on the probability of long-term, chronic Katrina-specific PTSD, and little effect on the probability of the Resistant and Delayed-Onset trajectories. Higher pre-Katrina trauma exposure moderately decreased the probability of being in the Recovery trajectory, in which Katrina-specific PTSD symptoms are initially high before declining over time. When covariates were added to the model one at a time, the association between pre-Katrina trauma and Chronic-High PTSD was attenuated most by the addition of Katrina-related trauma. Our findings suggest that while pre-disaster trauma exposure does not have a strong direct effect on chronic Katrina-specific PTSD, pre-Katrina trauma may impact PTSD through other factors that affect Katrina-related PTSD, such as by increasing the severity of Katrina-related trauma. These findings have important implications for the development of disaster preparedness strategies to diminish the long-term burden of disaster-related PTSD.