Post-traumatic stress disorder (PTSD) is often experienced by individuals who have experienced or witnessed a tragic event. The situation leading to PTSD can be anything traumatic, from a car accident to military deployment to a combat zone. Witnessing an assault, experiencing a severe injury or even enduring an especially difficult childbirth can lead to PTSD. Not everyone who experiences a tragedy can be immediately diagnosed for PTSD. Many people may be exposed to the same traumatic event and have varying ways of processing and dealing with the emotions and physical effects of the situation. In addition, even among those who experience the symptoms of PTSD, there is a wide range of severity and of specific symptoms. Flashbacks, insomnia and anxiety are common problems that are used to diagnose PTSD, but patients may report varying combinations and symptoms. A recent study sought to understand whether there were patterns in research that may give clues to factors that influence the development of PTSD. Specifically, the researchers wanted to find out whether the type of disaster or severity of a disaster might impact the likelihood that an individual would develop PTSD. Broadening the understanding of what factors may predict the onset of PTSD could help clinicians identify the individuals most at risk for the disorder. Led by Carol S. North of the Department of Psychiatry and Surgery at the University of Texas Southwestern Medical Center, the study was a review of previous research compiled on PTSD occurring related to ten separate disasters. The research focused on the experiences of 811 survivors of disasters. The review included measures of exposure factors and demographic information. The results of the analysis showed that the type of disaster did not predict PTSD. However, several demographic factors, such as age and gender did impact the occurrence of PTSD. North explained that among the results, individuals who had experienced the same event were shown to have varied mental health outcomes. Disasters of the same type carried a wide variety when it came to the impact on mental health of the survivors. The study found that being young, female and Hispanic were all predictors of PTSD. In addition, situations in which an individual with a low-level education witness a death or injury were predictive of PTSD. If an individual had a mental health disorder before the experience of the disaster, they were also more likely to develop PTSD, as well as individuals who used avoidance as a way to cope with the disaster's effects. The review found that overall, about two-thirds of the survivors did not exhibit any signs of psychological distress following the disaster. Among survivors who did experience a mental health condition, PTSD was the most common reported. Depression was the second-most reported mental health condition. The study's findings appear in a recent issue of the American Journal of Public Health.