Approximately 10 percent of people suffer from post-traumatic stress disorder (PTSD) after experiencing a severe trauma, while others go on to experience varying levels of emotional stress. Around one-third of those who develop PTSD will have symptoms for the rest of their lifetimes, while others are able to recover fully from a severely traumatic event or series of events. Why do some people come through severe trauma with the ability to function relatively normally, while others suffer serious and sometimes permanent psychological disorders? The question of why some people are more resilient to traumatic experiences is of great interest to researchers because they believe it could help to treat and perhaps prevent PTSD. What Is Resilience? Resilience to traumatic experiences does not mean that resilient individuals are totally unaffected by severe trauma. Instead, resilience refers to the ability that some people have to adapt after trauma so that they are able to function normally and eventually have a full emotional recovery. Characteristics of resilience include positivity and optimism, the ability to reframe traumatic experiences in a positive light, the ability to perceive traumatic experiences in less threatening ways, social skills that allow people to have large and supportive social networks, and lower levels of denial and avoidance. Biological Contributors to Resilience Studies have found that resilience to trauma appears to come from a combination of genetic, environmental and behavioral factors. While some biological factors that have been linked to resilience appear to be genetically determined, others can be influenced by early childhood experiences and behaviors. One major genetic contributor to resiliency appears to be a compound known as neuropeptide Y (NPY). NPY has been associated with reduced levels of anxiety in the face of stress in studies involving both humans and rodents. One study found that Special Forces soldiers with higher levels of NPY performed better during rigorous training, and another study found that combat veterans without PTSD had higher levels of NPY than combat veterans suffering from PTSD. Some studies have demonstrated that resilience may be strongly connected to a well-functioning acute stress response. Our acute stress response is often referred to as the \u201cfight-or-flight response,\u201d and it is the reaction that causes the human body to get a rush of adrenaline and a burst of energy and alertness when faced with danger. Researchers have found that resilience is associated with acute stress responses that activate quickly and also come back under control quickly. Panic attacks are an example of a malfunctioning acute stress reaction\u2014the body responds physically as though extreme danger is present, and the response continues for a long time even though there is no threat. In contrast, people who have rapid reactions to danger but also recover quickly appear to have more resilience. Behavior, Experiences Influence Biological Responses Rodent studies have suggested that nurturing environments during childhood result in lower levels of anxiety during adulthood. This positive influence of social support is also seen later in life; people with supportive family and friend groups are better able to adapt and recover following severe trauma than people who are comparatively socially isolated. Certain kinds of psychotherapy also seem to be able to influence physiological stress responses and help people become more resilient. Treatment approaches such as cognitive behavioral therapy can be used to increase positive thinking and optimism and help people gain a sense of meaning and purpose following trauma. The more researchers understand how genetics, behavior and environment interact following severe stress, the better different treatments will be able to promote resilience in all people recovering from trauma.