<Tr> <Th> Frequency </Th> <Td> 8.7% (lifetime risk); 3.5% (12 - month risk) (USA) </Td> </Tr> <Tr> <Td_colspan="2"> (edit on Wikidata) </Td> </Tr> <P> Posttraumatic stress disorder (PTSD) is a mental disorder that can develop after a person is exposed to a traumatic event, such as sexual assault, warfare, traffic collisions, or other threats on a person's life . Symptoms may include disturbing thoughts, feelings, or dreams related to the events, mental or physical distress to trauma - related cues, attempts to avoid trauma - related cues, alterations in how a person thinks and feels, and an increase in the fight - or - flight response . These symptoms last for more than a month after the event . Young children are less likely to show distress but instead may express their memories through play . A person with PTSD is at a higher risk for suicide and intentional self - harm . </P> <P> Most people who have experienced a traumatic event will not develop PTSD . People who experience interpersonal trauma (for example rape or child abuse) are more likely to develop PTSD, as compared to people who experience non-assault based trauma such as accidents and natural disasters . About half of people develop PTSD following rape . Children are less likely than adults to develop PTSD after trauma, especially if they are under ten years of age . Diagnosis is based on the presence of specific symptoms following a traumatic event . </P>

Which occurrence is a biologic indicator of posttraumatic stress disorder (ptsd)
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