Posttraumatic stress disorder may develop after a person is exposed to one or more traumatic events, such as sexual assault, warfare, serious injury, or threats of imminent death. The diagnosis may be given when a group of symptoms, such as disturbing recurring flashbacks, avoidance or numbing of memories of the event, and hyperarousal, continue for more than a month after the occurrence of a traumatic event. Most people having experienced a traumatizing event will not develop PTSD. People who experience assault-based trauma are more likely to develop PTSD, as opposed to people who experience non-assault based trauma such as witnessing trauma, accidents, and fire events. Children are less likely to experience PTSD after trauma than adults, especially if they are under ten years of age. War veterans are commonly at risk for PTSD.