Post Traumatic Stress Disorder can come from a lot of causes. It could be from the events of warfare, an automobile accident, a house fire, a disastrous weather event, a rape, or any number of things. It can create symptoms of flashbacks (frequently re-living the event) a heightened startle reflex, nightmares, and false emergency reactions when awakened.
It tends not to lessen greatly with time. At one time it was viewed as virtually untreatable, though many tried. Patients sometimes complained that the treatments only worsened their symptoms.
About 30 years ago that began to change. Maxine Shapiro developed EMDR, which provided a high percentage of permanentcures. Since then have come an alphabet soup of TFT, EFT, TAT, and UTW, which are fast and effective means of treating it.