PTSD is a psychological response to the experience of intense traumatic events, including those that threaten life. For military veterans, the trauma may relate to direct combat duties, being in a dangerous war zone, or taking part in peacekeeping missions under difficult and stressful conditions.
It is normal to experience distress when confronted with trauma, and most people recover over the first week or two, particularly with the help of caring family members and friends. However, for some people the symptoms do not seem to resolve quickly. It is also common for symptoms to vary in intensity over time. Some people go for long periods without any significant problems, only to relapse when they have to deal with other major life stresses. In rare cases, the symptoms may not appear for months, or even years, after the trauma.
Keep reading at https://www.dva.gov.au/health-and-wellbeing/mental-health/posttraumatic-stress-disorder-ptsd