PTSD can develop after experiencing or witnessing a traumatic event like war, rape, natural disasters, or accidents. Symptoms include reliving the event through nightmares or flashbacks, feeling stressed and having sleep problems. Cognitive behavioral therapy and antidepressants can help patients cope by learning new skills to deal with triggers and negative thoughts. The disorder occurs when the body's fight-or-flight response activates when there is no real danger present. Not everyone who experiences trauma will get PTSD, and having social support acts as a protective factor against its development.