Post traumatic stress disorder is a mental illness which occurs following a life threatening event like accidents, sexual assault, war, witnessing death or torture, natural calamities like tsunami, earth quake, floods, etc.
Symptoms include reliving the event in the form of memories, flashbacks or nightmares accompanied by heightened emotions, emotional numbing, avoidance of stimuli triggering memories of the event, being hyper alert and fear of threat. They may also have guilt, secondary depressive and anxiety symptoms, may also use drugs in an attempt to reduce their emotional turmoil.
It is important to recognize this early and seek help. Treatment is availabel in the form of various psychotherapies (cognitive therapy, behavior therpay, EMDR) and medications.