From National Institute of Mental Health (NIMH)

The National Institute of Mental Health (NIMH) is part of the National Institutes of Health (NIH), a component of the U.S. Department of Health and Human Services.

What is Post-Traumatic Stress Disorder?
Post-Traumatic Stress Disorder, PTSD, is an anxiety disorder that can develop after exposure to a terrifying event or ordeal in which grave physical harm occurred or was threatened. Traumatic events that may trigger PTSD include violent personal assaults, natural or human-caused disasters, accidents, or military combat.

Signs Symptoms
People with PTSD have persistent frightening thoughts and memories of their ordeal and feel emotionally numb, especially with people they were once close to. They may experience sleep problems, feel detached or numb, or be easily startled.

Treatment
Effective treatments for post-traumatic stress disorder are available, and research is yielding new, improved therapies that can help most people with PTSD and other anxiety disorders lead productive, fulfilling lives.