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Post Traumatic Stress Disorder (modern term: PTSD) is a mental disorder that can develop after a person is exposed to a very traumatic event, such as sexual assault, warfare, traffic collisions, or other threats on a person's life. Frequent among soldiers, it used to be called Shell Shock (World War I) and Combat Fatigue (World War II) in the past.
Symptoms may include: paranoia, overvigilance, concealment of handguns and other weapons for easy access, fear of unexisting treats, disturbing thoughts, feelings, or dreams related to the events (usually war flashbacks in most veterans); mental or physical distress to trauma-related cues; attempts to avoid trauma-related cues and alterations in how a person thinks and feels.
The most severe cases may feature trauma-related visual and auditory hallucinations with mental disturbances (such as severe depression) that could lead to suicide or full-on psychosis and loss of contact with reality.