What Triggers PTSD? Some people develop post-traumatic stress disorder (PTSD) after living through a shocking or dangerous experience. When you're in danger, your body's natural response is to feel scared.

That's when your body turns on its "fight or flight" response. In the face of something life-threatening, it revs up your heart rate, sends blood to your muscles to get ready to run, and amps up stress hormones to help fight off bleeding and infection in case you get hurt. Your brain tells your body that some of its functions are less important: Parts of the brain that store memory, emotion, and thinking get "turned off" for a little while.

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Normal emotions are shut off from the traumatic experience. That detachment from the memory and the experience can trigger PTSD after the event.

Causes of PTSD

All sorts of traumatic events can cause PTSD.

• Living through a violent act like rape, domestic violence, or sexual, physical, or verbal abuse
• Surviving a dangerous event like a car accident, natural disaster, or terrorist attack
• Being a part of combat or witnessing war as a civilian
• Being an emergency responder in a traumatic event
• Living through child neglect or abuse
• Experiencing the sudden death of a close friend or family member

In the first month after a severe traumatic event, symptoms similar to PTSD are called an "acute stress disorder." If those symptoms arise or persist beyond the first month -- or develop even years after the event -- the term PTSD is used. Not everyone who lives through or sees a scary or dangerous experience develops PTSD.

There are four main "clusters" of symptoms that define PTSD, including:

• Re-experiencing the traumatic event
• Hyper-arousal (muscular and emotional tension)
• Avoiding situations that may be reminders of the event
• Persistent negative effects on thinking and mood (e.g. emotional numbing)

To be diagnosed with PTSD, specific symptoms from the following list must occur and last at least a month:

• Bad dreams, memories, or flashbacks
• Being on edge and easily startled
• Feeling emotionally numb and losing interest in things you used to care about
• Problems sleeping
• Anger and irritability
• Hopelessness, depression, thoughts of suicide
• Panic attacks
• Physical symptoms (headaches, stomach pain, muscle aches, back pain, etc.)
• Avoiding places or events that are reminders of what happened