Post-Traumatic Stress Disorder (PTSD) is a mental health condition that can develop after experiencing or witnessing a traumatic event. It involves a range of symptoms related to re-experiencing the event, avoidance of reminders, negative changes in thinking and mood, and increased arousal and reactivity. These symptoms must persist for at least a month and significantly interfere with daily life to be diagnosed as PTSD. 

There are 4 types of PTSD symptoms. To be diagnosed with PTSD, you need to have each type. That said, everyone experiences symptoms in their own way.

1. 1. 1. Reliving the event (also called re-experiencing symptoms). Memories of the traumatic event can come back at any time. They can feel very real and scary. For example:
         • You may have nightmares.
         • You may feel like you are going through the event again. This is called a flashback.
         • You may see, hear or smell something that causes you to relive the event. This is called a trauma reminder, cue or trigger. News reports, seeing an accident, or hearing fireworks are examples of trauma reminders.
      2. Avoiding things that remind you of the event. You may try to avoid situations or people remind you of the trauma event. You may even avoid talking or thinking about the event. For example:
         • You may avoid crowds because they feel dangerous.
         • You may avoid driving if you were in a car accident or if your military convoy was bombed.
         • If you were in an earthquake, you may avoid watching movies about earthquakes.
         • You may keep very busy or avoid getting help so you don’t have to think or talk about the event.
      3. Having more negative thoughts and feelings than before the event. The way you think about yourself and others may become more negative because of the trauma. For example:
         • You may feel numb—unable to have positive or loving feelings toward other people—and lose interest in things you used to enjoy.
         • You may forget about parts of the traumatic event or not be able to talk about them.
         • You may think the world is completely dangerous, and no one can be trusted.
         • You may feel guilt or shame about the event, wishing you had done more to keep it from happening.
      4. Feeling on edge or keyed up (also called hyperarousal). You may be jittery, or always alert and on the lookout for danger. You might suddenly become angry or irritable. For example:
         • You may have a hard time sleeping.
         • You may find it hard to concentrate.
         • You may be startled by a loud noise or surprise.
         • You might act in unhealthy ways, like smoking, abusing drugs or alcohol, or driving aggressively.

Anyone can develop PTSD at any age. Some factors can increase the chance that someone will have PTSD, many of which are not under that person’s control. For example, having a very intense or long-lasting traumatic event or getting injured during the event can make it more likely that a person will develop PTSD. PTSD is also more common after certain types of trauma, like combat and sexual assault.

Personal factors—like previous traumatic exposure, age and sex—can affect whether a person will develop PTSD. What happens after the traumatic event is also important. Stress can make PTSD more likely, while social support can make it less likely.