There are four categories of PTSD symptoms:

Intrusive thoughts

Intrusive thoughts could be nightmares or being unable to stop thinking about the event, but the most well-known of these symptoms is the flashback. When a sight or sound triggers a flashback, the experience can be so vivid you feel like you’re reliving the original trauma itself.

Avoidance

To prevent unwelcome reminders and flashbacks, people who have PTSD often start to avoid anything that could trigger these intrusive thoughts. You might avoid:

• People
• Places
• Activities
• Objects 

This can result in you withdrawing from life and closing down, so you avoid talking about what happened as well.

Negative thoughts and feelings

You might develop distorted beliefs, for example, thinking you are to blame or that something similar is going to happen to you again. You stop enjoying the activities that made you happy and start feeling detached from people you’re close to. 

It’s common when you have PTSD to feel anger and fear, and be unable to let go of the horror that you experienced.

Arousal and reactive symptoms

Typical arousal and reactive symptoms include:

• Irritability
• Angry outbursts
• Reckless behavior
• Self-destructive behavior
• Being easily startled
• Problems concentrating
• Sleep disruption

You might develop symptoms soon after the event, but in many cases, symptoms don’t appear until much later. It’s common for people to feel these kinds of symptoms in the aftermath of a trauma, known as an acute stress disorder, but these feelings usually reduce over time. If you’re still feeling the same way after a month or more, it could be because acute stress disorder progressed to PTSD.