Yes, a car accident can cause you to develop PTSD (post traumatic stress disorder). When you are involved in a car accident, it can be life-threatening, and the images of the accident can be horrific. Because of this, you can have recollections of the accident, via flashbacks during the day (like a movie playing in your head), or nightmares when you go to sleep. You might also avoid anything that reminds you of the accident, and avoid the actual scene of the accident. You might also become hypervigilant and constantly on-guard for any signs of further danger.