These traits do not necessarily occur in people with obsessive-compulsive disorder, which is a psychiatric condition. The event that precipitates PTSD is usually thought to be outside the norm of human experience, such as sexual assault or combat. Studies indicate, however, that the condition may be very common. It may develop in people who witness accidents, who or are involved with rescues, or who lose loved ones suddenly. It may also occur in people who have serious illness and receive aggressive treatments or who have close family members or friends with such conditions.
Symptoms can occur weeks, months, or even years after the traumatic event.
The patient struggles to forget the traumatic event and frequently develops emotional numbness and event-related amnesia. Often, however, the PTSD patient suffers a mental flashback and re-experiences the painful circumstance in the form of intrusive dreams or disturbing thoughts and memories, which resemble or recall the trauma. They are often quick to startle or be angry, even from minor matters.