Posttraumatic stress disorder is an anxiety disorder that can develop after an individual is exposed to an extremely traumatic event that involved either direct personal experience of actual or threatened death or serious injury or witnessing an event that involved the death, injury or threat to the physical integrity of another person.

Symptoms of PTSD may develop immediately after a traumatic event or may have a delayed onset, defined as occurring when symptoms begin at least 6 months after the traumatic event.

This article describes the prevalence, risk factors, and symptoms of PTSD.


According to the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition, Text Revision), the lifetime prevalence for PTSD is approximately 8% of the adult population in the United States (prevalence rates for other countries are not available).

PTSD can occur at any age and can follow a natural disaster, a terrorist event, a war, a rape, a period of prison confinement, or any other potentially traumatic event.

The highest rates of PTSD are found among certain “at-risk” groups, such as survivors of rape, military combat and captivity, and ethnically or politically motivated internment and genocide.

Individuals who have recently emigrated from areas of social and civil unrest and conflict may be more likely to have elevated rates of PTSD. In children, the symptoms often manifest themselves in terms of repetitive play and bad dreams and nightmares, in addition to stomachaches and headaches.

Risk Factors

The cause of PTSD is unknown, but psychological, genetic, physical, and social factors are involved. PTSD changes the body’s response to stress and affects an individual’s stress hormones and neurotransmitters. Individuals who have been exposed to trauma in the past may be at an increased risk for developing PTSD.

Social support is an important protective factor against PTSD. In studies of Vietnam veterans, those with strong support systems were less likely to get PTSD than those without social support.

A recent study of PTSD in military personnel shows that pre-deployment psychiatric status is an important predictor of PTSD, with those who screened positive for mental health disorders before deployment being at an increased risk for developing PTSD upon return from deployment. Those who showed signs of PTSD before deployment were almost 5 times more likely to develop PTSD upon their return; those who showed signs of other mental health disorders (such as depression, panic disorder, or an anxiety disorder) were almost 2.5 times more likely to develop PTSD.


The symptoms of PTSD fall into three main categories, including a persistent and disruptive “reliving” of the event, avoidance, and arousal.

Repeated “reliving” of the event, which disturbs day-to-day activity

  • Recurrent and intrusive distressing recollections of the event, including images, thoughts, or perceptions
  • Recurrent distressing dreams or memories of the event
  • Acting or feeling as if the traumatic event were recurring
  • Flashback episodes, where the event seems to be happening over and over
  • Physical reactions to situations reminiscent of the traumatic event


  • Feelings of detachment or emotional numbing
  • Inability to remember important aspects of the trauma
  • Lack of interest in normal activities
  • Restriction of mood
  • Staying away from places, people, or objects that remind you of the event
  • Sense of having no future


  • Difficulty concentrating
  • Difficulty falling or staying asleep
  • Exaggerated startle response
  • Hypervigilance (excess awareness)
  • Irritability or outbursts of anger

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