Merck Manual

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Posttraumatic Stress Disorder (PTSD)


John W. Barnhill

, MD, New York-Presbyterian Hospital

Full review/revision Apr 2020 | Modified Sep 2022
Topic Resources

Posttraumatic stress disorder (PTSD) involves intense, unpleasant, and dysfunctional reactions beginning after an overwhelming traumatic event.

  • Events that threaten death or serious injury can cause intense, long-lasting distress.

  • Affected people may relive the event, have nightmares, and avoid anything that reminds them of the event.

  • Treatment may include psychotherapy (supportive and exposure therapy) and antidepressants.

When terrible things happen, many people are lastingly affected. In some, the effects are so persistent and severe that they are debilitating and constitute a disorder. Generally, events likely to cause PTSD are those that invoke feelings of fear, helplessness, or horror. Combat, sexual assault, and natural or man-made disasters are common causes of PTSD. However, it can result from any experience that feels overwhelming and life threatening, such as physical violence or an automobile crash.

These events may be experienced directly (such as having a serious injury or being threatened with death) or indirectly (witnessing others being seriously injured, killed, or threatened with death; or learning of traumatic events that occurred to close family members or friends). People may have experienced a single trauma or, as is common, multiple traumas.

Overview of Posttraumatic Stress Disorder

It is not known why the same traumatic event may cause no symptoms in one person and lifelong PTSD in another. Nor is it known why some people witness or experience the same trauma many times over years without developing PTSD, but then develop it following an apparently similar episode.

Chronic posttraumatic stress disorder may not disappear but often becomes less intense over time even without treatment. Nevertheless, some people remain severely handicapped by the disorder.

Symptoms of PTSD

People with posttraumatic stress disorder (PTSD) typically have symptoms from each of the following four categories:

  • Intrusion symptoms (the event repeatedly and uncontrollably invades their thoughts)

  • Avoidance of anything that reminds them of the event

  • Negative effects on thinking and mood

  • Changes in alertness and reactions

Intrusion symptoms

The traumatic event may repeatedly reappear in the form of involuntary, unwanted memories or recurrent nightmares. Some people have flashbacks, in which they relive events as if they were actually happening rather than simply being remembered.

People may also experience intense reactions to reminders of the event. A combat veteran's symptoms might be triggered by fireworks, for example, whereas those of a robbery victim may be triggered by seeing a gun in a movie.

Avoidance symptoms

People persistently avoid things—activities, situations, or people—that are reminders of the trauma. For example, they may avoid entering a park or an office building where they were assaulted or avoid speaking to people of the same race as their assailant. They may even attempt to avoid thoughts, feelings, or conversations about the traumatic event.

Negative effects on thinking and mood

How people think about the event may become distorted, leading them to blame themselves or others for what happened. Feelings of guilt are also common. For example, they may feel guilty that they survived when other people did not. They may feel only negative emotions, such as fear, horror, anger, or shame, and may be unable to feel happy or satisfied or to love.

Changes in alertness and reactions

People may have difficulty falling asleep or concentrating.

They may become excessively vigilant for warning signs of risk. They may be easily startled.

People may become less able to control their reactions, resulting in reckless behavior or angry outbursts.

Other symptoms

Some people develop ritual activities to help reduce their anxiety. For example, people who were sexually assaulted may bathe repeatedly to try to remove the sense of being unclean.

Diagnosis of PTSD

  • A doctor's evaluation, based on specific criteria

Doctors diagnose posttraumatic stress disorder (PTSD) when

  • People have been exposed directly or indirectly to a traumatic event.

  • Symptoms have been present for 1 month or longer.

  • Symptoms cause significant distress or significantly impair functioning.

  • People have some symptoms from each of the categories of symptoms associated with PTSD (intrusion symptoms, avoidance symptoms, negative effects on thinking and mood, and changes in alertness and reactions).

Doctors also check to see whether symptoms could result from use of a drug or another disorder.

PTSD often is not diagnosed because it causes such varied and complex symptoms. Also, the presence of a substance use disorder Substance Use Disorders Substance use disorders generally involve behavior patterns in which people continue to use a substance (for example, a recreational drug) despite having problems caused by its use. The substances... read more can distract attention from the PTSD. When diagnosis and treatment are delayed, PTSD can become chronically debilitating.

Treatment of PTSD

  • Psychotherapy

  • Drug therapy

  • Treatment of other disorders, such as substance use or major depression


Psychotherapy is central to the treatment of posttraumatic stress disorder (PTSD).

Education about PTSD can be an important early step in therapy. The symptoms of PTSD can feel overwhelmingly confusing, and it is often very useful for people and loved ones to understand how PTSD can include seemingly unrelated symptoms.

Stress management techniques, such as breathing and relaxation, are important. Exercises that reduce and control anxiety (for example, yoga, meditation) can relieve symptoms and also prepare people for treatment that involves stress-inducing exposure to memories of the trauma.

In exposure therapy, the therapist has people imagine being in situations associated with prior trauma. For example, they may be asked to imagine visiting a park where they were assaulted. The therapist may help people reimagine the traumatic event itself. Because of the often intense anxiety associated with traumatic memories, it is important for the people to feel supported and for the exposure to proceed at the right pace. People who have been traumatized may be especially sensitive to being traumatized again, so treatment can get stalled if it goes too quickly. Often, treatment may shift from exposure to a more supportive, open-ended treatment, to help people be more comfortable with exposure therapy.

Broader and more exploratory psychotherapy may also ease return to a happier life, such as by focusing on relationships that may have been fractured by PTSD. Other types of supportive and psychodynamic psychotherapy can also be useful as long as they do not shift the focus of treatment away from exposure therapy.

Eye movement desensitization and reprocessing (EMDR) is treatment in which people are asked to follow the therapist's moving finger while they imagine being exposed to the trauma. Some experts think that the eye movements themselves help with desensitization, but EMDR probably works mainly because of the exposure, not the eye movements.

Drug therapy

Antidepressants are considered first-line treatment for PTSD, even in people who do not also have major depression Depression A short discussion of prolonged grief disorder. Depression is a feeling of sadness and/or a decreased interest or pleasure in activities that becomes a disorder when it is intense enough to... read more . Selective serotonin reuptake inhibitors and other antidepressants such as mirtazapine and venlafaxine are most often recommended.

To treat insomnia and nightmares, doctors sometimes give drugs such as olanzapine and quetiapine (also used as antipsychotic drugs Antipsychotic drugs Schizophrenia is a mental disorder characterized by loss of contact with reality (psychosis), hallucinations (usually, hearing voices), firmly held false beliefs (delusions), abnormal thinking... read more ) or prazosin (also used to treat high blood pressure). However, these drugs do not treat PTSD itself.

More Information about PTSD

Drugs Mentioned In This Article

Generic Name Select Brand Names
Remeron, Remeron SolTab
Effexor, Effexor XR, Venlafaxine
Zyprexa, Zyprexa Intramuscular, Zyprexa Relprevv, Zyprexa Zydis
Seroquel, Seroquel XR
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