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National Alliance on Mental Illness
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What is Posttraumatic Stress Disorder (PTSD)?

Though it may seem like a relatively simple concept, trauma—a powerful experience that may have long-lasting effects—has not always been defined the same. Scientists continue to study experiences of trauma in hopes of finding better treatments. One particular type of trauma is known as posttraumatic stress disorder (PTSD).

PTSD can affect many different people, from survivors of rape and survivors of natural disasters to military service men and women. Roughly 10 percent of women and 5 percent of men are diagnosed with PTSD in their lifetimes, and many others will experience some adverse effects from trauma at some point in their lives. According to the National institute of Mental Health (NIMH), about 1 in 30 adults in the U.S. suffer from PTSD in a given year—and that risk is much higher in veterans of war.

Not all “traumatic” events meet the clinical standards for trauma. The loss of a loved one or the limitations resulting from an illness may cause trauma but the shock of such events is not in itself abnormal. PTSD includes both an event that threatens injury to self or others and a response to those events that involves persistent fear, helplessness or horror.

Recent scientific understanding shows that experiencing traumatic events can change the way our brains function. Especially with severe or repeated exposure, the brain can be affected in such a way that makes a person feel like the event is happening again and again. Repeated experience of the traumatic event can prevent healing and keep a person stuck in a pattern that may induce anxiety, sleeplessness, anger or an increased possibility of substance abuse.

The Neurobiology of PTSD

People are programmed to respond to threats to their safety. Unfortunately, this set of adaptive responses in the face of terror, which are lifesaving in the moment, can leave people with ongoing, long-term psychological symptoms. The biological mechanisms that encourage the powerful and protective “fight or flight” response and maximize physical safety at the time, such as enabling a woman to fight off an attacker during a sexual assault, can create complex problems later.

When faced with terror, less critical body functions (e.g., the parts of the brain where memory, emotion and thinking are processed) get "turned off" in the service of immediate physical safety. Specifically, this “fight or flight” response increases the heart rate, moves more blood to muscles in order to run and adds stress hormones to help fight off infection and bleeding in case of a wound. As a result, the traumatic experiences are not integrated at the time they happen because the body is focusing entirely on immediate physical safety. A poorly integrated traumatic experience can be unpredictable and unexpected. The unprocessed memories of a traumatic event can occur without warning. As long as thoughts, memories and feelings associated with the trauma remain disconnected from the actual event, it is difficult for people living with PTSD to access their inner experiences because the normal flow of emotion remains deeply affected by the traumatic event.

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[Download the NAMI PTSD fact sheet.]

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