Updated

Post-traumatic stress disorder (PTSD) is a psychological disorder that occurs in some people after witnessing or experiencing a traumatic event in which their life was on the line, according to the National Institute of Mental Health (NIMH) at the National Institutes of Health (NIH). 

Most sufferers of PTSD have witnessed or experienced acts of extreme violence, like assault or killing; others have lived through natural disasters or have unexpectedly lost a loved one. For many, the event doesn’t stop after they’ve survived—the distinguishing symptom of PTSD is having to relive the disaster over and over, sometimes for decades. That’s not the only symptom, though. Sufferers of PTSD often become isolated, irritable and defensive and tend to avoid normal activities.

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The Impact of PTSD

PTSD is commonly thought of as a military disorder, since those in the armed services are about twice as likely to develop it than noncombatants. However, sexual assault survivors also develop PTSD at very high rate. Additionally, women are twice as likely as men to develop symptoms after trauma. 

Children can also develop PTSD, although their symptoms (bed wetting, clinginess) may be quite different from teen and adult symptoms. Research suggests that susceptibility to the disorder may be genetic, and those with other mental illnesses are at increased risk, according to the NIH. However, most people who live through trauma will not develop PTSD.

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To be diagnosed with PTSD, a person must have symptoms of avoidance, hyper-arousal, and re-experiencing for at least one month, no matter how long after the trauma they start showing symptoms, according to the NIH. If symptoms are shorter-lived than one month, acute stress disorder (ASD) is usually diagnosed.

Like most psychological disorders, PTSD also affects the family and friends of the diagnosed and takes a toll on relationships. Sufferers of PTSD are more likely to attempt suicide. It also can lead to other mental illnesses like depression, anxiety and substance abuse.

READ MORE: Study finds millions of Americans with depression go untreated

When it comes to PTSD in the military, not all circumstances are created equal. People who experience a traumatic brain injury are much more likely to develop PTSD, according to the National Council on Disability.

Trauma, PTSD, and Veterans, by the Numbers

30.9
Minimum percentage of Vietnam veterans who suffered from PTSD at some point.

84.8
Percentage of PTSD-diagnosed Vietnam veterans currently suffering more than slight impairment, 30+ years after combat.

12,632
Number of Iraq and Afghanistan veterans diagnosed with PTSD in 2013.

49
Estimated percentage of rape survivors who have PTSD symptoms at some point.

5.2 million
Number of adults who will have some form of PTSD this year.

50
Percentage of Americans with PTSD who ever seek treatment.

21
Percentage of Americans with PTSD receiving minimally adequate treatment.

While these numbers can be jarring to look at, perhaps the most upsetting is the last figure: Just over 1 in 5 Americans living with PTSD receive minimally adequate treatment, according to a survey in JAMA Psychiatry. “Minimally adequate” treatment is defined by current psychiatric guidelines, and includes either four hours of psychotherapy or two months of appropriate prescription drugs.

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Why are so few with PTSD getting the minimal treatment they need? For some, symptoms are mild enough that they may not know they have PTSD. For others, ongoing research, including broad veterans’ surveys, indicates that pride and trust may be the culprit.

Fewer than half of soldiers seek treatment for PTSD, and 20 to 50 percent of those drop out early due to the lack of trust in mental health professionals, the belief that symptoms will work themselves out and the notion that treatment should be a last resort, according to research presented at the American Psychiatric Association’s 2012 annual meeting. This belief isn’t entirely false—PTSD can resolve on its own. But treatment can accelerate the healing process or provide relief in cases where it might have been a lifelong problem.

Lacie Glover writes for NerdWallet Health, a website that empowers consumers to find high quality, affordable health care and insurance.