Is it in Your Genes: Post-Traumatic Stress Disorder

Post-Traumatic Stress Disorder. <http://paradigmmalibu.com/teen-post-traumatic-stress-disorder>

Since October 2001, approximately 1.7 million U.S. troops have deployed as part of Operation Enduring Freedom (OEF; Afghanistan) and Operation Iraqi Freedom (OIF; Iraq). The deployment pace in these recent conflicts is unprecedented, with more service members deployed for longer periods of time. At the same time, advances in both medical science and military technology have dramatically reduced casualty rates of killed or wounded.1 This means more service members are surviving experiences that would have led to death in the earlier prolonged wars, such as Vietnam and Korea War. Casualties of a different kind have emerged, however - invisible wounds such as post-traumatic stress disorder.



Post-traumatic stress disorder (PTSD) may develop after a person is exposed to one or more traumatic incidents including sexual assault, torture, child abuse, car accident, natural disaster, or combat during war. The person who develops PTSD may have been the one who was harmed, or the person may have witnessed a harmful event that happened to others. In the typical case, the individual with PTSD persistently avoids all thoughts, emotions, and discussion of the stressor event and may experience amnesia for it. However, the event is commonly relived by the individual through intrusive flashbacks, nightmares, and extreme emotional and physical reactions to reminders of the event. Other common symptoms linked with PTSD include panic attacks, depression, suicidal impulses, drug abuse, and isolation.

According to data published by PTSD Alliance and U.S. Department of Veterans Affairs, 70 percent of adults in the United States have experienced a traumatic event at least once in their lives, and up to 20 percent of these people will develop post-traumatic stress disorder. At any given time, more than 13 million Americans have PTSD (or 7-8% of the population). It is easy to imagine then, with increasing survival rates in combats, PTSD among war veterans returning to society is becoming more prevalent. About 12% of Gulf War Veterans while 11-20% of Afghanistan and Iraq Veterans have PTSD in a given year. 2,3 The two-year post-deployment costs to society resulting from PTSD for the 1.7 million deployed service members are estimated to range from $4.0 to $6.2 billion, and because this estimate does not account for costs that may arise after two years, it underestimates the total cost.1

War veterans are most vulnerable to PTSD. <https://pointsadhsblog.wordpress.com/2011/11/30/down-to-earth-rick-doblin-on-maps-basic-philosophies-and-day-to-day-operations>

The idea that your genes play a role in whether you develop PTSD is a popular focus of recent research. Studies of twins show that genetic factors account for about 30% of the differences in response to trauma, with identical twins much more likely to both develop PTSD than fraternal twins.4 

Roee Admon, along with his colleagues at Harvard Medical School, proposed a new PTSD model, according to which, changes in two brain areas - the amygdala and the dorsal anterior cingulated cortex (dACC) - may predispose people to PTSD. Both regions of the brain are involved in feeling and expressing fear, and both appear to be over-activated in people with PTSD even before they develop the condition. The heightened activity in the amygdala and the dACC may contribute to one of the hallmarks of PTSD, called hyperarousal, which can cause people to be irritable or easily startled. Individual differences in genes, along with earlier life experiences, may lead to increased activity in the amygdala and dACC.5

Another area of focus is genes that play a role in creating fear memories. Understanding how fear memories are created may help to fine measures for reducing the symptoms of PTSD. Researchers have found genes that make stathmin, a protein needed to form fear memories. Mice that do not make stathmin are less likely than normal mice to "freeze," a natural protective response to danger, after being exposed to a fearful experience. They also showed less innate fear by exploring open spaces more willingly than normal mice.5

The complete mechanism of how post-traumatic stress disorder develops is yet unknown. It is likely that many genes will small effects are at work in PTSD. However, many ongoing researches focus on discovering genes that cause an individual to become prone to develop PTSD. At current rate of ongoing research, we may soon be able to predict who is at risk for PTSD before they experience a traumatic event, as well as treat people at the right time after trauma to prevent subsequent development of PTSD.

                              
1. Tanielian, Terri. Assessing Combat Exposure and Post-Traumatic Stress Disorder in Troops and Estimating the Costs to Society, Invisible Wounds of War Study, RAND., Mar. 2009. <http://www.rand.org/content/dam/rand/pubs/testimonies/2009/RAND_CT321.pdf>.

2. Epidemiology of PTSD, PTSD: National Center for PTSD, US. Department of Veterans Affairs, Nov. 2014. <http://www.ptsd.va.gov/public/PTSD-overview/basics/how-common-is-ptsd.asp>.

3. Statistics on PTSD, PTSD Allaince, Beachway Therapy Center, 2001. <http://www.ptsdalliance.org>.

4. Stein, M.B., Jang, K.L., Taylor, S., Vernon, P.A., Livesley, W.J., Genetic and environmental influences on trauma exposure and post-traumatic stress disorder symptoms: a twin study, Oct. 2002, The American Journal of Psychiatry.

5. Rettner, Rachael. Unraveling PTSD: New Look Reveals How Disorder May Progress, Livescience, Jul. 2013. <http://www.livescience.com/38038-ptsd-develops-model.html>.