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The Neuroscience of High-Risk Behaviors Associated with Combat Post-Traumatic Stress Disorder

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Post-traumatic stress disorder (PTSD) is an anxiety disorder defined as a persistent re-experiencing of a traumatic event that a person has been the victim of or witnessed. To be classified by the DSM-IV TR, a person must have recurrent or intrusive recollections of the event, intense psychological distress and physiological reactivity to internal or external cues that symbolize the event, and increased arousal (not present prior to the event) which last more than one month.

Combat is a classic example of a traumatic event that may trigger PTSD given that the horrors of war are outside the range of normal human experience. Americans primarily learn about the experience of war through media, but the reality is much bleaker and the scenarios soldiers bare witness to are more dire than most people assume. The All-American, boy-next-door sent to the Middle East for several tours will not return the same person; combat will forever change him. For instance, imagine you are supposed to do a security sweep, but your commander asks you to stay at the base instead. Then, an insurgent kills the man who goes in your place. One life ends, unfulfilled while you carry the burden of guilt for the rest of your life.

Stories like this are common among veterans yet, most times go unspoken with family and friends upon returning home. A veteran may undoubtedly have trouble returning to normal life and one of the key indicators of PTSD is disinterest in activities that he/she formerly enjoyed. This numbing of general responsiveness is characterized by detachment from others, restricted range of affect, and an inability to envision a career, marriage, or future.

It is estimated that PTSD occurs in 11-20% of veterans of the Iraq and Afghanistan wars, Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF). The onset of PTSD can occur within weeks, to even months or years after returning stateside. Some factors that affect the onset of PTSD include the intensity of the trauma, closeness to the event or people involved, and support received following the event.

Although less than 1% of the Americans are OIF/OEF veterans, it is pertinent to research the factors that impact the mental health of this important population. PTSD is often stigmatized in our culture due to lack of awareness about this socially and occupationally impairing disorder. Thus, the following review of recent literature investigates neurological and behavioral aspects of PTSD.

To date, much of the research on combat PTSD focuses on the increased prevalence of high-risk health behaviors, particularly alcohol/substance usage and physical fighting. Combat PTSD was linked to a significant increased risk of being involved in a physical fight in a sample of OEF/OIF veterans attending college (Widome et al, 2011). Analysis also indicated a marginal association between high-risk drinking and veterans with PTSD, compared to non-veterans and veterans without PTSD. These findings suggest that PTSD is related to several dangerous health risks, which should be considered when evaluating the mental and physical health needs of the OEF/OIF veteran population.

PTSD generally precedes substance use in a self-medicating effort to improve arousal-related symptoms and numb distressing emotions. In a recent study, Yan et al. (2013) investigated neurological activity of combat veterans with and without PTSD. Using functional MRI imaging, researchers found that combat veterans with PTSD have increased amygdala activity and decreased thalamus activity in both provocation states and resting states.

The amygdala plays a primary role in emotional reactions; therefore dysregulation affects the storing and recalling of emotional memories. Sensory perception and regulation of alertness, sleepiness, and consciousness are controlled by the thalamus. The findings of this study show suggest that the amygdala and thalamus are the major neurological structures contributing to the hyperarousal symptoms and re-experiencing symptoms of PTSD. This constant, abnormal neurological state interferes with a one's sleeping, eating, and concentration.

Nunnink et al. (2010) investigated the relationship between symptom clusters of PTSD and sexual problems using large, mental health-screening questionnaire of veterans in OIF/OEF. Sexual problems were defined as erectile dysfunction, sexual disinterest, and avoidance of sex. Symptom severity was measured for four symptom clusters: (1) numbing, (2) avoidance, (3) hyperarousal, and (4) re-experiencing.

As hypothesized, only emotional numbing significantly predicted sexual problems. Therefore, veterans of Afghanistan and Iraq wars whose predominant symptom of PTSD is emotional numbing have higher rates of sexual problems than those who experience hyperarousal, re-experiencing, or avoidance. The findings indicate that the emotional deficits associated with PTSD can seriously strain a veteran's sexual relationships.

Different high-risk behaviors are associated with certain symptom clusters of PTSD. Based on prior studies of the neurological basis of PTSD, Lanius et al. (2011) proposes a two-subtype distinction based on symptoms: (1) dissociative and (2) intrusive/hyperaroused. The dissociative category includes emotional numbing, detachment, and loss of interest symptoms whereas a veteran who re-experiences and becomes physiologically reactive to trauma-related cues is categorized as intrusive.

Functional MRI studies in which soldiers become hyperaroused when recalling traumatic events, showed increased activity in the amygdala but low activation in the prefrontal cortex. In contrast, emotional numbing showed hyperinhibited limbic activity (amygdala) but overactivation in the prefrontal cortex. These findings suggest the dysregulation of the prefrontal cortex and amygdala play a primary role in the type of symptoms expressed.

In summary, combat PTSD is a debilitating anxiety disorder that plagues the everyday lives of up to 20% of OIF/OEF war veterans. Studies reviewed in this paper support the argument that those who experience mostly emotional numbing symptoms are at risk for sexual health problems stemming from an overactive prefrontal cortex that hyperinhibits the emotional recalling area of the brain, the amygdala. Other PTSD veterans with mostly re-experiencing and hyperarousal symptoms may be at a greater risk for substance/alcohol use and physical fighting problems.

Future studies could use fMRI findings to predict the major symptoms of a PTSD diagnosis and thereby, pre-emptively address the high-risk behaviors correlated with each symptom cluster. Further, research should identify the neurobiological pathways of the sexual problems and health-risk behaviors associated with each symptom cluster. Findings of such research could have important implications in the pharmaceutical treatment of PTSD. Given the significant impact this disorder has on social and occupational functioning, more effective evidence-based treatment guidelines should be developed.

By Abby Johnston

Abby Johnston is a Graduate of Duke University with a B.S. in Psychology. While at Duke, Abby was a 3 time National Champion in diving and a member of the U.S. Olympic Team at the London Olympics in 2012. She won a Silver Medal at the London Olympics in 2012 in the Women's Synchronized 3-Meter Springboard Diving.

References:

1. Center for Substance Abuse Treatment. Substance Abuse Treatment: Addressing the Specific Needs of Women. Rockville (MD): Substance Abuse and Mental Health Services Administration (US); 2009. (Treatment Improvement Protocol (TIP) Series, No. 51.) Appendix E: DSM-IV-TR Criteria for Posttraumatic Stress Disorder. Available from: http://www.ncbi.nlm.nih.gov/books/NBK83241/

2. Lanius, R., Vermetten, E., Loewenstein, R., Brand, B., Schmahl, C., Bremner, J., & Spiegel, D. (2010). Emotion modulation in PTSD: Clinical and neurobiological evidence for a dissociative subtype. The American Journal Of Psychiatry, 167(6), 640-647. doi:10.1176/appi.ajp.2009.09081168

3. Nunnink, S. E., Goldwaser, G., Afari, N., Nievergelt, C. M., & Baker, D. G. (2010). The Role of Emotional Numbing in Sexual Functioning Among Veterans of the Iraq and Afghanistan Wars. Military Medicine, 175(6), 424-428.

4. US Department of Veteran Affairs; National Center for PTSD. PTSD Overview and Research. 7/22/2011. http://www.ptsd.va.gov/public/pages/ptsd_research.asp

5. Widome, R., Kehle, S. M., Carlson, K. F., Laska, M., Gulden, A., & Lust, K. (2011). Post-Traumatic Stress Disorder and Health Risk Behaviors among Afghanistan and Iraq War Veterans Attending College. American Journal Of Health Behavior, 35(4), 387-392.

6. Yan, X., Brown, A. D., Lazar, M., Cressman, V. L., Henn-Haase, C., Neylan, T. C., ... & Marmar, C. R. (2013). Spontaneous brain activity in combat related PTSD. Neuroscience letters.