No abstract

Mild traumatic brain injury (mTBI) has gained considerable notoriety during the past decade of conflict in Afghanistan and Iraq. However, the relationship between combat-related mTBI and residual mTBI symptoms, post-traumatic stress disorder (PTSD) symptoms, and neurocognitive deficits remains unclear. The purpose of the study was to compare residual mTBI and PTSD symptoms, and neurocognitive deficits among U.S. Army Special Operations Command (USASOC) personnel with diagnosed blunt, blast, and blast-blunt combination mTBIs. This study involved a retrospective medical records review of 27,169 USASOC personnel who completed a military version of the Immediate Post-Concussion Assessment Cognitive Test (ImPACT), Post-Concussion Symptom Scale (PCSS), and PTSD Checklist (PCL) between November 2009 and December 2011. Of the 22,203 personnel who met criteria for the study, 2,813 (12.7%) had a diagnosis of at least one mTBI. A total of 28% (n=410) of USASOC personnel with a history of diagnosed mTBI reported clinical levels of PTSD symptoms. Personnel with a history of diagnosed blunt (OR=3.58), blast (OR=4.23) or combination (OR=5.73) mTBI were at significantly (p=0.001) greater risk of reporting clinical levels of PTSD symptoms than those with no history of mTBI. A dose-response gradient for exposure to blast/combination mTBI on clinical levels of PTSD symptoms was also significant (p=0.001). Individuals with blast/combination mTBIs scored higher in residual mTBI (p=0.001) and PTSD symptoms (p=0.001), and performed worse on tests of visual memory (p=0.001), and reaction time (p=0.001) than those with blunt or no mTBI history. Individuals with combination mTBIs scored lower in verbal memory (p=0.02) than those with blunt mTBIs. Residual PTSD and mTBI symptoms appear to be more prevalent in personnel with blast mTBI. A dose-response gradient for blast mTBI and symptoms suggests that repeated exposures to these injuries may have lingering effects.

Posttraumatic stress disorder (PTSD), a trauma-related mental disorder, is associated with mitochondrial dysfunction in the brain. However, the biologic approach to identifying the mitochondria-focused genes underlying the pathogenesis of PTSD is still in its infancy. Previous research, using a human mitochondria-focused cDNA microarray (hMitChip3) found dysregulated mitochondria-focused genes present in postmortem brains of PTSD patients, indicating that those genes might be PTSD-related biomarkers. To further test this idea, this research examines profiles of mitochondria-focused gene expression in the stressed-rodent model (inescapable tail shock in rats), which shows characteristics of PTSD-like behaviors and also in the blood of subjects with PTSD. This study found that 34 mitochondria-focused genes being upregulated in stressed-rat amygdala. Ten common pathways, including fatty acid metabolism and peroxisome proliferator-activated receptors (PPAR) pathways were dysregulated in the amygdala of the stressed rats. Carnitine palmitoyltransferase 1B (CPT1B), an enzyme in the fatty acid metabolism and PPAR pathways, was significantly over-expressed in the amygdala (P<0.007) and in the blood (P<0.01) of stressed rats compared with non-stressed controls. In human subjects with (n=28) or without PTSD (n=31), significant over-expression of CPT1B in PTSD was also observed in the two common dysregulated pathways: fatty acid metabolism (P=0.0027, false discovery rate (FDR)=0.043) and PPAR (P=0.006, FDR=0.08). Quantitative real-time polymerase chain reaction validated the microarray findings and the CPT1B result. These findings indicate that blood can be used as a specimen in the search for PTSD biomarkers in fatty acid metabolism and PPAR pathways, and, in addition, that CPT1B may contribute to the pathology of PTSD.

This study examined the association between specific combat experiences and postdeployment hazardous drinking patterns on selected military populations that are considered high risk, such as personnel belonging to U.S. Army Special Operations Forces. Data collection were conducted in a 5-year span in which 1,323 Special Operations Forces Soldiers were surveyed anonymously from 3 to 6 months after returning from deployment to Iraq/Afghanistan regarding their combat experiences and mental health. Combat items were independently analyzed and placed into the following categories: (1) Fighting, (2) Killing, (3) Threat to oneself, (4) Death/Injury of others, and (5) Atrocities. Alcohol misuse was measured using the Alcohol Use Disorders Identification Test-Consumption. Of the Soldiers sampled, 15% (N = 201) screened positive for alcohol misuse 3 to 6 months postdeployment. Combat experiences relating to fighting, threat to oneself, and atrocities were significantly related to alcohol misuse when analyzed individually. However, when factors were analyzed simultaneously, combat experiences in the fighting category were significantly associated with a positive screen for alcohol misuse. In conclusion, Soldiers belonging to certain elite combat units are significantly more likely to screen positive for alcohol misuse if they are exposed to specific types of fighting combat experiences versus any other type of combat exposure.