Brain Injury

ISSN: 0269-9052 (Print) 1362-301X (Online) Journal homepage: http://www.tandfonline.com/loi/ibij20

Characterization of acute stress reaction following an IED blast-related mild traumatic brain injury Jacob N. Norris, Scottie Smith, Erica Harris, David Walter Labrie & Stephen T. Ahlers To cite this article: Jacob N. Norris, Scottie Smith, Erica Harris, David Walter Labrie & Stephen T. Ahlers (2015) Characterization of acute stress reaction following an IED blast-related mild traumatic brain injury, Brain Injury, 29:7-8, 898-904, DOI: 10.3109/02699052.2015.1022879 To link to this article: http://dx.doi.org/10.3109/02699052.2015.1022879

Published online: 08 May 2015.

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Date: 14 November 2015, At: 16:53

http://informahealthcare.com/bij ISSN: 0269-9052 (print), 1362-301X (electronic) Brain Inj, 2015; 29(7–8): 898–904 DOI: 10.3109/02699052.2015.1022879

ORIGINAL ARTICLE

Characterization of acute stress reaction following an IED blast-related mild traumatic brain injury Jacob N. Norris1, Scottie Smith2, Erica Harris3, David Walter Labrie4, & Stephen T. Ahlers5 1

Neurotrauma Department, Naval Medical Research Center, Silver Spring, MD, USA, 2Branch Health Clinic Kings Bay, Kings Bay, GA, USA, Department of Health and Behavioral Sciences, Naval Health Research Center, San Diego, CA, USA, 4Mental Health Department, Naval Medical Center Portsmouth, Portsmouth, VA, USA, and 5Operational and Undersea Medicine Directorate, Naval Medical Research Center, Silver Spring, MD, USA

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3

Abstract

Keywords

Primary objective: To characterize an acute stress reaction (ASR) following an improvised explosive device (IED) blast-related mild traumatic brain injury (mTBI). Research design: Participants were male, US military personnel treated in Afghanistan within 4 days following an IED-related mTBI event (n ¼ 239). Methods and procedures: Demographics, diagnosis of ASR, injury history and self-reported mTBIs, blast exposures and psychological health histories were recorded. Main outcomes and results: In total, 12.5% of patients met ASR criteria. Patients with ASR were significantly younger and junior in rank (p50.05). Patients with ASR were more likely to experience the IED-blast while dismounted, report a loss of consciousness (LOC) and higher pain levels (p50.05). Adjusting for age and rank, multivariate logistic regression showed an association between mTBI history and ASR (AOR ¼ 1.405; 95% CI ¼ 1.105–1.786, p50.01). Adjusting for mechanism of injury (dismounted vs. mounted), LOC and pain, multivariate logistic regression showed an association between mTBI history and ASR (AOR ¼ 1.453; 95% CI ¼ 1.132–1.864, p50.01). Prior blast exposure and past psychological health issues were not associated with ASR. Conclusions: A history of multiple mTBIs is associated with increased risk of ASR. Future research is warranted.

Acute stress reaction, blast, concussion, dismounted, military, multiple mTBIs, psychological health, traumatic brain injury

Introduction In conjunction with a blast-related mild traumatic brain injury (mTBI; also known as a concussion), particularly in the theatre of war, some military service members suffer an acute stress reaction (ASR). In such a setting, immediate symptoms and poor functioning can have dramatic consequences [1]. An ASR is a transient response evident immediately following a traumatic event that usually resolves within 2–3 days. Encompassing a broad range of peri-traumatic responses, ASR can be characterized into four symptom clusters: (1) dissociative symptoms such as numbing or detachment, derealization, dissociative amnesia and/or depersonalization; (2) re-experiencing symptoms such as flashbacks, nightmares or intrusive thoughts; (3) avoidance of stimuli related to the trauma to include thoughts, feelings, people or places; and (4) symptoms of increased anxiety or hyperarousal to include hypervigilance or an exaggerated startle response [1, 2]. Those suffering ASR do not always develop long-term

This article is not subject to US copyright law. Correspondence: LT Jacob N. Norris, Neurotrauma Department, Naval Medical Research Center, 503 Robert Grant Ave, Silver Spring, MD 20910, USA. Tel: (301) 319-7681. Fax: (301) 319-7698. E-mail: [email protected]

History Received 2 July 2014 Revised 15 December 2014 Accepted 6 February 2015 Published online 8 May 2015

psychological health issues and most will recover within a few weeks. However, severe ASRs such as those resulting from combat exposure can result in functional impairments in the near-term that can deteriorate unit cohesion and are associated with longer hospital stays following physical trauma and have reasonable positive predictive power to identify those who will have post-traumatic stress disorder (PTSD) [1, 3, 4]. Persistence of symptoms from all four clusters lasting for more than 2 days and presenting within 4 weeks of a traumatic event indicates an individual meets criteria for acute stress disorder (ASD). When these symptoms are present for longer than 4 weeks or occur more than 4 weeks after the trauma, they meet criteria for PTSD [5]. Although no published research using a military population has evaluated the relationship between mTBI and ASR, a wide body of evidence indicates that mTBI precipitates psychological health problems and impacts daily life in nonmilitary populations. In well-controlled laboratory experiments, rodent models of mTBI have shown that injured rodents demonstrate behaviour consistent with increases in anxiety and poor memory relative to uninjured controls [6–10]. Combat-related mTBI is associated with prolonged post-concussive symptoms (PCS) and PTSD [11]. Broomhall et al. [3] assessed ASR across a broad spectrum of ages and injuries; of those diagnosed with mTBI, 4.62% were

Acute stress reactions after IED mTBI

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diagnosed with ASD vs. 2.47% in the non-mTBI group. The mTBI group had higher levels of behavioural avoidance and subjective distress, which indicated poorer psychological adjustment over the long-term than other groups. Hoge et al. [12], in a survey of redeployed soldiers from Operation Iraqi Freedom (OIF), showed that those with PCS were more likely to endorse symptoms consistent with psychological health disorders on survey scales for depression or PTS. In a retrospective study of returning OIF/OEF (Operation Iraqi Freedom/Operation Enduring Freedom) soldiers, those with mTBI-related post-traumatic headache reported more sick call visits than soldiers without mTBI-related post-traumatic headache [13]. Furthermore, chronic headaches often coexist with other neurobehavioural symptoms. In a cohort of OIF/OEF veterans, 42.1% were simultaneously diagnosed with chronic pain (primarily headaches), PCS and PTSD [14]. Given overlapping symptomologies of ASR and PTSD, along with evidence that mTBI appears to precipitate psychological health issues, it is important to understand ASR in the context of mTBI. Specifically, identifying ASR-associated mTBI symptoms and risk factors for ASR in mTBI patients may lead to targeted early interventions; in non-military populations, evidence suggests early intervention can reduce the odds of developing a psychological health issue like ASD or PTSD. Successful efforts have focused on identifying those most at risk of developing ongoing problems following a traumatic incident and treating them [15]. A systematic review of 15 studies suggested that trauma-focused cognitive behavioural therapy was the most promising early intervention; it was more effective than wait-listing and supportive counselling [16]. Collectively, this evidence indicates that characterizing ASR-associated factors following an mTBI will help identify contributing mechanisms that could lead to improvements in post-mTBI psychological health outcomes. Study aims Building on previous literature and extending research to a military population, the purpose of the current study was to characterize an ASR in personnel who had suffered an mTBI because of an improvised explosive device (IED) detonation and were seen at a US military medical clinic in Afghanistan. The following question was addressed: Would individuals with an ASR be more likely to have a history of psychological health issues or a history of mTBIs? The authors predicted that a history of psychological health issues and a history of mTBIs would be associated with ASRs.

Research design and methods The current study was a retrospective, observational, database record review. The study received approval by the US Army Medical Research and Material Command Institutional Review Board (IRB). The study was granted a waiver of informed consent and followed all required Federal and Defense Department regulations. Participants The target population of this study was military personnel diagnosed with mTBI primary (due to blast wave) and/or

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secondary (hit by objects propelled by the IED) to blast experienced in relation to an IED. If participants were ‘mounted’, that is in or on a vehicle, injury may have resulted in part from platform acceleration injury. Participants were male US military personnel seen within 96 hours of the IED mTBI event (n ¼ 239). The mean age of all patients was 24.3 years old, mid-level enlisted (E4–E6: 56.0%) and junior enlisted (E1–E3: 39.7%) from the Marine Corps (74.1%) and the Army (23.8%). The soldiers were primarily from infantry (27.2%), convoy operations (24.6%) and combat engineering/ engineering (22.2%) occupational specialties. There were no females included in this study. Psychological health, mTBI and blast exposure history Self-reported histories of psychological health problems were collected at initial intake. Responses were recorded as ‘yes/ no’, with no further differentiation for type of psychological health problem. Patients were asked if they had any mTBIs previous to the current IED-related injury. If they reported that they had an mTBI, then they were asked to explain the mechanism of injury for each mTBI and give an approximate date. They were also asked if the mTBI was related to combat. In this study, no ASR patients reported combat-related mTBIs and only four non-ASR patients reported a previous combatrelated mTBI. Therefore, combat and non-combat related mTBIs were collapsed together. Patients were asked to report the number of instances they recalled when they were within a 50-metre radius of a blast or an explosion within the last year (prior to the index event). Pain scale As part of intake, patients were asked to assess their pain level on a scale of 0–10. Patients were instructed that 0 was equivalent to no pain, 5 was equivalent to moderate pain and 10 was equivalent to the worst pain possibly imaginable. mTBI diagnosis and classification Diagnosis and classification of mTBI was determined by a residency-trained family medicine physician with training in mTBI assessment. The clinicians categorized patients as having a concussion with loss of consciousness (LOC), concussion without LOC or no concussion. A mTBI was defined as a traumatic brain injury having normal structural imaging (if imaging is performed), LOC of no more than 30 minutes and/or alteration of consciousness or post-traumatic amnesia of no more than 24 hours. Alteration of consciousness was defined as mental status alteration immediately that was related to the event. The patient may have reported looking and feeling dazed, uncertain of what was happening, being confused, having difficulty thinking clearly or being unable to describe events immediately before or after the trauma event [17]. Commonly this was described by patients as getting their ‘bell rung’ or ‘seeing stars’. If the patient reported a period of loss of postural tone and unconsciousness immediately after the blast, followed by a period of confusion, stupor and/or disorientation, then they were considered to have experienced a LOC.

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Acute stress reaction (ASR) As part of routine clinical care, residency-trained family medicine physicians assessed patients for ASR using established criteria [1, 2]. It was the noted presence of (1) dissociative symptoms, (2) re-experiencing symptoms, (3) avoidance and (4) symptoms of increased anxiety or hyper arousal. Those with an ASR were referred for follow-up evaluation and treatment with a licensed clinical psychologist or psychiatrist. Referrals, including the reason for referral placement, were noted in the database. Providers assessed for psychological health issues through clinical interview. ASR was defined consistent with DoD Directive 6490.5 [18] as the ‘expected, predictable, emotional, intellectual, physical and/or behavioural reactions of service members who have been exposed to stressful events [either] in combat or military operations other than war’ (p 8). Such reactions are normal in the war environment and persons suffering from an ASR are typically otherwise healthy patients [19]. There are six categories of acute/combat stress including physical, cognitive, behavioural, emotional, misconduct and adaptive [19]. Variables and statistical analysis For the purposes of the study, the main outcome measure was an ASR. An ASR was defined as presentation of symptoms meeting ASR criteria or a documented ASR in the clinic database. In addition to being examined by a family trained physician, all cases were reviewed by a clinical or research psychologist. First, cases were screened for presence of ASR documentation or a referral for a suspected ASR. Then those cases were screened in order to verify they met ASR criteria. Other variables included self-reported mTBI history and demographics via clinical intake. Microsoft Office Excel and Access 2007 were used to process data. Analyses were conducted on Microsoft Office Excel 2007, SPSS 21.0 (IBM Inc., 2013, Pittsburgh, PA, USA) and StatView (SAS Inc., 1992–1998, Cary, NC, USA) software. Descriptive statistics, Student’s t-test (equal variances not assumed), Pearson’s Chi-

Brain Inj, 2015; 29(7–8): 898–904

square, Fisher’s Exact Test and logistic regression were conducted. In order to reduce the influence of outliers in the logistic regression, the number of blast exposures and mTBIs were transformed into rank order variables with ties allowed. Statistical significance was set to p  0.05 for all analyses.

Results All patients were male and had sustained an IED blast-related mTBI within the previous 4 days. Of the 239 participants who met criteria for inclusion, 30 patients (12.5%) were determined to have an ASR. Demographics and participant characteristics are in Table I. There were some demographic differences between those with ASR and those without ASR. Those with ASRs were younger (M ¼ 22.9 years old, SD ¼ 3.1) than those without ASR (M ¼ 24.6 years old, SD ¼ 4.4). This was confirmed using a Student’s t-test, t(47.859) ¼ 2.578, p50.05. Using a Pearson’s Chi-square test, those with ASR were demonstrated to be significantly junior enlisted in rank (60.0% vs. 36.8%, 2 ¼ 6.554, p50.05). There were injury differences between those with ASR and those without ASR. Those with ASR were significantly more likely to have been injured while dismounted (30.0% vs. 13.8%, 2 ¼ 3.971, p50.05) and to report a LOC following the event (53.3% vs. 28.7%, 2 ¼ 6.248, p50.05). Reported pain levels were greater among those with an ASR (M ¼ 5.0, SD ¼ 1.8) than those without an ASR (M ¼ 3.9, SD ¼ 2.2). This was confirmed with a Student’s t-test, t(234) ¼ 2.686, p50.01. Factors associated with ASR In the overall sample, 5.0% of patients reported a history of psychological health problems. Among ASR patients, 6.7% reported a history of psychological health problems. Among non-ASR patients, 4.7% reported a history of psychological health problems. The mean number of prior mTBIs was 0.745 (SD ¼ 1.43). The number of previous lifetime mTBIs ranged from 0–11.

Table I. Demographics and participant characteristics (n ¼ 239). ASR (n ¼ 30) n Mean age (years) ± SD Mean reported pain levels (1–10) ± SD Rank Junior enlisted (E1–E3) Middle enlisted (E4–E6) Senior enlisted/Officer (E7–O7) Mechanism of IED injury (dismounted, i.e. on foot) Reported loss of consciousness following IED mTBI (Yes) Prior psychological health issues # Prior mTBIs Zero One More than one # Blast bxposures in last 12 months Zero One More than one

%

22.9 ± 3.1 5.0 ± 1.8

No ASR (n ¼ 209) n

%

24.6 ± 4.4 3.9 ± 2.2

18 12 0 9 16 2

60.0 40.0 0.0 30.0 53.3 6.7

77 122 10 29 60 10

36.8 58.7 4.5 13.8 28.7 4.7

16 6 8

53.3 20.0 26.7

136 40 33

65.1 19.1 15.7

14 6 10

46.7 20.0 33.3

104 53 52

49.8 25.3 24.9

ASR, Acute Stress Reaction; mTBI, mild traumatic brain injury; SD, standard deviation; IED, improvised explosive device.

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Table II. Unadjusted and adjusted odds ratio of being screened positive for an acute stress reaction (n ¼ 239). Unadjusted Potential factor Prior psychological health issues Number of reported lifetime mTBIs Number of reported blast exposures within 12 months

Adjusted for demographics

Adjusted for injury differences

OR

95% CI

AOR

95% CI

AOR

95% CI

1.421 1.358 1.008

0.296–6.826 1.075–1.716* 0.783–1.299

1.876 1.405 1.013

0.369–9.529 1.105–1.786** 0.788–1.302

1.460 1.453 0.970

0.282–7.553 1.132–1.864** 0.751–1.251

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*p50.05, **p50.01. OR, odds ratio; AOR, adjusted odds ratio; CI, confidence intervals; mTBI, mild traumatic brain injury; Multivariate analyses (Adjusted) controlled for demographics (age and rank) and injury (reported pain levels, reported loss of consciousness and mechanism of injury); Number of mTBIs and Blast Exposures were converted to rank order (with ties allowed) to reduce influence of outlier values.

Among ASR patients, 53.3% reported no mTBIs before the single IED-related mTBI, 20% reported a single mTBI before the IED-related mTBI and 26.7% reported multiple mTBIs before the IED-related mTBI. With non-ASR patients, 65.1% reported no mTBI before the single IED-related mTBI, 19.1% reported a single mTBI before the IED-related mTBI and 15.7% reported multiple mTBIs before the IED-related mTBI. In the preceding year, the mean number of blast exposures was 1.067 (SD ¼ 1.586) and ranged between 0–10. In ASR patients, 46.7% reported no blast prior exposures, 20% reported a single previous blast exposure and 33.3% reported multiple previous blast exposures. Among non-ASR patients, 49.8% reported no prior blast exposures, 25.3% reported a single mTBI before the IED-related mTBI and 24.9% reported multiple mTBIs before the IED-related mTBI. Univariate (unadjusted) and multivariate (adjusted) logistic regression models evaluating psychological health, mTBI history and blast exposure history with a positive ASR screen as the dichotomous outcome variable are presented in Table II [20]. Univariate analysis showed a relationship between the number of mTBIs and ASR (OR ¼ 1.358; 95% CI ¼ 1.075– 1.716, p50.05). The first set of multivariate logistic regression analyses controlled for demographic differences. Adjusting for age and rank, multivariate logistic regression showed a similar association between mTBI and ASR (AOR ¼ 1.405; 95% CI ¼ 1.105–1.786, p50.01). The second set of multivariate analysis controlled for injury differences. Adjusting for mechanism of injury (dismounted vs. mounted), reported LOC and pain levels, the second multivariate logistic regression showed a similar association between mTBI and ASR (AOR ¼ 1.453; 95% CI ¼ 1.132–1.864, p50.01). After adjusting for all covariates, results indicate with each additional prior mTBI the average probability of developing an ASR increases by 1.4 times.

Discussion The purpose of this study was to characterize ASR following an IED-related concussion specifically if psychological health history, mTBI history or blast exposure history were associated with an ASR. This study evaluated the results of patient screening for an ASR in a combat setting based on the rationale that those with an ASR would present to clinicians with different histories than those without ASR. Overall, results supported the general rationale and hypotheses. After controlling for both demographic and injury differences,

analyses showed for each reported prior mTBI, patients were on average 1.4 times more likely to experience an ASR. Similar analyses showed that a history of blast exposure and psychological health issues were not associated with an ASR. Factors associated with ASR Those with an ASR were more likely to report a history of multiple mTBIs in their lifetime. For each mTBI sustained, the probability of developing an ASR was 1.4 times greater. For example, in an individual with at least three mTBIs, this translates to an average of 4.2 times increase in the probability of developing an ASR. Research from a variety of settings indicates that a history of head injury increases susceptibility to future injury and is related to poor neuropsychological and emotional outcomes. Statistically, athletes with prior mTBIs are at increased risk for a future mTBI [21–24]. Other research has shown that athletes with three-or-more previous mTBIs performed worse on verbal memory tests than athletes with fewer mTBIs [25, 26]. In adolescents, collegiate athletes and retired professional American football players, a history of concussion was associated with increased risk of depression [27–29]. In a sample of military deployed to Iraq, depression, PTSD and suicidal thoughts increased with the number of TBIs [30]. However, other research has shown evidence that one or two previous mTBIs does not affect recovery on neuropsychological testing or symptom reporting [31, 32]. As such, the results do not advocate that any specific number of mTBIs can be adopted as a critical threshold. Results only suggest that for each mTBI ASR susceptibility may increase by 1.5 times. Of importance is the finding that patients with an ASR did not report a history of combat-related mTBIs. While the evidence indicating that a history of mTBI-like events leads to decreased psychological function or increased anxiety, it does not dictate that head trauma must coincide with a stressor; it is reasonable to have assumed a priori that history of mTBI in combination with combat should have increased the likelihood of an ASR. Collectively, this indicates the number of mTBIs, rather than circumstances of past mTBIs (combat vs. non-combat) may be a crucial factor in determining susceptibility to psychological health problems following a single blast-related mTBI. Alternatively, lack of association between multiple combat mTBIs and ASR may have been the result of low occurrence of previous combatrelated mTBI. A low rate of historical combat-related mTBI in the sample may be a reflection of recent DoD rules

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restricting those with multiple combat-related mTBIs from combat operations. In addition to the findings concerning mTBI history, there were demographic differences between the two groups. Those with an ASR tended to be younger and more junior in rank than to those without an ASR. These findings were consistent with the literature. It is known that in civilian populations a variety of factors impact recovery from mTBI and the development of an ASR [8, 33–36]. Meta-analysis shows that younger age may also be a risk factor for an ASR [37]. Evidence from emergency room settings suggests that assaultive trauma and low socioeconomic status may be more prevalent in younger people, thereby accounting for the age factor [38]. It is also possible that youth was associated with ASR because older personnel may have had more life experience that would allow them to handle the trauma of an IED event. However, this study did not record lifetime combat history, so this is speculation at best. Second, those with ASR were more likely dismounted as opposed to mounted when they sustained a concussion. IED detonations may be more traumatizing when personnel are dismounted than when personnel are mounted. Third, those with an ASR were more likely to have sustained an LOC following the IED-event. This may further be an indicator that those with an ASR suffered more severe mTBI, as LOC has been used as an indicator of concussion severity in civilian settings [33, 39–46]. Finally, those with an ASR reported greater pain levels than those without ASR. This is consistent with evidence from paediatric TBI patients [47]. Appropriately, these factors were controlled as covariates in the multivariate logistic regression. Not all expected elements of health and mTBI history were associated with ASR. It is expected that self-reported history of psychological health issues would have been associated with experiencing an ASR. Evidence from civilian settings indicates that a history of previous mental health problems was a strong predictor of psychological distress following admission to an emergency room [48, 49]. This prediction was consistent with recent evidence showing severity of the ASR may be predicted by an individual’s increase in trait anxiety, suicidal risk and post-traumatic cognitions [50]. The current study may have different results due to restriction of the sample range; those with severe psychological health issues would be less likely to deploy. Alternatively, low rates of psychological health issues could have resulted from how providers asked questions about past psychological health. Perhaps questions were poorly worded or confusing. It had also been expected that blast exposure history would be associated with ASR. Although the exact dose/response relationship between blast over-pressure and mTBI is still unknown, evidence suggests that repeated sub-clinical exposure may cause disruption of neurological function such that an individual would be at increased risk of ASR. Results in the current study may have been due to relatively low rates of blast exposure. In experienced boxers, increased total number of professional bouts was associated with poorer memory performance [51]. Although this study was observational and only evaluated persons following a diagnosed IED-related mTBI, this study suggests that a history of physical trauma resulting in mTBI

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may pre-dispose an individual to psychological issues. In this study, because LOC and prior mTBI were associated with ASR, one could argue for the role of physical trauma as the driver of persistent neurobehavioural health issues, rather than the psychological stressors as preferred by Hoge et al. [12]. However, given the study’s observational design, one should not interpret this work as definitive. The issue of separating health issues resulting from mTBI and those resulting from psychological trauma remains a challenge for the research and clinical communities. In order to have properly addressed this question, one needs sufficient access to participants who sustained combat-related non-blast mTBI and participants who experienced an IED event but did not sustain a mTBI. Limitations The primary limitations of this study were the cross-sectional design element and self-reported information from a convenience sample. The cross-sectional design prevented researchers from being able to truly evaluate risk. Patients were screened for ASR shortly after reporting symptoms. Results were necessarily limited to the identification of significant associations between potential risk factors and probable outcomes. As a convenience sample made of patients that were seen at a specialty clinic, the patients might have had more severe uncomplicated mTBI than the general uncomplicated mTBI population. Because of the sample composition, some subgroups were relatively small; therefore, it is prudent to temper inference and call for further research. Finally, future research should gather similar information on non-mTBI patients exposed to blast and mTBI patients with injuries resulting from non-blast combat mechanisms. This would allow for researchers to answer more questions concerning ASR and mTBI in military samples. Self-reported information from a convenience sample may also result in a collection of biased information from patients who felt that under-reporting symptoms would ensure they could speedily return to their daily duties. Patients may also under-report health issues and/or the number of blast exposures they have had in the hopes of returning to small forward operating bases and to their units to continue to engage. Patients could have also under-reported blast or mTBI history due to memory lapses or misunderstanding the content of the questions asked to them. Alternatively, these service members may have over-reported health issues to avoid returning to remote forward operating bases and likely re-traumatization. In a related way, as this was a convenience sample, some information such as combat exposure was not collected. Those with an ASR may have experienced greater or longer combat than those without an ASR. As always, self-reported data are vulnerable to distortion. Future directions Because the current study used a relatively homogenous sample for age and socioeconomic status, more research is needed to fully evaluate the effect of age and sex on psychological health and mTBI [52–54]. Future efforts should extend this knowledge to combat settings, especially as it relates to psychological health issues following mTBI.

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Other factors to consider include deployment and unit-related or inter-personal factors [9, 19, 55]. A variety of environmental stressors including living conditions, weather, peer-to-peer relationships, supervisor relationships, poor sleep and possible sexual or physical abuse could have played a role. Unit cohesion (morale) or use of a coping strategy could provide a protective benefit against psychological health problems following mTBI [5, 19, 54]. Another direction would be to examine in this population whether ASR is predictive of persistent neurobehavioural issues such as PCS or PTSD.

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Conclusion This study represents an appreciable advance in the understanding of ASR in conjunction with an mTBI and may facilitate prudent allocation of resources towards those with elevated risk to develop such issues. Increased knowledge in this arena may lead to improved psychological ‘triage’ or targeted cognitive behavioural therapy for those at greatest risk of later psychological health issues. To the authors’ knowledge, this is the first study to evaluate whether health history was associated with the development of an ASR. On a basic level, this study suggests that a history of mTBI may pre-dispose an individual to psychological issues. Unlike providers in stateside or civilian settings, in-theatre combat medical professionals must assess personnel for their suitability to survive in a highly variable combat setting. Because the effects of psychological injury can remain undetected, some personnel fail to receive necessary additional care. This study suggests that, by inquiring about mTBI history, clinicians and frontline providers can improve psychological health screening among service members who might be at increased risk of developing an ASR.

Acknowledgments The authors would like to thank Dr Richard McCarron and Ms Alexis Gage for editorial review and Dr Ashraful Haque for feedback on earlier drafts of the manuscript.

Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper. This report was supported by the Navy Bureau of Medicine and Surgery under Work Units No. N24LB. The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense or the US Government. Approved for public release; distribution is unlimited. This research has been conducted in compliance with all applicable federal regulations governing the protection of human subjects in research (USAMRMC IRB Number M10166 and NMRC.2013.0003). CDR Labrie, LT Knox, LT Norris and LT Harris are military service members. This work was prepared as part of their official duties. Title 17 U.S.C. x 105 provides that ‘Copryight protection under this title is not available for any work of the United States Government’. Title 17 U.S.C. x 101 defines a US Government work as a work prepared by a military service member or employee of the US Government as part of that person’s official duties.

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References 1. Isserlin L, Zerach G, Solomon Z. Acute stress responses: A review and synthesis of ASD, ASR, and CSR. The American Journal of Orthopsychiatry 2008;78:423–429. 2. WHO. World Health Organization, ICD-10: The ICD-10 classification of mental and behavioural disorders: Clinical descriptions and diagnostic guidelines. Geneva, Switzerland: World Health Organization; 1992. 3. Broomhall LG, Clark CR, McFarlane AC, O’Donnell M, Bryant R, Creamer M, Silove D. Early stage assessment and course of acute stress disorder after mild traumatic brain injury. The Journal of Nervous and Mental Disease 2009;197:178–181. 4. Bryant RA. Acute stress disorder as a predictor of posttraumatic stress disorder: A systematic review. Journal of Clinical Psychiatry 2011;72:233–239. 5. APA. Diagnostic and statistical manual for mental disorders. 5th ed. Washington, DC: The American Psychiatric Association; 2013. 6. Ahlers ST, Vasserman-Stokes E, Shaughness MC, Hall AA, Shear DA, Chavko M, McCarron RM, Stone JR. Assessment of the effects of acute and repeated exposure to blast overpressure in rodents: Toward a greater understanding of blast and the potential ramifications for injury in humans exposed to blast. Frontiers in Neurology 2012;3:1–12. 7. Elder GA, Dorr NP, De Gasperi R, Gama Sosa MA, Shaughness MC, Maudlin-Jeronimo E, Hall AA, McCarron RM, Ahlers ST. Blast exposure induces post-traumatic stress disorder-related traits in a rat model of mild traumatic brain injury. Journal of Neurotrauma 2012;29:2564–2575. 8. Kamnaksh A, Kovesdi E, Kwon SK, Wingo D, Ahmed F, Grunberg NE, Long J, Agoston DV. Factors affecting blast traumatic brain injury. Journal of Neurotrauma 2011;28:2145–2153. 9. Meyer DL, Davies DR, Barr JL, Manzerra P, Forster GL. Mild traumatic brain injury in the rat alters neuronal number in the limbic system and increases conditioned fear and anxiety-like behaviors. Experimental Neurology 2012;235:574–587. 10. Reger ML, Poulos AM, Buen F, Giza CC, Hovda DA, Fanselow MS. Concussive brain injury enhances fear learning and excitatory processes in the amygdala. Biological Psychiatry 2012;71: 335–343. 11. Ruff RL, Riechers RG, Ruff SS. Relationships between mild traumatic brain injury sustained in combat and post-traumatic stress disorder. F1000 Medicine Reports 2010;2:64. 12. Hoge CW, McGurk D, Thomas JL, Cox AL, Engel CC, Castro CA. Mild traumatic brain injury in U.S. Soldiers returning from Iraq. The New England Journal of Medicine 2008;358:453–463. 13. Theeler BJ, Flynn FG, Erickson JC. Headaches after concussion in US soldiers returning from Iraq or Afghanistan. Headache 2010;50: 1262–1272. 14. Lew HL, Otis JD, Tun C, Kerns RD, Clark ME, Cifu DX. Prevalence of chronic pain, posttraumatic stress disorder, and persistent postconcussive symptoms in OIF/OEF veterans: Polytrauma clinical triad. Journal of Rehabiliation, Research and Development 2009;46:697–702. 15. Brewin CR, Scragg P, Robertson M, Thompson M, d’Ardenne P, Ehlers A, Psychosocial Steering Group LBTRP. Promoting mental health following the London bombings: A screen and treat approach. Journal of Traumatic Stress 2008;21:3–8. 16. Roberts NP, Kitchiner NJ, Kenardy J, Bisson JI. Early psychological interventions to treat acute traumatic stress symptoms. Cochrane Database of Systematic Reviews 2010;3:CD007944. 17. Conaton E. DoD policy guidance for management of mild traumatic brain injury/concussion in the deployed setting (DoD Instruction [DoDI] Number 6490.11). In: Defense Do, editor. Washington, DC: Department of Defense; 2012. 18. Hamre JJ. Department of Defense Directive Number 6490.5. Defense, D.o., editor. Washington, DC: Department of Defense; 2003. 19. Campise RL, Geller SK, Campise ME. Combat stress. New York, NY: The Guilford Press; 2003. 20. Portney LG, Watkins MP. Foundations of clinical research: Applications to practice. 3rd ed. Upper Saddle, NJ: Pearson Education, Inc.; 2009. 21. Delaney JS, Lacroix VJ, Leclerc S, Johnston KM. Concussions during the 1997 Canadian Football League season. Clinical Journal

904

22.

23.

24.

Downloaded by [University of Wisconsin Oshkosh] at 16:53 14 November 2015

25.

26. 27. 28.

29.

30. 31.

32.

33.

34.

35.

36.

37.

J. N. Norris et al. of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine 2000;10:9–14. Gerberich SG, Priest JD, Boen JR, Straub CP, Maxwell RE. Concussion incidences and severity in secondary school varsity football players. American Journal of Public Health 1983;73: 1370–1375. Guskiewicz KM, McCrea M, Marshall SW, Cantu RC, Randolph C, Barr W, Onate JA, Kelly JP. Cumulative effects associated with recurrent concussion in collegiate football players: The NCAA Concussion Study. JAMA: The Journal of the American Medical Association 2003;290:2549–2555. Zemper ED. Two-year prospective study of relative risk of a second cerebral concussion. American Journal of Physical Medicine & Rehabilitation/Association of Academic Physiatrists 2003;82: 653–659. Collins MW, Iverson GL, Lovell MR, McKeag DB, Norwig J, Maroon J. On-field predictors of neuropsychological and symptom deficit following sports-related concussion. Clinical Journal of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine 2003;13:222–229. Iverson GL, Brooks BL, Lovell MR, Collins MW. No cumulative effects for one or two previous concussions. British Journal of Sports Medicine 2006;40:72–75. Chrisman SP, Richardson LP. Prevalence of diagnosed depression in adolescents with history of concussion. Journal of Adolescent Health 2014;54:582–586. Kontos AP, Covassin T, Elbin RJ, Parker T. Depression and neurocognitive performance after concussion among male and female high school and collegiate athletes. Archives of Physical Medicine & Rehabilitation 2012;93:1751–1756. Guskiewicz KM, Marshall SW, Bailes J, McCrea M, Harding Jr HP, Matthews A, Mihalik JR, Cantu RC. Recurrent concussion and risk of depression in retired professional football players. Medicine & Science in Sports & Exercise 2007;39:903–909. Bryan CJ, Clemans TA. Repetitive traumatic brain injury, psychological symptoms, and suicide risk in a clinical sample of deployed military personnel. JAMA Psychiatry 2013;70:686–691. Iverson GL, Echemendia RJ, Lamarre AK, Brooks BL, Gaetz MB. Possible lingering effects of multiple past concussions. Rehabilitation Research and Practice 2012, Article ID 316575, doi:10.1155/2012/316575. Lowe M, Harris W, Kane RL, Banderet L, Levinson D, Reeves D. Neuropsychological assessment in extreme environments. Archives of Clinical Neuropsychology: The Official Journal of the National Academy of Neuropsychologists 2007;22:S89–S99. Asplund CA, McKeag DB, Olsen CH. Sport-related concussion: Factors associated with prolonged return to play. Clinical Journal of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine 2004;14:339–343. Collins M, Lovell MR, Iverson GL, Ide T, Maroon J. Examining concussion rates and return to play in high school football players wearing newer helmet technology: A three-year prospective cohort study. Neurosurgery 2006;58:275–286; discussion 275–286. Faux S, Sheedy J, Delaney R, Riopelle R. Emergency department prediction of post-concussive syndrome following mild traumatic brain injury–an international cross-validation study. Brain Injury 2011;25:14–22. Sheedy J, Harvey E, Faux S, Geffen G, Shores EA. Emergency department assessment of mild traumatic brain injury and the prediction of postconcussive symptoms: A 3-month prospective study. Journal of Head Trauma Rehabilitation 2009;24:333–343. Brewin CR, Andrews B, Valentine JD. Meta-analysis of risk factors for posttraumatic stress disorder in trauma-exposed adults. Journal of Consulting and Clinical Psychology 2000;68:748–766.

Brain Inj, 2015; 29(7–8): 898–904

38. Alarcon LH, Germain A, Clontz AS, Roach E, Nicholas DH, Zenati MS, Peitzman AB, Sperry JL. Predictors of acute posttraumatic stress disorder symptoms following civilian trauma: Highest incidence and severity of symptoms after assault. The Journal of Trauma and Acute Care Surgery 2012;72:629–635; discussion 635–627. 39. Iverson G. Predicting slow recovery from sport-related concussion: The new simple-complex distinction. Clinical Journal of Sport Medicine 2007;17:31–37. 40. Lau BC, Kontos AP, Collins MW, Mucha A, Lovell MR. Which onfield signs/symptoms predict protracted recovery from sportrelated concussion among high school football players? American Journal of Sports Medicine 2011;39:2311–2318. 41. Kelly JP. Loss of Consciousness: Pathophysiology and implications in grading and safe return to play. Journal of Athletic Training 2001;36:249–252. 42. Kelly JP, Rosenberg JH. The development of guidelines for the management of concussion in sports. Journal of Head Trauma Rehabilitation 1998;13:53–65. 43. Torg JS. Athletic injuries to the head, neck and face. 2nd ed. Philadelphia, PA: Lea & Febiger; 1982. 44. Cunningham J, Brison RJ, Pickett W. Concussive symptoms in emergency department patients diagnosed with minor head injury. Journal of Emergency Medicine 2011;40:262–266. 45. Erlanger D, Kaushik T, Cantu R, Barth JT, Broshek DK, Freeman JR, Webbe FM. Symptom-based assessment of the severity of a concussion. Journal of Neurosurgery 2003;98:477–484. 46. Hoffman JM, Lucas S, Dikmen S, Braden CA, Brown AW, Brunner R, Diaz-Arrastia R, Walker WC, Watanabe TK, Bell KR. Natural history of headache after traumatic brain injury. Journal of Neurotrauma 2011;28:1719–1725. 47. Brown EA, Kenardy JA, Dow BL. TSD Perpetuates pain in children with traumatic brain injury. Journal of Pediatric Psychology 2014; 39:512–520. 48. Mason S, Turpin G, Woods D, Wardrope J, Rowlands A. Risk factors for psychological distress following injury. British Journal of Clinical Psychology 2006;45:217–230. 49. Mason S, Farrow TF, Fawbert D, Smith R, Bath PA, Hunter M, Woodruff PW, Turpin G. The development of a clinically useful tool for predicting the development of psychological disorder following injury. British Journal of Clinical Psychology 2009;48: 31–45. 50. Suliman S, Troeman Z, Stein DJ, Seedat S. Predictors of acute stress disorder severity. Journal of Affective Disorders 2013;149: 277–281. 51. Ravdin LD, Barr WB, Jordan B, Lathan WE, Relkin NR. Assessment of cognitive recovery following sports related head trauma in boxers. Clinical Journal of Sport Medicine: Official Journal of the Canadian Academy of Sport Medicine 2013;13: 21–27. 52. Dick RW. Is there a gender difference in concussion incidence and outcomes? British Journal of Sports Medicine 2009;43:i46–i50. 53. Field M, Collins MW, Lovell MR, Maroon J. Does age play a role in recovery from sports-related concussion? A comparison of high school and collegiate athletes. The Journal of Pediatrics 2003;142: 546–553. 54. Turner MA, Kiernan MD, McKechanie AG, Finch PJ, McManus FB, Neal LA. Acute military psychiatric casualties from the war in Iraq. The British Journal of Psychiatry: The Journal of Mental Science 2005;186:476–479. 55. Rundell JR. Demographics of and diagnoses in Operation Enduring Freedom and Operation Iraqi Freedom personnel who were psychiatrically evacuated from the theater of operations. General Hospital Psychiatry 2006;28:352–356.