MILD TRAUMATIC BRAIN INJURY (mTBI) appears to be a common condition among US military personnel returning from Iraq and Afghanistan.1,2 Estimates of service members who have either screened positive or been diagnosed with clinician-confirmed mTBI while serving in current conflicts ranges from 11% to 23%.1–5 Work by Terrio et al2 showed that soldiers with clinician-confirmed mTBI were significantly more likely to endorse postconcussive (PC) symptoms (ie, headache, dizziness, balance problems, irritability, and memory problems) after returning from deployment to Iraq (AOR = 5.1, 95% CI = 3.53–7.30, P < .001) than soldiers in the same Brigade Combat Team (BCT) who were injured but did not sustain a TBI. Moreover, when asked to endorse symptoms experienced immediately after injury and at Post Deployment Health Assessment (PDHA), the number of PC symptoms reported by soldiers with TBI decreased over time. Seventy-five percent of individuals reported fewer symptoms postdeployment than at the time of injury.
Postconcussive symptoms are associated with a number of conditions, including depression and posttraumatic stress disorder (PTSD),3,4,6 and attribution to one cause or another can be challenging, particularly if soldiers have co-occurring conditions such as mTBI and PTSD.2–4,7 Further complicating attributional challenges are findings that suggest that: (1) those with TBI are at greater risk for developing PTSD3; and (2) associations exist between premorbid psychiatric and/or personality difficulties and persistent PC symptoms.7–10
Research by Hoge and colleagues3 suggests that the relations among PTSD, mTBI, and PC symptoms are complex. In their cross-sectional survey, mTBI was associated with an increased likelihood of PTSD. Moreover, PC symptoms reported months after injury were more closely associated with PTSD than with mTBI. Hoge et al3 and Bryant11 suggested that attributing PC symptoms to war-related mTBI may have unintended iatrogenic consequences. In addition, Schneiderman et al4 recently found that mTBI (defined as an injury event followed by trouble remembering the injury, a brief loss of consciousness, or self-reported head injury) and PTSD were independently significantly associated with soldier endorsement of 3 or more PC symptoms. Adjusted prevalence ratios for PC symptoms in those with mTBI or PTSD were 1.50 and 3.71, respectively. These findings suggest that although PTSD accounts for PC-like symptoms in some soldiers, mTBI is also independently associated with such symptoms.
One question that has not yet been sufficiently explored is whether having a combination of mTBI and PTSD results in a higher risk of PC symptoms than having either condition alone. In this study our objective was to examine the associations between PC symptoms and mTBI and/or PTSD in soldiers who had recently returned from Iraq. We hypothesized that PTSD and a history of mTBI would each contribute to the endorsement of PC symptoms during PDHA. In addition, we hypothesized that a combination of mTBI and PTSD would be more strongly associated with PC symptoms than having either of those conditions alone.
The study was performed with a retrospective analysis of data from 1247 injured (by self-report) members of a single US Army BCT who returned to Fort Carson, Colorado, from a 1-year deployment in Iraq. All injuries were incurred while serving in Iraq. From a total of 3973 soldiers in the BCT, 2681 denied any injuries acquired in Iraq. Nine hundred and seven of the injured service members had at least 1 clinician-confirmed TBI, and 385 reported an injury history not consistent with TBI. Potential subjects included in the current study included these injured soldiers (n = 1292). All of these soldiers returned from Iraq with their unit as part of the normal rotation of forces and were on full-duty status at the time of the health assessment. As such, soldiers who returned early (eg, medical reasons, left the Army) were not included. In this study, 45 injured soldiers from the BCT who also completed the PDHA were excluded from analyses because of missing demographic and/or PTSD data. As such, the final sample included 1247 soldiers. This BCT and assessment procedures have been previously described in Terrio et al.2
A cross-sectional study design was employed where the exposure, mTBI and/or PTSD, and the outcomes of interest, PC symptoms, were ascertained after soldiers returned from Iraq. These individuals participated in a mandatory postdeployment health evaluation, PDHA. As part of this process, returning military personnel complete a questionnaire designed to gather information about their present health status and war-related exposure to numerous illness-producing risk factors, such as combat stress and environmental hazards (DD Form 2796).12 At Fort Carson, soldiers also completed the Warrior Administered Retrospective Casualty Assessment Tool (WARCAT).13 This questionnaire is based on the Brief Trauma Brain Injury Screen (BTBIS),5 a TBI screening tool found to correlate with clinician assessment in a small sample. WARCAT responses provided information regarding whether a deployed solider was injured from mechanisms commonly associated with TBI, if any injuries resulted in an altered mental status indicative of TBI, and/or if specific somatic and neuropsychiatric symptoms commonly associated with mTBI occurred after the injury (acutely and/or at postdeployment). Endorsed symptoms were not used to make the diagnosis of TBI, but rather to determine the frequency of sequelae. Specific symptoms queried included headaches, dizziness, memory problems, balance problems, and irritability. Items regarding 2 other symptoms, ringing in the ears and sleep problems, were also on the questionnaire, but were not included in the presented analysis because ringing in the ears can result from noise exposure not associated with mTBI and sleep problems often result from recent travel from the war zone to the United States.
After completing the WARCAT, soldiers were interviewed by clinicians. Trained providers asked soldiers to clarify whether an alteration in consciousness in the context of an injury had been sustained.14 The WARCAT and available medical records (eg, from deployment) were reviewed during the interviews with clinicians confirming the details of the injury event (eg, distance from explosives, whether their helmet stayed on, whether others were injured in the incident). Collateral information from battle buddies was obtained and used in the form of a signed affidavit when available. Finally, if during the course of the PDHA evaluation, other injuries were identified that were thought to increase the likelihood that the individual had also sustained a TBI (eg, ruptured eardrums), clinicians asked about a potential combat-related TBI history regardless of the soldier's initial responses on the WARCAT. Clinicians made a final determination of deployment mTBI diagnoses based on their interviews, service members' self-reports, and data gleaned from the medical records and battle buddies. The process did not permit identification of the particular mechanism of injury responsible for the TBI when multiple injuries were sustained in Iraq.
Demographic and military characteristics were obtained from a separate database, Army Medical Surveillance Activity. Four questions from the Defense Department's PDHA survey were used to screen for PTSD. The questions assess 4 dimensions of PTSD (reexperiencing, numbing, avoidance, and hyperarousal).15 Prior research indicates that positive responses on any 2 of the 4 questions had the best combination of sensitivity (79%) and specificity (78%).15 A more complete description of the measure and support for diagnosing PTSD using a 4-item screen can be found in Bliese et al.15 In our study, a positive response on any 2 of the 4 questions was considered indicative of PTSD history.
Univariate and multivariate Poisson regression was used to measure the association between PC symptoms and mTBI alone, PTSD alone, and a combination of the 2 conditions. Multivariate models included age, gender, education military rank, and military occupational specialty (MOS) to adjust for possible confounding. All models were checked for overdispersion.
Of the total 1247 soldiers in the sample, 23% did not have a history of mTBI and screened negative for PTSD, 7% did not have a history of mTBI but screened positive for PTSD, 45% had a history of mTBI but screened negative for PTSD, and 26% had a history of mTBI and screened positive for PTSD (Table 1). Only one demographic characteristic, being 25–29 years old, was associated with increased symptom prevalence (adjusted prevalence ratio = 1.26; 95% confidence interval = 1.02–1.55) (Table 2). No military characteristics were associated with symptom prevalence.
Mild traumatic brain injury alone (adjusted prevalence ratio = 4.03; 95% CI: 2.67–6.07), PTSD alone (adjusted prevalence ratio = 2.74; 95% CI: 1.58–4.74) and both conditions together (adjusted prevalence ratio = 6.27; 95% CI: 4.13–9.43) were significantly associated with a higher prevalence of having any PC symptoms than those without mTBI and PTSD (Table 3). MTBI alone, PTSD alone, and a combination of the two were also each associated with a higher prevalence of headache, dizziness, memory problems, balance problems, and irritability (Table 3). All but three of these associations with a higher prevalence of specific symptoms were statistically significant. The nonsignificant associations were between PTSD alone and dizziness (adjusted prevalence ratio = 4.37; 95% CI: 1.00–19.08), mTBI alone and dizziness (adjusted prevalence ratio = 3.00; 95% CI: 0.92–9.92), and PTSD alone and balance problems (adjusted prevalence ratio = 5.31; 95% CI: 0.91–30.87) (Table 3). A combination of mTBI and PTSD was more strongly associated with a higher prevalence of each specific symptom, as well any symptom, than either condition alone (Table 3).
In this study, mTBI alone (adjusted prevalence ratio = 4.03; 95% CI: 2.67–6.07) and PTSD alone (adjusted prevalence ratio = 2.74; 95% CI: 1.58–4.74) were each associated with a higher prevalence of having any PC symptoms, as well as a higher prevalence of specific symptoms (headache, dizziness, memory problems, balance problems, irritability) among a sample of soldiers returning from deployment in Iraq. In terms of specific symptoms, all but three of these associations were statistically significant.
A combination of mTBI and PTSD was also associated with a higher prevalence of any PC symptom (adjusted prevalence ratio = 6.27; 95% CI: 4.13–9.43) and each of the specific symptoms (Table 3). Furthermore, a combination of mTBI and PTSD was more strongly associated with symptom prevalence than either condition alone. These results support the importance of continued screening for both conditions with the aim of early identification and intervention.
Concerns about unintended iatrogenic consequences resulting from TBI screening may be addressed by providing patients with appropriate information about the natural course of mTBI and its relationship to PC symptoms. Research suggests those who receive early intervention (increased monitoring and education) post-mTBI report fewer symptoms than those who do not receive such augmented care.16 The importance of education regarding the positive expectation of recovery is highlighted by a recent study,17 which found that patient perceptions about the severity and future duration of their PC symptoms early after mTBI were associated with outcome. However, further work is needed to clarify whether or not such interventions are useful months to years after an injury is sustained.
King asserts that if both conditions are present (history of mTBI and PTSD) they can be “mutually exacerbating.”18 This dynamic is commonly seen in a variety of conditions and is known as “psychological factors affecting physical conditions.” Current results supported the additive impact of these 2 conditions on PC symptoms. Education regarding possible symptom combinations (eg, PTSD impacting sleep and subsequent fatigue exacerbating mTBI-related cognitive impairment) and concurrent interventions may be indicated.18 In addition, teaching soldiers about the many potential causes of PC symptoms and highlighting the fact that in some cases the term PC may result in symptom misattribution may be of import. Presented findings support the need for continued exploration of natural histories of both conditions, with particular attention to the potentially additive effect of multidiagnoses upon symptoms. Other factors for consideration include the increased risk for developing PTSD among those with a history of TBI, and the potential impact of individual differences, including genetic factors and/or preexisting psychiatric disorders. A complete discussion regarding the assessment and treatment challenges associated with co-occurring mTBI and PTSD among veterans and military personnel is beyond the scope of this article. Available resources pertaining to this topic are growing and include King18 and Brenner and colleagues.19 Ultimately, additional research aimed at identifying appropriate approaches to assessment and intervention is indicated.
The data analyzed in this report were collected as part of routine clinical care and are archival in nature. Despite inherent limitations, self-report measures are frequently used in the identification and study of PTSD.3,6,15 TBI diagnoses were clinician-confirmed via structured clinical interview, and as such, TBI assessment was potentially more precise than the assessment of PTSD. That is, PTSD determination may have been impacted by the use of a 4-item screening measure.15 Replication of these findings, using a structured clinical interview to confirm PTSD diagnosis, is indicated. Another consideration is that recent research suggests that delayed onset of PTSD is very common (10 months postdeployment).20 Data in this study were collected immediately postdeployment. Findings regarding relationships between PC symptoms, PTSD, and mTBI may change along a longitudinal clinical course. Soldier willingness to endorse symptoms during this mandatory evaluation process may have also impacted results. In addition, all individuals included in the sample had a history of injury not requiring medical evacuation. As a result, reported associations may not be generalizable to soldiers who were not physically injured during their deployment or to those who required more intensive medical or psychiatric treatment. Finally, replication of this study with a control group (soldiers with no history of injury) may increase our understanding regarding relationships between TBI, PTSD, and PC symptoms.
Recent studies asserted that physical health problems associated with deployment are largely attributable to the presence of PTSD.3,4 An association between mTBI and PTSD has also been suggested.3 As such, when mTBI and PTSD are included as separate independent variables in multivariate models while controlling for the other, the effect of mTBI on symptom risk can appear to be statistically nullified. To address this, we separated those with mTBI alone and PTSD alone from those with both conditions. This enabled us to explore the relationship among mTBI, PTSD, and PC symptoms without the confounding effect of the existing association (mTBI and PTSD). Using the above-stated analysis strategy, independent associations between mTBI alone and PTSD alone and increased symptom prevalence were identified. In addition, a combination of the 2 conditions was found to be more strongly associated with higher symptom prevalence than either condition alone. Continued screening for both conditions is supported and further research is required to meet the assessment and treatment needs of returning military personnel.
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Keywords:© 2010 Lippincott Williams & Wilkins, Inc.
Iraq; postconcussive symptoms; PTSD; soldiers; TBI; traumatic brain injury