SEVERAL RECENT SURVEY reported that a substantial minority of military personnel returning from Iraq and Afghanistan have screened positive for having experienced a mild traumatic brain injury (mTBI) during deployment (eg, 11.2%–22.8%).1,2–5 The majority of published studies to date have been based on postdeployment surveys—relatively few have involved medically evacuated individuals with multiple bodily injuries. Combat-related injuries resulting in medical evacuation may be serious, life threatening, or both as well as psychologically traumatic. Service members who are wounded in combat, whether medically evacuated or treated in-theater, are at increased risk for posttraumatic stress disorder (PTSD),6 depression,7 and/or chronic pain.8 These comorbidities can make it challenging to determine if a service member does or does not suffer from residual symptoms associated with an mTBI.
In the current military conflicts, explosions are the most common mechanism of injury, accounting for 78% of all injuries, the highest proportion seen in any large-scale conflict, while gunshot wounds accounted for only 18% of the injuries.9 Blast as a mechanism of injury has some unique characteristics, such as more frequent injuries to the face (with associated visual, hearing, and vestibular impairment) and greater symptoms of posttraumatic stress.10 In a Veterans Affairs polytrauma sample, service members injured by blast had a broader spectrum of physical injuries, higher levels of admission and discharge opioid analgesic use, greater pain following treatment, and much higher rates of PTSD and other psychiatric diagnoses than those injured via motor vehicle collisions, falls, or other mechanisms.11 This has also been observed in civilian victims of terror attacks, with those injured in blasts having more injured body regions, and being more severely injured overall, than those injured through other mechanisms.12
Assessing outcome from an mTBI in service members with multiple bodily injuries is difficult and complicated for multiple reasons. First, researchers have reported that orthopedically-injured patients with no head trauma report symptoms and problems that are postconcussion-like at 1 week,13 3 months, and 12 months14 following injury. It is well established in the literature that chronic pain is associated with symptoms typical of a postconcussion syndrome.15–21 Chronic widespread pain has been reported frequently in a sample of OIF and OEF veterans and has been shown to be related to worse physical role function independent of comorbid mental health concerns.22
Second, researchers have reported that more than 30% of civilians who experience polytrauma have a diagnosable mental health problem in the first year after injury.23 Like chronic pain, mental health problems can mimic or mask residual symptoms of mTBI. Postconcussion-like symptoms are common in individuals with depression24 and PTSD.25 In a veteran population screening positive for mTBI, posttraumatic stress accounted for a statistically significant amount of variance with every postconcussive symptom reported. This was not restricted to typically “emotional” symptoms, because 5% to 13% of the variance in somatic and sensory symptoms was also accounted for by posttraumatic stress.26
Third, in a civilian study, the odds for return to work 6 months after injury were 3.4 times greater in patients with isolated mTBIs than in patients that suffered additional bodily injuries. The absence of pain shortly after injury was associated with a 2.3 greater likelihood of favorable outcome.27 These authors concluded that accurate prediction of outcome required an understanding of factors other than injury to the head and brain. This is consistent with previous work28 indicating that the presence of bodily injuries was associated with lower levels of physical functioning, lower return-to-work rates, and worse global outcome 6 months after trauma.
Therefore, intuitively, more extensive combat-related physical injuries might be associated with increased risk for chronic pain, mental health problems, or both during the recovery process. During the initial weeks and months, symptoms and problems associated with physical injuries, psychological distress, and mTBI can be additive, overlapping, and interwoven. Thus, it is important to systematically study the relations among physical injury, pain, psychological distress, and postconcussion symptoms. A recent study of civilian polytrauma cases, by Bryant and colleagues (2010), illustrated that (a) new onset mental health problems occur in a substantial minority of civilians hospitalized for polytrauma (>20%), (b) new-onset mental health problems were slightly more prevalent in polytrauma cases with co-occurring mTBIs, and (c) those classified as having moderate or severe bodily injuries had somewhat higher rates of mental health problems than those classified as having mild or critical injuries (as defined by the Abbreviated Injury Scale [AIS]). On the contrary, a recent study by Kennedy and colleagues29 examined whether the presence of a physical injury (besides the mTBI itself) affected postconcussion or traumatic stress symptom reporting in a combat-injured mTBI sample. These authors concluded that other bodily injuries might be at least partially protective against the development of stress and neurobehavioral symptoms in service members who sustained an mTBI. The purpose of this study is to expand on the work by Kennedy and colleagues by examining the relations among more severe bodily injuries, traumatic stress, and postconcussion symptoms in a sample of combat-injured service members who sustained mTBIs.
Given the contradictory findings in the literature regarding bodily injury and symptom reporting, this study was considered exploratory in nature and no a priori hypotheses were proposed.
Participants were 137 patients who sustained an uncomplicated mTBI and were evaluated at the Walter Reed Army Medical Center (WRAMC), Washington, DC, following medical evacuation from the OIE/OEF combat theater for their injuries. Patients were selected from a larger sample of 571 US military service members who were evaluated at WRAMC between December 2005 and May 2008 following a suspected or confirmed TBI sustained during OEF/OIF, and who had agreed to the use of their clinical data for research purposes. All participants had sustained multiple bodily injuries that ranged from minor (12.4%), moderate (35.0%), serious (29.2%), severe (19.7%) to critical (3.6%; based on a modified Injury Severity Score (ISS) from the AIS—see the “Measures and Procedures” section below). As a general rule, patients were primarily medically evacuated for limb loss or systemic injuries, rather than mTBI per se.
Patients were included in the selected sample if they (a) had sustained a closed TBI (n = 544, 95.3% of total sample), (b) had sufficient information available that could be used to confidently classify them as having sustained an uncomplicated mTBI (n = 299, 52.4% of total sample), (c) were male (n = 538, 94.2% of total sample), (d) were wounded in OEF/OIF (n = 503, 88.1% of total sample), (e) had sustained a blast or non-blast related injury (n = 571, 100% of total sample), (f) had been deployed 3 or fewer times (n = 445, 76.2% of total sample), (g) had completed the Neurobehavioral Symptom Inventory (NBSI)30 and PTSD Check List-Civilian Version (PCLC)31 within 12 months of injury (n = 495, 86.8% of total sample), and (h) had a AIS32 completed (n = 491, 86.0% of total sample).
Classification of uncomplicated mTBI was based on duration of loss of consciousness (LOC), duration of post-traumatic amnesia (PTA), and computed tomography or magnetic resonance imaging scans undertaken within the first few days and/or weeks post-injury. Uncomplicated mTBI was defined as PTA less than 24 hours, LOC less than 15 minutes, and the absence of intracranial abnormality on computed tomography or magnetic resonance imaging scan. It was our preference to apply diagnostic criteria for mTBI on the basis of the American Congress of Rehabilitation Medicine,33 World Health Organization,34 or Department of Defense35 guidelines. However, there were 2 limitations that prevented application of these criteria. First, Glasgow Coma Scale (GCS) scores were not generally available. Second, the available information regarding LOC was limited to categorical data that did not allow us to differentiate between those patients with LOC greater or lesser than 30 minutes (ie, LOC < 15 minutes and LOC 16–60 minutes). As such, a criterion of LOC less than 15 minutes was applied. Information regarding LOC and PTA was obtained from in theater medical records when available, direct examination of the patient in Germany and at Walter Reed, and clinical interview with the patient soon after their arrival at Walter Reed. Collateral information including eyewitness accounts or other supplementary documentation was also used when available.
The mean age of the sample was 26.6 years (SD = 6.6) and all were male (100%). All patients were evaluated within 12 months of injury (mean = 2.5 months, SD = 3.3, range = 0.1–11.9 months). The breakdown of time between injury and evaluation was as follows: 0–1 month = 59.8%, 1–2 months = 8.8%, 2–3 months = 5.1%, 3–5 months = 8.0%, 5–9 months = 9.5%, and greater than 6 months = 8.8%. The majority of the sample was injured during OIF (90.5%), with 9.5% injured during OEF. The mean number of deployments was 1.1 (SD = 0.3; 1 deployment = 68.6%, 2 deployments = 23.4%, 3 deployments = 8.0%). The majority of the sample was injured as a result of a blast exposure (85.4%), with 14.6% injured as a result of a non-blast exposure (eg, motor vehicle accident). The breakdown regarding LOC and PTA was as follows: LOC: 17.5% none, 54.7% less than 1 minute, 23.4% 1 to 15 minutes, 4.4% unknown; PTA: 73.8% less than 15 minutes, 12.0% 16 to 59 minutes, 14.1% 1 to 24 hours. Information relating to education level and ethnic background was not available, although a minimum of a High School diploma or GED is required for military enrollment.
MEASURES & PROCEDURE
The NBSI30 is a 22-item self-report measure of postconcussion symptoms (eg, headache, balance problems, nausea, fatigue, sensitivity to noise, irritability, sadness, nervousness, difficulty concentrating, difficulty remembering, visual problems). The NBSI requires the test taker to rate the presence/severity of each symptom on a 5-point scale as follows: 0 = none, 1 = mild, 2 = moderate, 3 = severe, and 4 = very severe. A total score is obtained by summing the ratings for the 22 items (range = 0–88). Three cluster scores were also generated on the basis of factor analytic work by Caplan and colleagues36: Somatic/sensory (Items: 1–3, 5–12; range: 0–44), Cognitive (Items: 13–16; range: 0–16), Affective (Items: 4, 17–22; range: 0–28).
The PTSD Check List-Civilian Version (PCLC)31 is a 17-item self-report measure of PTSD symptoms. The PCLC was patterned specifically after the DSM-IV37 criteria to address Category B, C, and D symptom criteria for PTSD. The PCLC requires the test taker to rate the presence/severity of each symptom on a 5-point scale as follows: 1 = not at all, 2 = a little bit, 3 = moderately, 4 = quite a bit, and 5 = extremely. A total score is obtained by summing the ratings for the 17 items (range = 17–85). Three cluster scores can be generated based on DSM-IV Category B (re-experiencing cluster; Items: 1–5, range: 5–25), Category C (avoidance cluster; Items: 6–12, range: 7–35), and Category D (hyperarousal cluster; Items: 13–17, range: 5–25) criteria.
The AIS32 is an anatomically-based, consensus-derived, global severity scoring system that classifies injuries to the body into six main regions (ie, head or neck, face, chest, abdominal or pelvic contents, extremities or pelvic girdle, and external). Injuries are rated on a 6-point ordinal scale that classifies injury severity as minor (1), moderate (2), serious (3), severe (4), critical (5), or maximal (6). The AIS scoring system has been in use since 1971 and has undergone periodic revisions. The most recent update, was in 2008, was the version used for this study. The AIS is traditionally interpreted using the ISS. The ISS is calculated by summing the squares of the highest AIS severity codes in each of the 3 most severely injured body region. The ISS ranges from 1 to 75. For the purposes of this study, a modified ISS score was calculated (ISSmod) designed to include only extracranial injuries. All AIS codes referring to intracranial injuries were not included in the calculation of ISSmod. The ISSmod, however, was calculated in the same manner as the ISS score described above. Participants were divided into 4 ISSmod groups on the basis of severity categories recommended by Stevenson and colleagues38: minor (ISS: 1–3), moderate (ISS: 4–8), serious (ISS: 9–15), severe (ISS: 16–24), and critical (ISS: 25–75). To reduce the number of comparison groups, the severe (n = 27) and critical (n = 5) categories were combined to form a single severe/critical group (n = 32). The 4 final ISSmod groups were as follows: minor (n = 17), moderate (n = 48), serious (n = 40), severe/critical (n = 32).
Demographics and injury characteristics
Descriptive statistics of demographic and injury characteristics by group are presented in Table 1. There were no significant main effects for age (P = .286) or days tested post injury (P = .065). Tukey's post hoc comparisons also revealed no significant differences among the 4 groups for these variables. Of particular note, however, medium to large effect sizes were found for some group comparisons for days tested post injury (ie, minor > serious [d = 0.48]; minor > severe/critical [d = 0.74]; moderate > severe/critical [d = 0.53]), indicating a trend for an inverse relation between days tested post injury and severity of bodily injuries. That is, as bodily injury severity increased, days tested post injury tended to decrease. Nonetheless, all pairwise comparisons between groups for days-tested post injury were not statistically significant.
Information regarding education or ethnicity of the sample was not available. For the remaining variables, formal statistical comparisons (ie, chi-square analyses) were not possible due to the large number of groups and small sample sizes. Neither chi-square statistics (due to small sample sizes in many cells) nor Fisher exact tests (requires 2 groups × 2 categories only) could be appropriately conducted. Nonetheless, an informal comparison of these variables revealed few appreciable differences between groups, with the exception of LOC. Almost 3 quarters (70.6%) of patients in the minor group had no reported LOC compared with fewer than 20% in the moderate (20.8%) group, and fewer than 3% in the serious (2.5%) and severe/critical (3.1%) groups.
NBSI Symptom Reporting
The relation between bodily injury severity (ISSmod) and postconcussion symptom reporting (NBSI total score) was examined using Pearson product-moment correlation analyses. There was a significant negative association between ISSmod scores and the NBSI total score (r = −0.358, P < .001) and the 3 NBSI cluster scores: somatic/sensory cluster (r = −0.300, P < .001), cognitive cluster (r = −0.373, P < .001), and affective cluster (r = −0.356, P < .001). As bodily injury severity increased, there was a decrease in self-reported postconcussion symptoms.
Descriptive statistics, group comparisons (non-parametric due to non-normal distributions), and effect sizes for the NBSI total score, the 3 cluster scores, and the individual item scores across the 4 groups are presented in Table 2. Given the large number of variables, pairwise comparisons were limited to total scores and cluster scores. Since the probability of Type 1 error increases when multiple statistical comparisons are made, Benjamini's and Hochberg's False Discovery Rate (FDR) was used to determine appropriate alpha levels for statistical significance.39 When determining the FDR, the observed individual P-values from a family of statistical tests as well as the number of tests are taken into account. For the data in Table 2, a statistical significance value of P < .033 was used to interpret main effects across the 4 groups (ie, total score, cluster scores, and individual symptoms), and P < .014 for all pairwise comparisons (ie, total scores and cluster scores).
There were significant main effects across the 4 groups for the NBSI total score (Kruskal Wallis H test: P = .001), all the 3 cluster scores (somatic/sensory, P = .006; cognitive, P < .001; and affective, P = .002), and 13 of the 22 individual item scores (range: P < .001 to P = .033). For the NBSI total score, pairwise comparisons (using Mann-Whitney U tests) revealed significant differences and medium-large to very large effect sizes for 3 of the 6 possible comparisons between groups (range: d = 0.69 to d = 1.0). Although not significant, medium effect sizes (d = 0.40 and d = 0.46) were also found for 2 additional comparisons. Overall, there was an inverse relation between severity of bodily injury and symptom reporting. Higher NBSI total scores were found for those patients with the least severe bodily injuries compared with those with more severe bodily injuries. A similar pattern of scores was also found for the 3 cluster scores. However, this pattern of scores was more apparent for the cognitive cluster (ie, 4 of 6 comparisons significant; 5 of 6 comparisons with medium-large to very large effect sizes: d = 0.59 to d = 1.21) than the somatic/sensory cluster (ie, 2 of 6 comparisons significant; 4 of 6 comparisons with medium to large effect sizes: d = 0.44 to d = 0.86) and the affective cluster (ie, 2 of 6 comparisons significant; 4 of 6 comparisons with medium to very large effect sizes: d = 0.49 to d = 0.96).
Comparison of the prevalence of endorsed symptoms was undertaken by considering all 22 individual symptoms simultaneously. The cumulative percentages of the number of participants who endorsed symptoms as “mild or greater”* in each group are presented in Table 3. Chi-square analyses were used to compare the cumulative percentages of patients who endorsed “x-or-more” symptoms (ie, ranging from x = 1 to x = 22) across all 4 groups (ie, pairwise comparisons; FDR P < .016). Overall, the greatest number of symptoms was endorsed by the minor group, followed by the moderate, serious, and severe/critical groups. For example, 82.4% of the minor group endorsed 11 or more symptoms at a mild level or greater, followed by 70.8% of the moderate group, 42.5% of the serious group, and 34.4% of the severe/critical group (P < .016 for 4 of the 6 possible comparisons: minor & moderate > serious & severe/critical). A similar pattern of scores was also found for many other score comparisons (particularly when patients endorsed 8 or more symptoms to 14 or more symptoms), but again there were some variations to this general finding (see Table 3).
Symptom criteria for PCD
The percentages of each group that met DSM-IV Category C symptom research criteria for Postconcussional Disorder (PCD) were calculated on the basis of symptom reporting as “mild or greater” and “moderate or greater.” A person was classified as meeting DSM-IV criteria for PCD if they (a) endorsed 3 or more of the Category C symptom criteria, and (b) endorsed subjective attention and memory complaints. For the purposes of these analyses, only 6 of the 8 Category C criteria were used because the NBSI items do not address 2 criteria (ie, Criterion 7 = Change in personality; Criterion 8 = Apathy or lack of spontaneity). The percentages of each group that met DSM-IV PCD criteria, based on symptom reporting as “mild or greater” and “moderate or greater,” were as follows: (a) mild or greater symptoms: minor (82.4%), moderate (79.2%), serious (50.0%), severe/critical (34.4%); (b) moderate or greater symptoms: minor (64.7%), moderate (50.0%), serious (30.0%), severe/critical (18.8%). Pairwise comparisons (using chi-square analyses) revealed significant differences in the proportion of patients that met PCD criteria across the 4 groups. Both the minor and moderate groups had significantly greater (all P < .05; FDR correction not applied) proportions of patients that met PCD criteria compared with both the serious and severe/critical groups when using symptom endorsed as “mild or greater” and “moderate or greater” (ie, minor & moderate > serious & severe/critical).
PCLC symptom reporting
The relation between bodily injury severity and PTSD symptom reporting (PCLC total score) was examined using Pearson product-moment correlation analyses. There was a significant negative association between ISSmod scores and the PCLC total score (r = −0.337, P < .001) and the 3 PCLC cluster scores: re-experiencing cluster (r = −0.230, P = .007), avoidance cluster (r = −0.310, P < .001), and hyperarousal cluster (r = −0.402, P < .001). As bodily injury severity increased, there was a decrease in self-reported symptoms on the PCLC.
Descriptive statistics and group comparisons (nonparametric due to nonnormal distributions) for the PCLC total scores, cluster scores, and individual item scores across the 4 groups are presented in Table 4. There were significant main effects (FDR corrected P-value = P < .029) across the 4 groups for the PCLC total score (Kruskal-Wallis H test: P = .002), 2 of the 3 cluster scores (avoidance, P = .009; hyperarousal, P < .001), and 9 of the 17 individual items (range: P < .001 to P = .012). For the PCLC total score, pairwise comparisons (using Mann-Whitney U tests) revealed significant differences (FDR corrected P-value = P < .012) and large effect sizes for 2 of the 6 possible comparisons between groups (range: d = 0.73 to d = 0.89). Although not significant, medium to medium-large effect sizes (d = 0.46 and d = 0.62) were also found for 2 additional comparisons. Overall, there was an inverse relation between severity of bodily injury and symptom reporting. Higher PCLC total scores were found for those patients with the least severe bodily injuries compared with those with more severe bodily injuries. A similar pattern of scores was also found for 2 of the 3 cluster scores. This pattern of scores was most predominant for the hyperarousal cluster (ie, 4 of 6 comparisons significant; large to very large effect sizes: d = 0.69 to d = 1.09) followed by the avoidance cluster (ie, 2 of 6 comparisons significant; 3 of 6 comparisons with medium to large effect sizes: d = 0.58 to d = 0.97).
Further comparison of the prevalence of endorsed symptoms was undertaken by considering all 17 individual symptoms simultaneously. The cumulative percentages of the number of participants who endorsed symptoms as “mild or greater”† in each group is presented in Table 5. Chi-square analyses were again used to compare the cumulative percentages of patients who endorsed “x-or-more” symptoms (ie, ranging from x = 1 to x = 17) across all 4 groups (ie, pairwise comparisons; FDR α = 0.014). Overall, the greatest number of symptoms was endorsed by the minor group, followed by the moderate, serious, and severe/critical groups. For example, 64.7% of the minor group endorsed 10 or more symptoms at a mild level or greater, followed by 58.3% of the moderate group, 37.5% of the serious group, and 25.0% of the severe/critical group. However, only 1 or 2 of the possible 6 pairwise comparisons were consistently significant (moderate > severe/critical or minor & moderate > severe/critical).
Symptom Criteria for PTSD
The percentages of each group that met DSM-IV symptom criteria for PTSD was calculated based on symptom reporting as “mild or greater” and “moderate or greater.” A person was classified as meeting DSM-IV criteria for PTSD if they endorsed (a) 1 or more Category B symptoms, (b) 3 or more Category C symptoms, and (c) 2 or more Category D symptoms. The percentages of each group that met DSM-IV PTSD criteria, based on symptom reporting as “mild or greater” and “moderate or greater,” were as follows: (a) mild or greater symptoms: minor (64.7%), moderate (50.0%), serious (37.5%), severe/critical (21.9%); (b) moderate or greater symptoms: minor (47.1%), moderate (33.3%), serious (27.5%), severe/critical (9.4%). Pairwise comparisons (using chi-square analyses) revealed significant differences in the proportion of patients that met PTSD criteria across the 4 groups. For symptoms reported as mild or greater, both the minor and moderate groups had significantly greater (all P < .05; FDR correction not applied) proportions of patients that met PTSD criteria compared with the severe/critical group (ie, minor & moderate > severe/critical). For symptoms reported as moderate or greater, the severe/critical groups had a significantly lower (all P < .05) proportion of patients that met PTSD criteria compared with the minor, moderate, and severe/critical groups (ie, minor, moderate, and serious > severe/critical).
Combat-related injuries resulting in medical evacuation can be psychologically traumatic, serious, and/or life threatening. When service members sustain mTBIs in the context of blast-related polytrauma, as was the case for 85% of the present sample, it can be challenging to monitor recovery from the mTBI and disentangle it from other physical and psychological injuries. During the post-acute recovery and rehabilitation phase, symptoms and problems associated with physical injuries, psychological distress, and mTBI can be overlapping and interwoven. Much additional research is needed in this area.
In this study, all service members sustained an mTBI in the context of polytrauma. Intuitively and based on the civilian literature, it would be expected that as physical injuries increased, risk for mental health problems and chronic pain would increase, and these comorbidities would increase postconcussion and traumatic stress symptom reporting. On the contrary, however, there was an inverse relation between the severity of bodily injuries and the reporting of traumatic stress and postconcussion symptoms. Those individuals who had sustained the greatest and most extensive bodily injuries reported fewer traumatic stress and postconcussion symptoms than those who experienced lesser bodily injuries. Similar to the study by Kennedy et al,29 this effect was seen both on total scores and on individual symptom clusters on the postconcussion and PTSD outcome measures. This effect was most pronounced on the most severely injured in this study, a group not included in the previous study. It could be expected that individuals with such severe injuries would have the most pain, the most visible effects of their injuries, and the most pessimism about their future. Instead, these individuals reported the fewest symptoms of all kinds, and had the lowest rates of individuals that met DSM criteria for postconcussive disorder and PTSD. These results are also consistent with the findings of a civilian sample39 in which injury severity showed no impact on traumatic stress in a multitrauma/spinal cord injury setting. These results are partially consistent with the large-scale civilian study by Bryant and colleagues (2010) in that polytrauma cases with “critical” injury severity scores had the lowest rates of new-onset mental health problems at 3 and 12 months post injury (although civilians classified as having moderate or severe bodily injuries had greater rates of mental health problems).
Bryant and colleagues (2010) reported that 28.7% of civilians with polytrauma and mTBI had a diagnosed psychiatric disorder at 3 months post injury. A major depressive episode was documented in 17.9%, agoraphobia in 14.8%, PTSD in 12.7%, and generalized anxiety disorder in 9.8% (some of the patients had multiple diagnoses). In the present study, a much greater percentage of military polytrauma cases met our screening criteria for PTSD than in the civilian study by Bryant and colleagues. The percentages of each group that met DSM-IV PTSD criteria, based on symptom reporting as “mild or greater” and “moderate or greater,” were as follows: (a) mild or greater symptoms: minor (64.7%), moderate (50.0%), serious (37.5%), severe/critical (21.9%), (b) moderate or greater symptoms: minor (47.1%), moderate (33.3%), serious (27.5%), severe/critical (9.4%). The civilian-military differences might, in part, be due to methodological differences, in that the Bryant study used semi-structured interviewing and we used questionnaires. It might also be due, in part, to the more traumatic circumstances associated with combat-related polytrauma.
There are several possible explanations for the inverse relation between the severity of bodily injuries and postconcussion and traumatic stress symptom reporting. First, it may be a matter of relative perspective. Those with the most severe physical injuries have typically endured multiple surgeries and medical procedures, and in some cases might not have survived except for the expert, timely medical care they received. In that context, postconcussive and PTSD symptoms might be viewed as minor “inconveniences” and pale in comparison to the potential loss of life that they faced. That is, this more seriously injured group may be underreporting actual levels of distress.
Second, severe corporeal injury provides a visible daily reminder of one's injuries. This visible injury shows visible healing over time, allowing one to mark progress. Even in those “unhealable” injuries such as limb loss, a patient can advance to the use of a prosthetic and walk or grasp objects again. These tangible markers of progress provide reassurance that rehabilitation and recovery are progressing. On the contrary, small incremental progress in recovery from attentional difficulties, memory concerns, headaches, or other concerns may not be as striking, inducing pessimism or the belief that symptoms are persisting without relief. This possibility raises the question of whether symptoms may actually increase over time as the physical issues heal.
Third, social supports or related factors may be protective for some with visible injuries. For example, at WRAMC, amputees have a cohesive peer support network40,41 that offers high levels of satisfaction and happiness about outcomes. Although the overall rate of PTSD is significant in military amputees (18%), it is lower than in the larger group of injured service members,42 suggesting that some factors related to cohesion or support might provide a buffer against symptoms. For those with less visible injuries, it may be harder to obviously identify peers for support, or there may issues of stigma that prevent the formation of these protective networks. Again, this raises the possibility that service members might be at risk for worsening of symptoms as they heal and move away from that level of ongoing support.
A fourth possibility is related to the acute period following injury. Recent work43 has shown that acute administration of morphine may disrupt fear conditioning, resulting in lower rates of PTSD in those administered the drug. Some researchers have reported that injuries to the brain that result in loss of consciousness and posttraumatic amnesia are protective against PTSD because of the limited encoding of the traumatic experience.44–46 Low rates of PTSD have been reported in individuals who have sustained TBI with loss of consciousness in both military47 and civilian populations.48,49 Although the duration of LOC related to the TBI was generally equivalent in these groups, it is possible that many were later sedated for transport due to their injuries. Consolidation of traumatic memories may have been prevented, thereby lowering later posttraumatic stress and other symptoms that have been already linked to stress expression.
A final possibility may be related to time since injury. As the more severely injured tended to have been evaluated sooner, it may be that the symptoms are not as obvious to the subjects at the point they were queried. That is, it is possible that these more severely injured service members will develop more symptoms as time since injury increases. Four patterns of trajectory for psychological functioning following traumatic physical injuries have been identified.50 Some individuals show a delayed expression of PTSD and depression. The 3-month period is the time at which individuals appear to reach a crucial point toward a trajectory of delayed symptoms or recovery. Previous work at WRAMC7 in a non-TBI population showed that early severity of physical problems was strongly associated with PTSD and depression at 7 months post injury. The majority of service members with PTSD or depression at 7 months did not meet criteria for either condition at 1 month following injury.
This study has several methodological limitations. First, the timing of the collection of outcome measures in this military Medical Center was influenced by clinical and administrative factors. This resulted in a number of subjects from the larger sample not meeting inclusion criteria. Second, the accurate identification of mTBI in combat-injured polytrauma cases is complex—and it is possible that we have included a small number of patients who did not sustain an obvious mTBI and a few who might have sustained a more serious injury. Third, the outcome measures used, as in most studies, were self-report questionnaires. We did not utilize semi-structured interviewing for diagnosing PTSD or for postconcussional disorder. Fourth, we were unable to include a group of patients with severe bodily injuries that were assessed further from the time of injury. The inclusion of this group would have been useful to more completely determine the impact of a longer recovery period on symptom reporting. Fifth, those individuals farther out from the point of injury may have included individuals who were referred to Walter Reed after poor recovery in other settings, as opposed to individuals admitted here soon after their injuries. Finally, similar to most other studies, no measures of effort or validity were included in this study. Much remains to be known about resilience in the face of severe physical injury. It may be that the majority of those with severe physical injury adjust well to their injuries. It is unknown whether a subset with long term physical disabilities related to their injuries may have a different course. These results argue for careful assessment and monitoring of the psychological state of all those that are combat injured, not just the most severely affected. These findings also speak to the need for longitudinal studies to determine if the “protective” effect of severe extracranial injury is temporary or long-term and what factors mitigate an individual's response to that trauma.
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* Similar findings were also found when comparing NBSI symptoms endorsed as “moderate or greater”. These data are not presented here but can be obtained from RTL on request.
† Similar findings were also found when comparing PCLC symptoms endorsed as “moderate or greater”. These data are not presented here but can be obtained from RTL on request.