Risk Factors for Postconcussion Symptom Reporting after Traumatic Brain Injury in U.S. Military Service Members

Abstract

The purpose of this study was to identify factors that are predictive of, or associated with, postconcussion symptom reporting after traumatic brain injury (TBI) in the U.S. military. Participants were 125 U.S. military service members (age: M=29.6 years, standard deviation [SD]=8.9, range=18–56 years) who sustained a TBI, divided into two groups based on symptom criteria for postconcussional disorder (PCD): PCD-Present (n=65) and PCD-Absent (n=60). Participants completed a neuropsychological evaluation at Walter Reed Army Medical Center (M=9.4 months after injury, SD=9.9; range: 1.1 to 44.8). Factors examined included demographic characteristics, injury-related variables, psychological testing, and effort testing. There were no significant group differences for age, sex, education, race, estimated premorbid intelligence, number of deployments, combat versus non-combat related injury, or mechanism of injury (p>0.098 for all). There were significant main effects for severity of body injury, duration of loss of consciousness, duration of post-traumatic amnesia, intracranial abnormality, time tested post-injury, possible symptom exaggeration, poor effort, depression, and traumatic stress (p<0.044 for all). PCD symptom reporting was most strongly associated with possible symptom exaggeration, poor effort, depression, and traumatic stress. PCD rarely occurred in the absence of depression, traumatic stress, possible symptom exaggeration, or poor effort (n=7, 5.6%). Many factors unrelated to brain injury were influential in self-reported postconcussion symptoms in this sample. Clinicians cannot assume uncritically that endorsement of items on a postconcussion symptom checklist is indicative of residual effects from a brain injury.

Introduction

S ymptoms after mild traumatic brain injury (MTBI) largely resolve in most persons within the first week to 6 months after injury. Symptom resolution tends to be faster in young, healthy, athletes¹ and slower in civilians injured in accidents or daily life^2
–4 or military service members injured during combat or non-combat related incidents.⁵ Some persons continue to report symptoms many months post-injury.^6
–8 Symptoms have been reported in persons who are 1 or more years post-injury,^9
–11 and up to 5 years post-injury in a recent military study.⁵ Recent research, however, has found that a substantial minority of people who report clinically significant postconcussion symptoms (i.e., consistent with Diagnostic and Statistical Manual of Mental Disorders [DSM]-IV/International Classificastion of Diseases [ICD]-10 criteria for postconcussional disorder/syndrome) many months or years post-injury do not always report consistent and persistent symptoms from baseline to follow-up. Rather, a substantial minority of persons report newly developed or substantially worsened symptoms 3 to 12 months after MTBI in a civilian population,^12
–14 and many months or years after MTBI in a military population.^5,15 The development of new or substantially worsened postconcussion-like symptoms 3–12 months after injury has also been reported in civilian patients who have sustained orthopedic injuries without brain injury.^13
–15

It is important to appreciate that many non-TBI factors can cause, maintain, or mimic self-reported PCD symptoms (e.g., comorbidities, social-psychological factors, or legal factors).^16
–18 PCD symptoms are not unique to MTBI alone, and these symptoms often overlap with a number of pre-existing and/or co-occurring conditions, or are present because of other factors such as poor effort or exaggeration. In a civilian setting, researchers have repeatedly demonstrated that healthy adults report postconcussion-like symptoms,^19
–21 as do persons with psychiatric disorders, personal injury claims, chronic pain, posttraumatic stress disorder (PTSD), and soft tissue injuries.^22

–26 Complicating matters further, the perception and reporting of symptoms long after MTBI can be influenced by premorbid personality characteristics (e.g., narcissistic, avoidant, dependent, and borderline personality traits),^27
–29 depression,^30,31 and a diverse range of social-psychological factors (e.g., expectations, misattribution, and an idealized view of pre-injury functioning.^32,33

–36 In addition, the influence of poor effort on self-reported symptoms has been illustrated in both civilian and military studies. Persons who fail effort tests report significantly more self-reported symptoms on postconcussion checklists^37

–40 and personality inventories^41
–43 compared with those who pass effort testing. Similarly, possible symptom exaggeration on self-report measures is common in civilian and military samples after mild TBI or in those evaluated or treated for PTSD.^{39,44

–48}

In a military setting, MTBI is often associated with exposure to emotionally traumatic events and co-occurring physical injuries. PTSD, a subsyndromal traumatic stress condition, or chronic pain might develop in service members. PCD symptoms have been endorsed by military personnel after episodes of in-theater distressing experiences, even with no causal link to an event that might result in a brain injury (i.e., aiding the wounded⁴⁹). Even in the absence of brain injury, polytrauma patients endorse high rates of psychological and neurobehavioral symptoms, including memory problems, significant mood symptoms, and amotivation.⁵⁰ Service members from Operation Enduring Freedom and Operation Iraqi Freedom (OEF/OIF), who have sustained an MTBI and report PCD symptoms, often have mental health comorbidities such as PTSD, depression, anxiety, somatoform disorders, and substance abuse, with PTSD and depression the most common.^51

–56 Researchers have found that PTSD and depression largely explain the relationship between a history of MTBI and PCD symptom reporting, in addition to other general health problems.^{14,51,52,57,58} Mental health problems also tend to intensify with time.^59

–62 In a sample of service members returning from Iraq, less mental health distress was reported immediately on return from deployment compared with 4–10 months later.⁶¹

The ability to identify those at risk for reporting long-term symptoms is advantageous for providing high quality clinical care. Early detection of patients in the acute recovery phase who are at risk of poor outcome can potentially result in early treatment and the opportunity to minimize the possibility of poor long-term outcome. Early intervention programs for civilians who have sustained MTBIs are helpful for some^63
–65 but certainly not all persons,⁶⁶ and early intervention for traumatic stress reduces the likelihood of PTSD developing.^67
–69 To date, although many researchers have examined a single or a small number of factors that can influence or predict PCD symptom reporting (e.g., depression, PTSD, diffusion tensor imaging, and “good old days” bias), few researchers have examined a large range of variables concurrently to identify those factors that provide the most unique contribution to PCD symptom reporting. Of those studies that have examined more than 4–5 factors, all studies have been undertaken in a civilian population, and the vast majority of studies have concluded that factors unrelated to brain injury (e.g., depression, PTSD, anxiety, cognitive deficits, fatigue, premorbid anxiety or affective disorders, pain, poor balance, health status, symptom exaggeration, and poor effort) were the most significant predictors of postconcussion symptom reporting.^26,70

–73

The purpose of this study is to identify factors that are predictive of, or associated with, PCD symptom reporting after TBI in U.S. military service members. A total of 19 factors, grouped into three broad categories, were examined: (1) demographic characteristics (age, education, sex, race, estimated premorbid intellectual ability), (2) injury-related variables (time tested post-injury, number of deployments, combat versus non-combat related injury, body injury severity, duration of post-traumatic amnesia, duration of loss of consciousness, mechanism of injury, acute intracranial abnormality), and (3) psychological testing and effort testing (depression, traumatic stress, symptom exaggeration, and effort test performance). The hypotheses were twofold. First, demographic characteristics would have a weak association with, and would not be predictive of, PCD symptom reporting. Second, psychological and effort testing factors would be highly associated with, and predictive of, PCD symptom reporting.

Methods

Participants

Participants were 125 U.S. military service members (age: M=29.6 years, standard deviation [SD]=8.9, range=18–56 years) who sustained a TBI and were evaluated at the Walter Reed Army Medical Center (WRAMC), Washington, DC, after injuries sustained (1) while deployed during OIF (n=93, 74.4%) or OEF (n=8, 6.4%), or (2) as a result of other non-combat related operations/incidents (n=24, 19.2%). Severity of TBI (described in more detail below) was as follows: (1) 57 uncomplicated MTBI (45.6%), (2) 14 complicated MTBI (11.2%), (3) 23 moderate TBI (18.4%), and (4) 31 severe TBI (24.8%). The sample consisted of two groups: (1) 65 patients who met modified DSM-IV criteria for postconcussional disorder (PCD-Present), and (2) 60 patients who did not meet modified DSM-IV criteria for postconcussional disorder (PCD-Absent; see Measures and Procedures for classification criteria).

Patients were selected from a larger sample of 251 U.S. military service members who had been referred to the TBI clinic at WRAMC for neuropsychological consultation more than 1 month post-injury, but not greater than 4 years post-injury. All patients were treated at WRAMC between January 2002 and March 2008 after a suspected or confirmed TBI and had agreed to the use of their clinical data for research purposes. Patients were included in the selected sample if they: (1) had sustained a closed TBI (n=232, 92.4% of sample), (2) had completed the Personality Assessment Inventory (PAI, n=199, 79.3% of sample), (3) had been administered the Word Memory Test (WMT, n=224, 89.2% of sample; 33.5% failed), and (4) had completed the Neurobehavioral Symptom Inventory (NSI) and PTSD Checklist-Civilian (PCL-C, n=230, 91.6% of sample). The mean time tested post-injury was 9.4 months (SD=9.9; range: 1.1–44.8 mos). The breakdown of time post-injury was as follows: 1–3 months (22.4%), 3–6 months (28.8%), 6–12 months (27.2%), 12–24 months (11.2%), and 24–44 months (10.4%).

Classification of brain injury severity was based primarily on duration of loss of consciousness (LOC) and post-traumatic amnesia (PTA). Glasgow Coma Scale (GCS) scores are often not available shortly after combat-related injuries and were not available for use. TBI injury severity was defined as follows: (1) uncomplicated MTBI: PTA <24 h, LOC <15 min, and intracranial abnormality absent; (2) complicated MTBI: PTA <24 h, LOC <15 min, and intracranial abnormality present; (3) moderate TBI: PTA=24 h to 7 days and LOC <24 h; and (4) severe TBI: PTA >7 days. With regard to the classification of MTBI, it was our preference to use a LOC criterion of <30 min, consistent with commonly used diagnostic criteria.^74
–76 The available information regarding LOC, however, was limited to categorical data that did not allow us to differentiate between duration of LOC greater than, or less than, 30 min (i.e., available data=LOC <15 min and LOC 16–60 min).

The protocols under which these data were collected were approved by the Institutional Review Board of WRAMC. This study was completed in accordance with the guidelines of the Declaration of Helsinki.

Measures and procedure

Measures were selected from a larger neuropsychological test battery (approximately 6 h) designed to provide comprehensive documentation of cognitive and psychological functioning. The measures selected were as follows: (1) NSI,⁷⁷, (2) PCL-C,⁷⁸ (3) PAI,⁷⁹ (4) Wechsler Test of Adult Reading [WTAR⁸⁰], demographics-predicted Full Scale Intelligence Quotient (FSIQ), and (5) WMT.⁸¹ For the WTAR, the reading score was not available for all patients, so the demographics formula was used to predict FSIQ. Patients were classified as having passed/failed the WMT based on a test performance that fell below the cutoff scores recommended in the manual.⁸¹ In addition to these measures, information regarding injury characteristics and demographic information was obtained from medical records (i.e., age, sex, race, education, number of deployments, geographical location of injury, mechanism of injury, body injury severity, LOC, PTA, and neuroimaging).

Participants were classified as meeting DSM-IV modified criteria for PCD based on symptom reporting on the NSI. The NSI is a 22-item measure designed to evaluate self-reported post-concussion symptoms (e.g., headache, balance problems, nausea, fatigue, sensitivity to noise, irritability, sadness, nervousness, difficulty concentrating, difficulty remembering, visual problems). The NSI 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 person was classified as meeting DSM-IV criteria for PCD if they (1) endorsed three or more of the Category C symptoms at a moderate level of higher, and (2) endorsed subjective complaints of attention or memory problems at a moderate level or higher. Category D criteria require objective evidence of cognitive impairment in attention or memory. For the purposes of this study, subjective reports of these cognitive complaints were used as a proxy. Note that only the first six of the eight Category C symptom criteria for PCD can be addressed by these items.

The PCL-C is a 17-item measure designed to evaluate self-reported traumatic stress symptoms. The PCL-C was patterned specifically after the DSM-IV criteria to address Category B, C, and D symptom criteria for PTSD. The PCL-C 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). Participant's responses on the PCL-C can also be classified based on DSM-IV criteria for PTSD determined using symptoms reported as “moderate or greater” (i.e., 3, 4, or 5). Responses on the PCL-C were classified as meeting “Possible” DSM-IV criteria for PTSD if the respondent had a PCL-C total score of 36 or greater and endorsed (1) one or more of the Criterion B symptoms (questions 1–5), (2) three or more of the Criterion C symptoms (questions 6–12), and (3) two or more of the Criterion D symptoms (questions 13–17). Responses on the PCL-C were classified as meeting “Probable” DSM-IV criteria for PTSD if the respondent had a PCL-C total score of 50 or greater and endorsed the symptom criteria above.

The PAI is a 344-item measure designed to assess psychological symptomatology. The PAI generates four validity scales, 18 clinical scales, and 31 clinical subscales. For this study, only four scales/subscales measuring depression and symptom exaggeration were included: Suicidal Ideation, Depression-Cognitive, Depression-Affective, and Negative Impression Management (NIM). These scales/subscales were chosen because their item content is considered to be hallmark symptoms of depression that were least likely to overlap with PCD. The item content of the Depression-Cognitive and Depression-Affective scales is heavily weighted toward depressive negativism (negative view of self, life, and future), sadness, loss of interest in activities, and anhedonia. For one set of analyses, screening positive for depression was defined as having T-scores of 60 or greater on both the Cognitive and Affective subscales.

The Abbreviated Injury Scale (AIS)⁸² is an anatomically based, consensus-derived, global severity scoring system that classifies injuries to the body categorized into six main regions (i.e., head or neck, face, chest, abdominal or pelvic contents, extremities or pelvic girdle, and external). Injuries are rated on a six-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, which was the version used for this study. The AIS is traditionally interpreted using the Injury Severity Score (ISS). The ISS is calculated by summing the squares of the highest AIS severity codes in each of the three most severely injured body regions. The ISS ranges from 1 to 75. For the purposes of this study, a modified ISS score was calculated (ISS_mod) to include only extracranial injuries. All AIS codes that included intracranial injuries were not included in the calculation of ISS_mod. The ISS_mod, however, was calculated in the same manner as the ISS score described above. Classification categories, as recommended by Stevenson and colleagues,⁸³ were as follows: Minor (ISS_mod 1–3), Moderate (ISS_mod 4–8), Serious (ISS_mod 9–15), Severe ISS_mod 16–24), and Critical (ISS_mod 25–75).

Results

Demographic and injury variables

Descriptive statistics and group comparisons of demographic characteristics and injury-related variables, by PCD group, are presented in Tables 1 to 2. For the demographic characteristics (Table 1), there were no significant differences between groups for age, sex, education, race, or estimated premorbid intellectual ability. For the clinical and injury-related variables (Table 2), there were no significant differences between groups for the number of deployments at the time of injury, combat versus non-combat related injury, or mechanism of injury. There were, however, significant differences for severity of body injury (p=0.004 and p=0.032), duration of LOC (p=0.007 and p=0.006), duration of PTA (p=0.009 and p=0.044), time tested post-injury (p=0.009 and p=0.010), and the presence of intracranial abnormality in the acute injury phase (p<0.001). The PCD-Present group sustained less severe body injuries and less severe brain injuries (as indicated by a shorter duration of PTA and LOC). The PCD-Present group was more likely to have a body injury classified as minor or moderate (odds ratio [OR]=2.81, relative risk [RR]=1.55), a duration of LOC less than 15 min (OR=3.35, RR=1.97), and a duration of PTA less than 24 h (OR=2.10, RR=1.44). In addition, the PCD-Present group was more likely to have no intracranial abnormality (OR=4.54, RR=2.15) and more likely to have been tested 12 or more months post-injury compared with the first 3 months post-injury (OR=6.00, RR=2.66).

Table 1.

Descriptive Statistics and Group Comparison of Demographic Characteristics by Group

	PCD present		PCD absent
	M	SD	M	SD	p	d	Effect size
Age (in years)	29.8	8.8	29.3	9.2	0.764	0.05	Very small
WTAR: Demo estimated FSIQ	103.6	6.1	104.6	5.9	0.362	0.16	Small

	N	%	N	%	X²	OR (95% CI)	RR (95% CI)
Sex
Male	61	53.0	54	47.0	0.428	1.69 (0.40–7.62)	1.33 (0.70–3.96)
Female	4	40.0	6	60.0
Education
Greater than 12 years	39	53.4	34	46.6	0.706	1.15 (0.53–2.49)	1.07 (0.74–1.58)
GED/12 years	26	50.0	26	50.0
Race
Other	15	65.2	8	34.8	0.160	1.95 (0.70–5.56)	1.33 (0.83–1.82)
Caucasian	50	49.0	52	51.0

N=125 (65 PCD-Present, 60 PCD-Absent).

PCD=postconcussional disorder; SD=standard deviation; WTAR=Wechsler Test of Adult Reading; FSIQ=Full Scale Intelligence Quotient; OR=odds ratio; RR=relative Risk; CI=confidence interval; GED=general education diploma.

Table 2.

Descriptive Statistics and Group Comparison of Injury-Related Variables by Group

	PCD-present		PCD-absent
	M	SD	M	SD	p	d	Effect size
AIS-ISS_mod: 5 categories)^a	2.4	1.0	3.2	1.3	0.004	0.71	Med-large
LOC: 7 categories^b	2.5	1.5	3.3	1.9	0.007	0.50	Medium
PTA: 8 categories^b	4.1	2.0	5.1	2.1	0.009	0.48	Medium
Time tested post-injury (mos)	10.8	10.3	7.9	9.3	0.009	0.30	Small-med
Deployment number^a	1.4	0.8	1.4	0.7	0.948	0.01	Very small

	N	%	N	%	X²	OR (95% CI)	RR (95% CI)
Where wounded
OIF/OEF	54	53.5	47	46.5	0.501	1.36 (0.51–3.63)	1.17 (0.75–2.11)
Other non-combat related	11	45.8	13	54.2
Mechanism of injury
Blast	49	57.0	37	43.0	0.098	1.90 (0.83–4.41)	1.39 (0.91–2.26)
Non-blast	16	41.0	23	59.0
Body injury (AIS-ISS_mod)^a
Minor/moderate	25	69.4	11	43.0	0.032	2.81 (0.98–8.20)	1.55 (0.99–2.38)
Serious/severe/critical	17	44.7	21	55.3
Loss of consciousness
<1–15 minutes	56	58.9	39	41.1	0.006	3.35 (1.29–8.91)	1.97 (1.13–3.90)
15 min+	9	30.0	21	70.0
Post-traumatic amnesia
<1 min to 24 h	44	59.5	30	40.5	0.044	2.10 (0.95–4.63)	1.44 (0.98–2.20)
24 h+	21	41.2	30	58.8
Day-of-injury intracranial abnormality
Normal	48	67.6	23	32.4	<0.001	4.54 (1.99–10.48)	2.15 (1.40–3.39)
Abnormal	17	31.5	37	68.5
Months tested post-injury
12 months or more	18	66.7	9	33.3	0.010	6.00^b (1.61–23.35)	2.66^b (1.30–5.79)
6–12 months	19	55.9	15	44.1		3.80^b (1.13–13.20)	2.24^b (1.07–5.15)
3–6 months	21	58.3	15	41.7		4.20^b (1.26–14.43)	2.33^b (1.14–5.32)
1–3 months	7	25.0	21	75.0		n/a	n/a

N=125 (65 PCD-Present, 60-PCD Absent). Exceptions: Deployment number, n=74 (47 PCD-Present, 27 PCD-Absent), and AIS-ISS_mod, n=74 (42 PCD-Present, 32 PCD-Absent).

PCD=postconcussional disorder; SD=standard deviation; AIS=Abbreviated Injury Scale; ISS=Injury Severity Score; LOC=loss of consciousness; PTA=post-traumatic amnesia; OR=odds ratio; RR=relative risk; CI=confidence interval; OIF=Operation Iraqi Freedom; OEF=Operation Enduring Freedom.

Sample size was too small to consider inclusion in subsequent regression analyses.

Versus 1–3 month period.

Psychological and effort testing measures

Descriptive statistics and group comparisons for the psychological and effort tests, by PCD group, are presented in Table 3. There were significant differences between groups on all measures (all p<0.001), except WMT Consistency. The PCD-Present group had higher scores on the PAI NIM (d=1.27) and Suicide scales (d=0.77), the PAI Depression-Cognitive (d=1.30) and Depression-Affective subscales (d=1.70), and the PCL-C total score (d=1.70). The PCD-Present group had lower scores on the WMT Immediate Recognition (d=0.82) and Delayed Recognition (d=0.85) scores.

Table 3.

Descriptive Statistics and Group Comparison of the Psychological and Validity Measures by Group

	PCD-present		PCD-absent
	M	SD	M	SD	p	d	Effect size
PAI: Suicide scale	52.3	12.1	46.0	3.7	<0.001	0.77	Large
PAI: DEP-Cognitive	63.4	13.6	48.8	8.6	<0.001	1.30	Very large
PAI: DEP-Affective	68.3	13.9	49.4	8.2	<0.001	1.70	Very large
PAI: Negative Impression Management	61.8	12.0	49.2	7.7	<0.001	1.27	Very large
PCL-C total score	51.3	17.1	28.3	9.7	<0.001	1.70	Very large
WMT Immediate Recognition	82.4	18.0	93.8	9.5	<0.001	0.82	Large
WMT Delayed Recognition	80.1	19.0	93.4	11.9	<0.001	0.85	Large
WMT Consistency	75.1	25.5	74.1	37.0	0.849	0.03	Very small

N=125 (65 PCD Present, 60 PCD Absent).

PCD=postconcussional disorder; SD=standard deviation; PAI=Personality Assessment Inventory; DEP=depression; PCLC=PTSD Checklist-Civilian Version; WMT=Word Memory Test.

Prediction of NSI total scores

To determine which factors provide the most unique contribution to the prediction of post-concussion symptom reporting, a series of linear regression analyses were undertaken to determine if NSI total scores could be predicted by 10 selected variables examined in Tables 1 to 3. Variables were only included in the analyses if they were significantly different between groups. Variables selected were as follows: time tested post-injury, duration of LOC, duration of PTA, intracranial abnormality, PAI NIM scale, poor effort on the WMT, PAI Suicide scale, PAI Depression-Cognitive subscale, PAI Depression-Affective subscale, and the PCL-C total score. Linear regression analyses results are presented in Table 4.

Table 4.

Standard Regression Analyses of Selected Variables To Predict NSI Total Score

	Parameter estimates			Model summary
Measures	β	t	p_t	p_F	R²
Model 1				<0.001	65.8
Constant		−2.925	0.004
PCL-C total score	0.485	5.932	<0.001
PAI: DEP-Affective	0.268	3.256	0.001
WMT: poor effort (present/absent)	0.167	2.618	0.010
Model 2				<0.001	59.3
Constant		−0.995	0.322
PCL-C total score	0.770	13.389	<0.001
Model 3				<0.001	51.4
Constant		−4.961	<0.001
PAI: DEP-Affective	0.717	11.409	<0.001
Model 4				<0.001	30.7
Constant		12.565	<0.001
WMT: poor effort (present/absent)	0.554	7.389	<0.001

N=125 (65 PCD-Present, 60 PCD-Absent).

PCL-C=PTSD Checklist-Civilian Version; PAI=Personality Assessment Inventory; DEP=Depression; WMT=Word Memory Test.

Using step-wise regression analyses, all 10 factors were first entered simultaneously as the dependent variables, and the NSI total score as the independent variable. The majority of variables were not significant predictors of the NSI total score and were not included in the final model. Only three variables were significant predictors of the NSI total score: the PCL-C total score (p<.001), PAI Depression-Affective subscale (p=0.001), and poor effort on the WMT (p=0.010). Together, these three variables accounted for 65.8% of the variance (p<0.001) in the prediction of the NSI total score. Three additional analyses were undertaken using each of these three factors as dependent variables separately, and the NSI total score as the independent variable (Table 4). All three factors were significant predictors of NSI total scores when entered separately (all p<0.001). The largest percentage variance was accounted for by the PCL-C total score (59.3%), followed by the PAI Depression-Affective subscale (51.4%) and the WMT (30.7%).

Depression, traumatic stress, exaggeration, and effort

Clinically derived cutoff scores on measures of depression, traumatic stress, symptom exaggeration, and poor effort were used to examine further the relation between these variables and the presence of PCD. Various cutoff scores and factors were evaluated singularly, and in combination, grouped into two categories as follows: (1) effort and validity testing factors (i.e., PAI NIM scale [≥65T, ≥70T] and WMT [pass/fail]) and (2) psychological factors (i.e., “Possible” and “Probable” PTSD [present/absent], PAI Suicide scale, PAI Depression-Cognition subscale, and PAI Depression-Affective subscale [all >60T]). Variables were selected based on their ability to discriminate between the two PCD groups from the previous analyses based on (1) high OR or RR values (i.e., WMT) or large to very large effect sizes between groups (i.e., PAI Suicide scale, PAI Depression-Cognitive subscale, PAI Depression-Affective subscale, and PAI NIM scale), or (2) the variable being a significant predictor of NSI total scores (i.e., WMT, PAI Depression-Affective subscale, PCL-C total score). OR and RR values for these variables are presented in Table 5.

Table 5.

Depression, Traumatic Stress, Possible Exaggeration, and Poor Effort Subgroup Comparisons

	PCD–present		PCD–absent
Risk factor	N	%	N	%	X ²	OR (95% CI)	RR (95% CI)
Effort
WMT Fail	36	81.8	8	18.2	<0.001	8.07 (3.08–21.83)	2.29 (1.63–2.93)
WMT Pass	29	35.8	52	64.2
Symptom validity
NIM ≥70	21	91.3	2	8.7	<0.001	13.84 (2.89–90.40)	2.12 (1.53–2.37)
NIM <70	44	43.1	58	56.9
NIM ≥65	25	92.6	2	7.4	<0.001	18.13 (3.83–117.57)	2.27 (1.68–2.52)
NIM <65	40	40.8	58	59.2
Effort and validity
WMT Fail and NIM ≥70	11	100	0	0	<0.001	n/a^a	2.11 (1.38–2.11)
Not selected	54	47.4	60	52.6
WMT Fail and NIM ≥65	19	100	0	0	<0.001	n/a^a	2.30 (1.72–2.30)
Not selected	46	43.4	60	56.6
Not selected	42	80.8	10	19.2	<0.001	9.13 (3.64–23.48)	2.56 (1.79–3.47)
WMT Pass and NIM <65	23	31.5	50	68.5
Not selected	42	80.8	10	19.2	<0.001	9.13 (3.64–23.48)	2.56 (1.79–3.47)
WMT Pass and NIM <70	23	31.5	50	68.5
PTSD
“Possible” PTSD	41	89.1	5	10.9	<0.001	18.79 (6.09–62.10)	2.93 (2.12–3.61)
PTSD-Absent	24	30.4	55	69.6
“Probable” PTSD	37	90.2	4	9.8	<0.001	18.50 (5.53–68.32)	2.71 (1.99–3.21)
PTSD-Absent	28	33.3	56	66.7
Depression
DEP-Cog ≥60	32	82.1	7	19.7	<0.001	7.34 (2.70–20.75)	2.14 (1.54–2.63)
Not selected	33	38.4	53	61.6
DEP-Aff ≥60	48	87.3	7	12.7	<0.001	21.38 (7.50–63.66)	3.59 (2.45–4.89)
Not selected	17	23.4	53	75.7
SUI ≥60	12	100	0	0	<0.001	n/a^a	2.13 (1.43–2.13)
Not selected	53	46.9	60	53.1
DEP-Cog ≥60 and DEP-Aff ≥60 and SUI ≥60	11	100	0	0	0.001	n/a^a	2.11 (1.38–2.11)
Not selected	54	57.4	60	52.6
DEP-Cog ≥60 or DEP-Aff ≥60 or SUI ≥60	49	81.7	11	18.3	<0.001	13.64 (5.33–35.88)	3.32 (2.19–4.92)
Not selected	16	24.6	49	75.4
Possible PTSD and DEP¹
PTSD-Present and DEP-Cog ≥60 and DEP-Aff ≥60	28	93.3	2	6.7	<0.001	21.95 (4.65–141.96)	2.40 (1.79–2.66)
Not selected	37	38.9	58	61.1
PTSD-Present or DEP-Cog ≥60 or DEP-Aff ≥60	53	80.3	13	19.7	<0.001	15.97 (6.13–42.78)	3.95 (2.43–6.65)
Not selected	12	20.3	47	79.7
PTSD-Present and (DEP-Cog ≥60 or DEP-Aff ≥60)	37	92.5	3	7.5	<0.001	25.11 (6.59–112.34)	2.81 (2.09–3.23)
Not selected	28	32.9	57	67.1
Probable PTSD and DEP¹
PTSD-Present and DEP-Cog ≥60 and DEP-Aff ≥60	26	96.3	1	3.7	<0.001	39.33 (5.31–810.54)	2.42 (1.83–2.57)
Not selected	39	39.8	59	60.2
PTSD-Present or DEP-Cog ≥60 or DEP-Aff ≥60	53	80.3	13	19.7	<0.001	15.97 (6.13–42.78)	3.95 (2.43–6.65)
Not selected	12	20.3	47	79.7
PTSD-Present and (DEP-Cog ≥60 or DEP-Aff ≥60)	33	94.3	2	5.7	<0.001	29.91 (6.35–193.24)	2.65 (2.00–2.94)
Not selected	32	35.6	58	64.4

N=125 (65 PCD–Present, 60 PCD–Absent).

PAI=Personality Assessment Inventory, NIM=PAI Negative Impression Management scale, WMT=Word Memory Test, PTSD=Posttraumatic Stress Disorder, DEP–Cog=PAI Depression–Cognitive subscale, DEP–Aff=PAI Depression–Affective subscale, and SUI=PAI Suicide scale,

Not possible to calculate the odds ratio when cell=0.

For the effort testing and validity factors, the PCD-Present group was significantly more likely to have scores on the WMT and PAI NIM scale that were suggestive of poor effort and/or exaggerated symptom reporting (OR: range=8.07–18.13; RR: range=2.11–2.30). In contrast, the PCD-Absent group was significantly more likely to have scores on the WMT and PAI NIM scale that were suggestive of adequate effort and unbiased symptom reporting (OR=9.13, RR=2.56).

For the psychological factors, the PCD-Present group was significantly more likely to have elevated scores on the PAI Depression subscales (range: OR=7.34–21.38; RR=2.11–3.59), with the highest values found for the PAI Depression-Affective subscale (OR=21.38, RR=3.59). The PCD-Present group was also significantly more likely to have endorsed symptoms on the PCL-C consistent with diagnostic criteria for “Possible” (OR=18.79; RR=2.93) and “Probable” PTSD (OR=18.50; RR=2.71). When the depression and PTSD criteria were combined, there was an overall increase in all OR and RR values. The PCD-Present group was significantly more likely to have elevated scores on one of the PAI Depression subscales and/or meet diagnostic criteria for PTSD (range: OR=15.97–39.33; RR=2.40–3.95).

The results of effort and validity testing were strongly related to screening positive for PCD, depression, and PTSD, singly and in combination. In the total sample, failure occurred in 41.6% effort or validity testing (i.e., patients failed the Word Memory Test or had a PAI NIM T-score of 70 or greater). If a patient did not meet criteria for any diagnosis (i.e., PCD, PTSD, or depression), the failure rate was only 11.1%. The failure rate in those meeting criteria for a diagnosis, however, was 64.6%, 76.5%, and 73.2% for PCD, depression, and PTSD, respectively. The failure rate for those who met criteria for any one of the three diagnoses was 64.8%; for those meeting criteria for two diagnoses, it was 72.1%; and for those meeting criteria for all three diagnoses, it was 80.8%.

Discussion

The purpose of this study was to identify factors that are predictive of PCD symptom reporting after TBI in U.S. military service members. A total of 19 factors were examined, including demographic characteristics, injury-related variables, and psychological and effort testing measures. It was hypothesized that demographic characteristics and injury-related variables would have a weak association with, and would not be predictive of, PCD symptom reporting. It was further hypothesized that psychological and effort testing factors would be highly associated with, and predictive of, PCD symptom reporting. Overall, the results largely support these hypotheses, with some exceptions.

Consistent with the first hypothesis, service members who met modified DSM-IV diagnostic criteria for PCD did not differ on the vast majority of demographic and injury-related variables when compared with service members who did not meet diagnostic criteria for PCD (i.e., age, sex, education, race, estimated premorbid intellectual ability, number of deployments at the time of injury, combat versus non-combat related injury, or mechanism of injury).

Inconsistent with the first hypotheses, however, some differences were noted on factors relating to TBI severity, body injury severity, and the time tested post-injury. Participants who had less severe body injuries and/or less severe brain injury had a greater risk for meeting diagnostic criteria for PCD. That is, more serious bodily injuries and more serious brain injuries were associated with lower, not increased, risk for PCD. Results relating to body injury severity are consistent with previous research that has also found that the presence of serious body injury is associated with lower symptom reporting in U.S. military service members.^84,85 French and colleagues⁸⁵ illustrated an inverse severity-response relation between body injury severity and symptom reporting on the PCL-C and NSI. That is, greater body injury severity was associated with lower PCD symptom and traumatic stress symptom reporting.

With regard to time tested after injury, participants who were tested more than 12 months post-injury were more likely to meet PCD diagnostic criteria than those participants evaluated within the first few months. Given the known relation between PCD, PTSD, and depression in a military population,^{14,51,52,57,58,86,87} it is possible that these findings reflect, in part, the tendency for mental health problems to intensify with time.^59

–62 For example, in a sample of service members returning from Iraq, Millikin and coworkers⁶¹ found that less mental health distress was reported by service members immediately on return from deployment compared with 4–10 months later.

Despite this possibility, however, it is considered more likely that these results reflect a sample selection bias. Patients who were seen at WRAMC for a TBI evaluation many months after injury are typically symptomatic. They are referred to the hospital for this reason. As such, there would be very few people who are referred to the hospital because of a remote TBI who are not symptomatic. In contrast, most of those patients who were evaluated at WRAMC within the first few months post-injury were medically evacuated from combat theater and were treated at the hospital soon after injury. As such, some of these patients were highly symptomatic whereas others were not.

Consistent with the second hypothesis, and also consistent with previous research,^38

–41,88 PCD symptom reporting was strongly associated with possible symptom exaggeration and poor effort. More than half of those whose screening results were positive for PCD experienced failure in effort testing (55.4%), compared with a 13.3% effort test failure rate in those who did not meet criteria for PCD. Considered differently, effort test failure is a risk factor for positive screening results for PCD in that 81.8% of those in whom effort testing failed were in the PCD-Present group. Approximately one-third of those who had positive screening results for PCD (32.3%) had elevated scores on the PAI NIM scale (T of 70 or greater), compared with only 3.3% of those who did not meet criteria for PCD having elevated validity scores. Considered differently, possible symptom exaggeration is a risk factor for positive screening results for PCD in that 91.3% of those with elevated validity scores were in the PCD present group. The rate of failing effort or validity testing was 64.6%, 76.5%, and 73.2%, in those with positive screening results for PCD, depression, or PTSD, respectively. The rates of effort or validity test failure were even higher in those meeting criteria for all three diagnoses (i.e., 80.8%, respectively).

Of course, when effort and validity issues are identified, it would be a mistake to conclude uncritically that the person has accurately reported symptoms and meets criteria for a diagnosis of PCD (or PTSD or depression). Rather, it would be more reasonable to conclude that the person has either (1) exaggerated the severity of legitimate PCD symptoms, (2) exaggerated the presence of PCD symptoms, or (3) both.

Also consistent with the second hypothesis, depression and traumatic stress symptoms were strongly associated with postconcussion symptom reporting. Depression and PTSD symptoms alone accounted for more than half of the variance in the prediction of NSI total scores. Of those with PCD, 73.8% had elevated Depression-Affective subscale scores compared with 11.7% of those without PCD having elevated scores. Considered differently, of those who had elevated scores on the PAI Affective subscale for depression, 87% met criteria for PCD. Similarly, of those who met criteria for probable PTSD, 90% met criteria for PCD. PCD rarely occurred in the absence of depression or PTSD symptoms, with only 9.6% (n=12) meeting criteria for PCD but not having an elevated depression scale or meeting diagnostic criteria for PTSD (“Possible” or “Probable” PTSD). When all four factors are combined, only 5.6% (n=7) of the total sample had PCD in the absence of depression, PTSD, possible symptom exaggeration, and poor effort (“Possible” or “Probable” PTSD).

The strong relations between PTSD, depression, and PCD in this study are consistent with other studies in both military and civilian populations. Past studies have found that PTSD and depression largely explain the relationship between a history of MTBI and PCS reporting, along with other general health symptoms.^51,52,57,86 Cooper and associates⁸⁷ found that MTBI patients with high levels of PTSD reported significantly more PCD symptoms than those reporting low levels of PTSD. Brenner and colleagues⁵⁸ found that those with MTBI alone or PTSD alone had greater postconcussion symptom reporting than those with neither diagnosis.

A diagnosis of both MTBI and PTSD was more strongly associated with postconcussion symptom reporting than either MTBI alone or PTSD alone. In a sample of civilian MTBI patients and non-brain injured trauma controls, acute traumatic stress within 14 days post-injury was a significant predictor of PCS diagnosis at 3 months, regardless of MTBI. Moreover, PTSD at 3 months after injury was more strongly associated with PCD diagnosis than acute traumatic stress, indicating that the severity of traumatic stress symptoms and PCD strengthened over time.¹⁴ The influence of depression on PCD reporting is also well documented in civilian populations,^31,89 but not in military populations.

Limitations

This study has several methodological limitations. First, this was a sample of convenience. Although we evaluated the influence of multiple factors on PCD symptom reporting, we were restricted to the factors that were available in the database. There are other known factors⁹⁰ that could not be included here (e.g., social psychological factors such as symptom attribution, diagnosis threat, and good-old-days bias). Second, the timing of the collection of outcome measures at WRAMC was influenced by clinical and administrative factors. This resulted in a number of subjects from the larger sample not meeting inclusion criteria. Third, information regarding compensation status or external incentives was not available in this sample. Although it is common for service members to have external incentives at the time of testing (e.g., avoiding being deployed again, obtaining a disability pension, or other financial incentive), this information was not available, and we could not evaluate the influence of external incentives on symptom reporting.

Conclusion

The results from this study identified six predictors of PCD symptom reporting. There are four primary conclusions to draw from these results. First, more serious body injuries and more serious brain injuries were associated with lower, not increased, risk for meeting PCD diagnostic criteria. Second, the presence of depression, traumatic stress, or both was strongly associated with PCD symptom reporting and with diagnostic criteria for PCD. Third, possible symptom exaggeration and poor effort were strongly associated with PCD symptom reporting and increased risk for possible false positive diagnoses of PCD. Fourth, in the present sample, symptom reporting that met diagnostic criteria for PCD rarely occurred in the absence of depression, traumatic stress, symptom exaggeration, or poor effort. Only seven (5.6%) of the 125 participants in this study reported symptoms that met diagnostic criteria for PCD in the absence of one of these four factors.

Overall, these results once again highlight the need for the careful differential diagnosis of PCD. Clinicians cannot assume uncritically that endorsement of items on a symptom checklist is indicative of PCD. There are many factors that can cause, maintain, or mimic self-reported PCD symptoms—and PCD is best considered a diagnosis of exclusion.

Footnotes

Acknowledgments

Portions of these data were presented at the International Neuropsychological Society annual conference, Montreal, Quebec, Canada, February 2012.

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, Army, or Air Force; the Department of Defense; or the U.S. Government.

Author Disclosure Statement

No competing financial interests exist.

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