NEUROCOGNITIVE VARIABLES UNDERLYING GROUP PERFORMANCE ON A MEASURE OF EFFORT: THE MEDICAL SYMPTOM VALIDITY TEST (MSVT) Julie Hart Covert, M.S.

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1 NEUROCOGNITIVE VARIABLES UNDERLYING GROUP PERFORMANCE ON A MEASURE OF EFFORT: THE MEDICAL SYMPTOM VALIDITY TEST (MSVT) Julie Hart Covert, M.S. Dissertation Prepared for the Degree of DOCTOR OF PHILOSOPHY UNIVERSITY OF NORTH TEXAS December 2008 APPROVED: Susan Franks, Chair James Hall, Committee Member Frank Collins, Committee Member Rodney Isom, Committee Member Michael Walker, Committee Member Linda Marshall, Chair of the Department of Psychology Sandra L. Terrell, Dean of the Robert B. Toulouse School of Graduate Studies

2 Covert, Julie Hart. Neurocognitive Variables Underlying Group Performance on a Measure of Effort: The Medical Symptom Validity Test (MSVT). Doctor of Philosophy (Health Psychology and Behavioral Medicine), December 2008, 88 pp., 31 tables, 2 figures, references, 92 titles. This study utilized the Medical Symptom Validity Test (MSVT) and a set of standard neuropsychological instruments to determine the underlying construct of the MSVT that accounts for effort in mild traumatic brain injury (mtbi) patients by comparing/contrasting mtbi with dementia and an analog simulation. The results indicate that a common underlying neurocognitive construct (memory) exists between mtbi and dementia patients, which may account for poor effort as measured by the MSVT. Other underlying factors emerged for both groups, though they did not point to a common construct. This finding suggests that the overall effect of brain injury in neurologically impaired groups also impacts effort performance as measured by the MSVT. Similarly impaired performance patterns also emerged between mtbi and dementia groups in sub-groups that failed effort measures. Thus, failed effort tests may be a function of more pronounced deficits in these groups, rather than a function of effort. Finally, although similar effort profiles were noted between mtbi and analog simulators, the analog group was unable to mimic the neurocognitive effects of mtbi.

3 Copyright 2008 By Julie Hart Covert ii

4 ACKNOWLEDGEMENTS I sincerely thank my committee members for their time and efforts in helping me finish this work. I am particularly grateful to Susan Franks, Ph.D., who has been both a mentor and a friend. Her unwavering support throughout my educational career will never be forgotten. I wish to thank James Hall, Ph.D. for his contribution to this study as well as for repeatedly going above and beyond to ensure my success in this program. I wish to express my sincerest appreciation to Mike Walker, Ed.D. for his exceptional wisdom and guidance. I would also like to thank Rodney Isom, Ph.D. for his humor, patience, and the insight that he has brought to this study. I would like to thank my friends and family for their love and endless encouragement which have allowed me the strength to pursue my endeavors. I express particular gratitude to my colleagues, Scott Hilborn, Ph.D. and Susan Frensley, Ph.D., for their friendship and infinite support. I would not be here today without them. I also would like to acknowledge those individuals who assisted with this project, especially Bruce Jones, Ph.D., Michelle Harvey, Ph.D., and April Wiechmann. Finally, I offer my deepest appreciation to my husband, Chris, for his constant love and never-ending belief in me. iii

5 TABLE OF CONTENTS Page ACKNOWLEDGEMENTS...iii LIST OF TABLES... v Chapters I. INTRODUCTION... 1 Malingering vs. Effort Effort Defined Evaluation of Effort Symptom Validity Tests Traumatic Brain Injury (TBI) Traumatic Brain Injury and Effort Analog Design Dementia Dementia and Effort Rationale for Study Hypotheses II. METHOD Participants Measures Psychometric Properties of the Test Battery Statistical Methodology III. RESULTS IV. DISCUSSION Limitations of the Study Recommendations for Future Research Implications REFERENCES iv

6 LIST OF TABLES Page 1. Effort Measure (MSVT) Demographic Variable Summary (mtbi) Demographic Variable Summary (Dementia) Demographic Variable Summary (Analog) Neuropsychological Measures Independent Variable Summary (mtbi) Independent Variable Summary (Dementia) Independent Variable Summary (Analog) Dependent Variable Summary (mtbi) Dependent Variable Summary (Dementia) Dependent Variable Summary (Analog) Mean Score Comparisons by Group (Overall) Mean Score Comparisons by Group (pass/fail effort: mtbi/dementia) Mean Score Comparisons by Group (pass/fail effort: mtbi/analog) Intercorrelations Among Variables Intercorrelations Among Variables Intercorrelations Among Variables Intercorrelations Among Variables Intercorrelations Among Variables Intercorrelations Among Variables Intercorrelations Among Variables Intercorrelations Among Variables v

7 23. Intercorrelations Among Variables Regression Analysis - Immediate Recognition (Effort)/mTBI Regression Analysis - Consistency (Effort)/mTBI Regression Analysis - Paired Associates (Effort)/mTBI Regression Analysis - Free (Effort) Recall/mTBI Regression Analysis - Immediate Recognition (Effort)/Dementia Regression Analysis - Consistency (Effort)/Dementia Regression Analysis - Paired Associates (Effort)/Dementia Regression Analysis - Free (Effort)/Dementia vi

8 LIST OF FIGURES Page 1. Mean effort subtest scores across groups failing effort Mean effort subtest scores across groups passing effort vii

9 CHAPTER I INTRODUCTION Neuropsychological assessment is designed to yield identifiable measures of outcome related to cognitive functioning. Collection of neuropsychological test data requires patient cooperation in the form of symptom report and test performance. Accurate identification of deficits and subsequent diagnosis and treatment planning is thereby dependent on optimal effort on behalf of the participant. Clinicians are accountable for determining the validity of the information and test data obtained from the patient during neuropsychological evaluation ((Bush, Ruff, Troster, Barth, Koffler, Pliskin, Reynolds & Silver, 2005). The issue of effortful patient performance has been a factor in neuropsychological assessment for a number of years. However, over the course of the last two decades, clinical interest in the topic of symptom exaggeration/malingering or feigning/sub-optimal effort has steadily increased by in large because of an overall increase in worker s compensation claims, injury-related lawsuits and/or insanity defense pleas (Lynch, 2004). Due to these types of incentives, or secondary gain, the issue of whether or not a patient is compliant with testing, or putting forth good effort, is critical to the overall evaluation of neuropsychological symptoms. One issue that confounds the determination of optimal performance is the lack of any operational definition in the psychological community when referring to this construct (Bush et al., 2005). The research is widely inconsistent when referring to the phenomenon, with labels ranging from malingering to symptom invalidity to effort, to 1

10 name a few. Although no consensus yet exists, many neuropsychologists currently use the term effort to describe patient motivation towards testing (Demakis, et al., 2001). Clinicians have evaluated insufficient effort in a number of ways. Originally, neuropsychologists evaluated effort based on subjective clinical opinions (Green, Rohling, Lees-Haley, & Allen, 2001), which focused on inconsistent responding during testing or between patient report and observed behavior/test results. Although initially generally accepted in the neuropsychological community, current practice is restricted due to reported low incidence of invalidity signs and considerable overlap between valid and invalid symptoms (Franzen, Iverson & McCracken, 1990; Trueblood & Schmidt, 1993). Difficulty identifying performance patterns has led investigators to the development of specific tests for detection of effortful performance. Known as symptom validity tests, or SVTs (Iverson & Binder, 2000; Iverson, et al., 2002; Slick, Sherman, & Iverson, 1999; Slick, Tan, Strauss, & Hultsch, 2004; Tombaugh, 1997), these measures have become the standard of practice for effort evaluation in the neuropsychological community (Slick et al., 2004). One group consistently evaluated for effort is mild traumatic brain injury (mtbi) patients. Approximately 85% of all traumatic brain injuries in the Untied States are classified as mild (Bazarian, McClung, Shah, Cheng, Flesher & Kraus, 2005). The most common neurocognitive deficits associated with mild TBI include poor attention and concentration, memory, and decreased processing speed (Frencham, Fox & Maybery, 2005). The prevailing consensus is that these deficits are acute, with a majority of 2

11 patients recovering in one to three months, thus having no neurological basis for ongoing symptoms (Binder, 1997; Binder, Rohling & Larrabee, 1997). Some studies dispute the above-mentioned findings. Alexander (1995) reported that 10-15% of mtbi patients do have ongoing deficits indicative of significant brain impairment. Other studies have also reported long-term impairment associated with mtbi in the areas of processing speed (Bernstein, 2002), sustained attention (Bohnen, Jolles, Twijnstra, Mellink, & Wijnen, 1995), memory (Frencham et al., 2005), divided attention and rapid processing (Cicerone, 1997; Mangels, Craik, Levine, Schwartz, & Strauss, 2002). Additionally, Frencham et al. (2005) noted several methodological concerns that should be addressed, all of which may contribute to the belief that mtbi patients sustain only acute and insignificant injuries. This belief has led to an abundance of research devoted to testing effort in this population. For example, Binder (1993) and Binder and Kelly (1996) reported that approximately 30% of mtbi patients involved in compensation claims exaggerated deficits in neurocognitive testing. Other studies report commensurate findings. Millis (1992) found a superiority of test scores in patients with documented severe traumatic brain injury versus those with mtbi. Similar findings were made by Green and Iverson (2001) and Green (2004). Few studies have examined effort scores in relation to actual measures of neurocognitive ability in this population. Green et al. (2001) reported that mtbi groups showed significantly higher failure rates on a test of effort than groups with more severe documented brain injuries. When the authors compared effort scores to overall 3

12 neurocognitive performance, they found that the mtbi group failing effort testing scored significantly worse on the test battery than more severely impaired patients. The authors interpreted these results to mean that effort has a greater effect on test scores than severity of injury. Studies have also utilized analog designs to examine effort in comparison to mtbi. Beetar and Williams (1995) distinguished a pattern of performance between analog simulators and amnesic patients with severe memory impairments, whereby simulators performed better on recall measures (harder task) than on recognition measures (easier task). Green (2003) reported a similar simulator pattern whereby mildly head injured patients who failed a test of effort performed similarly to the analog group. Only one study has examined group differences using neurocognitive measures versus tests of effort to discern whether or not a simulator pattern exists between analog participants and mtbi patients performance on neuropsychological tests. Results showed the analog participants were unable to perform like the TBI comparison group on neuropsychological measures (Schwartz, Gramling, Kerr, and Morin, 1998). The only other population that performs as poorly as mtbi patients on measures of effort and neurocognitive function is dementia populations (Green, 2004). Although neurocognitive deficits in demented populations are more severe, their deficit profile is reportedly similar to those of TBI patients (Hinkebein, Martin, Callahan and Johnstone, 2003). On tests of effort, demented patients have also scored poorly, with 4

13 approximately 50-80% failing these measures on a consistent basis (Green, 2003; Teichner & Wagner, 2004) as compared to 30% failure estimates for mtbi patients. Even though demented patients perform poorly on tests of effort, they are presumed to fail due to extreme memory deficits, rather than lack of motivation to do well (Green, 2004). Due to known cognitive deficits within the demented population, and the simulator pattern exhibited by analog participants, researchers have inferred that the poor performance SVTs exhibited by approximately one third of the mtbi population is due to poor effort, rather than any identifiable neurocognitive variable. Some researchers hypothesize that methodological issues in the research literature may artificially contribute to the misclassification of mtbi patients with true, chronic cognitive deficits as individuals exhibiting poor effort. (Frencham et al., 2005; Reitan and Wolfson, 1999) The current study will address these issues in an attempt to better understand how these methodological factors may influence the classification of some mtbi patients as exhibiting poor effort. Additionally, although research has shown mtbi patients who fail effort tests also perform below expected levels on neuropsychological tests, no studies have addressed specific test performance in relation to measures of effort. The present study will examine neurocognitive variables within and between groups on a test of effort to discern whether any underlying variables contribute to group performance. Also, no studies have compared mtbi cognitive performance to dementia patient performance despite the fact that evidence has shown the two groups have similar neurocognitive deficit profiles, as well as similar effort test performance. The current 5

14 analysis will compare performance between these groups on the specified measures of interest. Finally, evidence has been presented to illustrate a simulator pattern on effort tests; however, research does not currently support a simulator pattern in neurocognitive test performance. The current investigation will examine test performance between groups (analog simulators vs. mtbi) to identify whether or not such a pattern does exist. Malingering vs. Effort Despite growing interest in the topic, and obvious need for the detection of optimal effort, there is no consensus or operational definition in the literature regarding the differentiation of valid from invalid test performance (Bush et al., 2005; Slick et al., 1999). In fact, Inman, Vickery, Berry, Lamb, Edwards & Smith (1998) assert that the true base rates of sub-optimal effort during neuropsychological evaluation cannot be fully distinguished, partly due to inconsistent definitions of the construct. Available research addressing the underlying issue of effort in test performance utilizes a variety of terms in relation to insufficient test responding including: malingering (Beetar & Williams, 1995; Dunn, Shear, Howe & Ris, 2003; Green, Iverson & Allen, 1999; Green et al., 2001; Hartman, 2002; Hilsabeck, LeCompte, Marks & Grafman, 2001; Iverson & Binder, 2000; Lynch, 2004; Iverson, Lange, Green & Franzen, 2002; Slick, et al., 2004; Teichner & Wagner, 2004), effort or suspect effort (Constantinou, Bauer, Ashendorf, Fisher & McCaffrey, 2005; Lynch, 2004; Nelson, Boone, Dueck, Wagener, Lu & Grills, 2003), exaggeration or symptom exaggeration 6

15 (Iverson & Binder, 2000; Lynch, 2004; Richman, Green, Gervais, Flaro, Merten, Brockhaus & Ranks, 2005), and symptom validity (Merten, Green, Henry, Blaskewitz & Brockhaus, 2005; Rohling, Green, Allen & Iverson, 2002). This lack of consensus is not only confusing to the reader, but can result in difficulty with diagnosis and misunderstanding or mislabeling on behalf of other interested parties, such as attorneys, insurance companies, physicians, and compensation boards. Consequently, it is essential that an operational definition be assigned this phenomenon, as there are distinct differences and connotations associated with these variable designations (Sweet, Wolfe, Sattleberger, Numan, Rosenfeld, Clingreman, & Nies, 2000). An abundance of literature refers to lower-than-expected test performance as malingering. The DSM-IV TR (American Psychiatric Association, 2000) includes malingering as a V code (V65.2) and offers the following definition: the intentional production of false or grossly exaggerated physical or psychological symptoms motivated by external incentives such as avoiding military duty, work, obtaining financial compensation, evading criminal prosecution, or obtaining drugs (p. 683). The manual advises that malingering should be considered if any combination of the following is observed (American Psychiatric Association, 2000): 1. The subject is referred by an attorney for examination. 2. There is considerable discrepancy between claimed stress or disability and objective examination findings. 7

16 3. There is lack of cooperation during the evaluation and in complying with any prescribed treatment. 4. The presence of an antisocial personality disorder. Although patients presenting for neuropsychological evaluation frequently meet one or more of these criteria, clinicians are often reticent to diagnose malingering, which is widely considered pejorative (Iverson & Binder, 2000) and can result in significant physical and financial consequences for the patient in the event of a false-positive diagnostic error (Slick et al., 1999). In recent years, many experts have agreed that the term malingering may be inappropriately applied in some patient populations (Demakis, Sweet, Sawyer, Moulthrop, Nies, & Clingerman, 2001; Slick, Sherman, & Iverson, 1999). Slick and colleagues (1999) define malingering as the volitional exaggeration or fabrication of cognitive dysfunction for the purpose of obtaining substantial material gain, or avoiding or escaping formal duty or responsibility (p.552). The authors note that to assign a diagnosis of malingering, the individual cannot be deemed to have diminished capacity (which can be the case with psychological or neurocognitive disorders), or a differential diagnosis (such as factitious disorder). Additionally, there must be unmistakable evidence of rational and judicious exaggeration or feigning of cognitive impairment. As such, the authors identify that malingering is differentiated from apparently similar presentations that are not contingent on volition toward discernable secondary gain. These types of responses include, poor or inconsistent effort, defensive, hostile or oppositional approaches to test taking that result from fatigue, psychiatric disturbance, 8

17 and legitimate neurological impairment (p. 546). Iverson (2000) further asserts that the existence of symptom exaggeration or sub-optimal effort should not routinely be associated with malingering. Iverson and Binder (2000) state that the intentional exaggeration of symptoms or purposeful poor performance during testing is negative response bias, not malingering. The authors assert that negative response bias describes behavior, but not motivation. To diagnose malingering, they say, the clinician must infer motivation. This assignment of motive, or intent to achieve some external goal, is virtually impossible to discern in the absence of any identifiable proof (e.g., patient admission) or knowledge otherwise (Slick, et al., 1999). In their NAN position paper, Bush and colleagues (2005) defined response bias as, an attempt to mislead the examiner through inaccurate or incomplete responses or effort (p. 420). This definition also does not infer motive. In the present investigation, the term malingering will not be utilized in regards to assessment of performance because we have not yet identified whether poor performance is due to other variables. Effort Defined Recently, clinicians have begun to use the term effort to describe patient motivation to perform well during assessment (Demakis et al., 2001). If inconsistent or sub-optimal effort is suspected, results may be considered invalid (without specific designation toward psychopathology, malingering, etc). Bush and colleagues (2005) defined effort as the investment in performing at capacity levels this term refers to an examinee s effort to perform well (p. 420). The 9

18 authors note that this definition is often not specified in discussions of effort testing. Sweet et al. (2000) proposed a more comprehensive definition, describing insufficient effort as a degree of effort that reaches a meaningful clinical threshold of being incomplete or partial and is significantly worse than performance standards known to reflect genuine neurological disorder (p.107). Moreover, they note that insufficient effort may or may not be purposeful. When insufficient effort is purposeful and related to gain, that is malingering. In sum, effort is a more general term than malingering and when evaluated, can help identify valid from invalid performance, without necessarily inferring motive. Thus, for the purposes of the current analysis, Sweet et al s (2000) characterization will serve as the working definition for insufficient effort when referring to behavior. Evaluation of Effort Traditionally, neuropsychologists have evaluated effort based on subjective clinical opinions (Green, et al., 2001). In doing so, the focus of attention is an inconsistent response pattern, which can take many forms. One type of inconsistency relates to reported symptoms and observed behavior. An example of this type of behavior would include a patient reporting that he or she has severe physical deficits related to injury, but is observed engaging in extreme physical activity. Another type of inconsistency can be observed between behavior (during interview) and test performance. For example, the patient may report severe deficits with attention/concentration and memory, perform poorly on corresponding test measures, 10

19 but attend to and provide detailed information and social history during the clinical interview. Other types of inconsistencies exist in the context of text performance (Iverson & Binder, 2000). These include discrepancies between tests presuming to measure the same construct (e.g., auditory attention); discrepancies between actual and expected test performance based on premorbid history and injury severity; and, consistency between evaluations (e.g., performance should not decline upon re-evaluation due to symptom recovery, practice effects, etc.). Reviewing data in this manner is often referred to as the pattern of performance method (Slick, et al., 1999). Review of pattern of performance, or inconsistency methods, reflect mixed results in their ability to distinguish between effortful and sub-effortful performance (Bernard, 1990; Faust & Guilmette, 1990). Further, Tombaugh (1997) reports that although the practice of analyzing inconsistent response patterns has been widely accepted in the neuropsychological community it has been restricted due to low incidence of invalidity signs and considerable overlap between valid and invalid symptoms (Franzen, et al., 1990; Trueblood & Schmidt, 1993). Symptom Validity Tests Difficulty associated with identification of performance patterns has led investigators to develop specific tests or procedures designed to detect aspects of effortful performance. These tests are widely referred to as symptom validity tests, or SVTs (Iverson & Binder, 2000; Iverson, et al., 2002; Slick, et al., 1999; Slick et al., 2004; Tombaugh, 1997). In practice, SVTs use probability analysis to assess patient 11

20 performance on a forced-choice test. Originally, reports indicated that random responses and those below chance levels, were indicative of poor effort (Tombaugh, 1997); however; more recent studies have indicated that poor effort can be evident in scores reflecting greater than chance accuracy (Gervais, Rohling, Green & Ford, 2004; Green, et al., 1999; Green et al., 2001; Hartman, 2002; Tombaugh, 1997). Even though some patients scored greater than chance, results were still significantly below scores obtained by standardized comparison groups like brain injured, demented, mentally retarded, or neurologically intact individuals. Consequently, detection of poor effort with Symptom Validity Testing has come to rely on norm-based criteria including scores falling below that of a significantly impaired group (e.g., severely brain injured) or scores falling below a specific confidence interval (typically 90%) (Slick, et al.,1999). Review of SVT literature reveals mixed results regarding the tests ability to appropriately identify poor effort (Hartman; 2001; Iverson & Binder, 2000; Lynch, 2004; Slick et al., 2004). Specifically, various individual SVTs have been criticized for possessing poor predictive validity, as well as poor specificity and sensitivity. In choosing a strong effort test, Lynch (2004) suggests selecting tests with both specificity and sensitivity, meaning the test measures willingness to put forth basic effort (specificity) and is not sensitive to the neurocognitive dysfunction of interest (sensitivity). Other suggestions include: good face validity; measures deficits likely to be exaggerated by patients claiming that specific injury (e.g., poor memory with brain damage); have a strong normative basis; are based on validation studies that include controls, patient populations, and persons suspected of or known to put forth poor 12

21 effort in clinical assessment conditions; are difficult to fake or coach; are easy to administer; and, are supported by continuing research (Hartman, 2002). Several SVTs have been well validated and appear to meet the above-mentioned criteria, including the Word Memory Test (Green, Allen & Astner, 1996), Computerized Assessment of Response Bias (CARB; Allen, Conder, & Green; 1997), Recognition Memory Test (Warrington, 1994), and the Medical Symptom Validity Test (MSVT; Green, 2004). These, and other measures, have become widely accepted for use in the neuropsychological community. In a survey of expert s practices, Slick et al., (2004) reported that 79% of responding neuropsychologists used at least one SVT as a measure of effort in their test batteries. Populations commonly administered SVTs as part of a neuropsychological battery include: severe and mild TBI, Chronic Pain and/or Worker s Compensation, Chronic Disease (e.g., cancer, dementia, Alzheimer s, CVA, cardiovascular, etc), and psychologically disordered. Traumatic Brain Injury A traumatic brain injury (TBI) typically results from an object s forceful impact on an individual s skull causing either temporary or permanent damage to physical, cognitive, or psychosocial functions. The insult is usually accompanied by an altered or diminished state of consciousness (Dawodu, 2008). Traumatic brain injury can result in widespread damage due to the way in which the brain ricochets inside the skull upon impact, causing diffuse axonal shearing or focal deficits. Due to its large size and its 13

22 location at the front of the skull, the frontal lobe region is widely considered the area of the brain most frequently affected by traumatic brain injury. The symptoms of TBI are classified from mild to moderate to severe. Classification is dependant on the extent of the damage. Adolescents and young adults (ages 15-24) and older adults (ages 65+) are at the highest risk for sustaining a traumatic brain injury. The leading causes of TBI include motor vehicle accidents (MVAs), falls, recreational or sports activities and firearms (Thurman, 2001). Cognitive deficits most often associated with traumatic brain injury include impairments in cognitive flexibility, speed of information processing, attention and memory (mild to moderate), and mild deficits in IQ noted in the acute phase (Hinkebein, et al., 2003). Of the estimated 1.5 million head injuries sustained annually in the U.S., nearly 1.3 million are categorized as mild (Bazarian, et al., 2005). Clinically defined, mild TBI (mtbi) or mild head injury (MHI) involves loss of consciousness for less than 30 minutes, or Glasgow Coma Scale (GCS) score of 13-15, no skull fracture on physical examination and a nonfocal neurologic exam (Green, et al., 2001; Kay et al., 1998). The Glasgow Coma Scale defines the severity of TBI within 48 hours of insult and relies on verbal and motor response as well as eye opening. Scores range from a 3-15, with 3 indicating the most severe score (deep coma) and 15 the highest possible score (Dawodu, 2008). Symptoms hallmark of mtbi include immediate retro or anterograde amnesia and a concurrent alteration in consciousness. Longer-term ramifications of mtbi often include one or more of the following: fatigue; head, back, and neck pain (including 14

23 headaches); general confusion and other cognitive problems (decreased attention/concentration, poor memory, slowed speed of processing, decreased verbal fluency); and emotional lability. Frencham et al. (2005) report the most common neurocognitive deficits associated with mild TBI to include poor attention and concentration, memory, and decreased processing speed. Researchers and clinicians generally concur that these deficits are not long-term, with a vast majority of patients showing full recovery in three months or less (Binder, 1997; Binder et al., 1997), thereby having no neurological basis for ongoing symptoms. In fact, in Binder and his colleagues' review (1997), the authors stated that it can be argued that the average effect of mild head trauma [MHT] on neuropsychological performance is undetectable (p. 428). While several studies have found the above mentioned effects of mtbi to be acute, evidence exists to the contrary. Although Binder s (1997) general consensus is one of negligible effects, he did report in his meta-analysis that approximately 8% of mtbi patients remained chronically symptomatic, with 14% occupationally disabled. Similarly, Alexander (1995) reported that 10-15% of mtbi patients do have ongoing deficits indicative of significant brain impairment. Other studies have also reported longterm impairment associated with mtbi in the areas of processing speed (Bernstein, 2002), sustained attention (Bohnen, et al., 1995), memory (Frencham et al., 2005) and divided attention and rapid processing (Cicerone, 1997; Mangels, et al., 2002). Reitan and Wolfson (1999) conducted a study in which they examined individuals with mtbi who had persisting clinical complaints. They found that 75% of these 15

24 patients showed significant ongoing neuropsychological deficits not believed to be related to psychiatric problems, malingering, or invalid test performance. These patients also showed significantly more impairment than persons with mtbi admitted into a research (i.e., as opposed to a clinical) study. Frencham et al. (2005) conducted a meta-analysis of neuropsychological studies of mtbi. While the authors reiterated previous findings noting the short-term nature of a majority of mtbi impairments, they noted several methodological concerns which may contribute to the widespread suspicion of more chronic mtbi symptoms. First, time since injury has not been adequately addressed in the literature, despite the authors finding that time since injury accounts for 22% of the variance in the overall effect of mtbi. While they noted that effect size for cognitive domains did tend toward zero with increased time since injury (with the exception of memory), they also conceded that a more severely cognitively impaired sub-sample of this population may exist, with significant information lost due to pooled data. Second, Frencham and colleagues also noted that only five-studies over the past eight years have addressed the post-acute stage of mtbi, with even fewer studies addressing outcome more than 6 months post-injury. Third, the authors report that prospective recruitment of patients may also affect outcomes, as also suggested by Reitan and Wolfson (1999) and Binder (1997). Finally, Frenchman et al. (2005) agreed with Bernstein (1999) and Cicerone s (1997) report that studies using general measures of neurocognitive function may not be sensitive to more subtle deficits of mtbi, resulting in patients appearing neurologically intact despite significant cognitive impairment. These factors represent 16

25 significant concerns regarding the assumption that patients with mtbi are suspect with regards to complaints of significant, ongoing cognitive deficits. Traumatic Brain Injury and Effort This controversy over the acute and chronic effects of mtbi in conjunction with a reported increase in legal claims following head trauma (Pankratz & Binder, 1997) has resulted in heightened attention for this population with respect to effort during testing (Beetar & Williams, 1995; Binder, 1993; Constantinou, et al., 2005; Dunn et al., 2003; Green et al., 1999; Green et al., 2001; Larrabee, 2000; Hartman, 2002; Hilsabeck, et al., 2001; Iverson et al., 2002; Lynch, 2004; and Nelson, et al., 2003). Research results are discrepant with respect to insufficient effort base rates. Trueblood and Schmidt (1993) reported poor motivation in 15% of their outpatient sample of mildly brain injured patients, while Binder (1993) and Binder and Kelly (1996) reported approximately 30% of mtbi patients involved in compensation claims exaggerated deficits in neurocognitive testing. Greiffenstein, Baker and Gola (1994) reported exaggerated memory deficits in the range of 33-60% (of patients claiming Post-Concussion Syndrome). Larrabee (2000) reported that exaggeration of cognitive deficits in mtbi patients involved in compensation claims was 10 times higher than base rates for true cognitive deficits. Millis (1992) and Millis and Putnam (1994) used the Warrington Recognition Memory Test (Warrington, 1984) to assess effort in mtbi patients involved in head injury litigation. They found a superiority of test scores in patients with documented severe traumatic brain injury versus those with mtbi. Green and Iverson (2001) 17

26 reported similar results using the Computerized Assessment of Response Bias (CARB) in testing effort of mtbi in head-injury/litigation patients. Additionally, Green (2004) reported mean Medical Symptom Validity Test (MSVT) effort scores were lower in mtbi patients failing effort tests than in more severely head injured patients failing effort tests. Green, Iverson & Allen (1999) used the Word Memory Test (WMT) and the Computerized Assessment of Response Bias (CARB) to examine effort in a large sample of TBI patients involved in litigation. They also reported a pattern of superiority of effort test scores in patients with moderate to severe TBI as compared to mtbi patients across both tests. While several studies have examined effort with respect to mtbi, few studies have examined effort scores in relation to actual measures of neurocognitive ability in this population. Green et al. (2001) conducted a study in which they compared effort to neuropsychological test scores in neurological patients (e.g., CVA, aneurysms, MS, tumor, epilepsy, etc), mtbi patients, and moderate to severe TBI patients. All participants were involved in some type of litigation or compensation claim. Two measures of effort, The WMT and the CARB, were given along with a neuropsychological battery consisting of 43 measures of cognitive function. On the WMT, the authors reported a 16% failure rate in the neurological disorder group, and a 33% failure rate in the head injury patients (mtbi and moderate/severe TBI combined). When mtbi and moderate to severe TBI groups were separated, the mtbi group yielded a failure rate of 34% while the moderate to severe group failed the WMT at a rate of 18%. In sum, the mtbi group showed significantly higher failure rates on 18

27 the WMT than either the neurological group or the moderate to severely head injured group (who showed failure rates similar to each other). In comparing effort scores to neurocognitive performance, the authors used an Overall Test Mean Battery (OTMB). Overall Test Mean Battery scores were reported as standard deviations, and moderate to severe TBI groups were combined with the neurological group (TBI-NEURO) and compared to mtbi. When comparing OTBM scores of patients who passed the WMT, the TBI-NEURO group scored as more impaired than the mtbi group. When comparing OTBM scores of TBI-NEURO group who passed the WMT with mtbi group who failed the WMT, the TBI-NEURO group scored significantly better than the mtbi group. In sum, the mtbi group scored significantly worse than the TBI-NEURO group on the OTMB. Though no individual test scores were reported, domain scores for memory, attention and working memory, perceptual organization, psychomotor skills, verbal comprehension, and executive functioning were calculated. Poorer scores were found across domains for the mtbi group that failed the WMT versus moderate to severe TBI group passing the WMT. The most significant differences between groups were found in the memory and attention domains. The authors interpret the results to mean that effort has a greater effect on test scores than severity of injury. Constantinou and colleagues (2005) examined whether performance on a symptom validity test, the Test of Malingered Memory (TOMM; Tombaugh, 1996), could predict generalized poor performance on neuropsychological tests in a group of mtbi litigants. The authors reported that poor performance on the TOMM was significantly 19

28 correlated with poorer performance on the WAIS-R (Weschler, 1981) and the HRNB-A (Reitan & Wolfson, 1993). Additionally, the authors found that patients failing the TOMM (30% of the sample) had lower overall neuropsychological test performance than is expected from mtbi, as well as lower overall test performance as compared to mtbi patients in the study who passed the effort test. Analog Designs Some studies have utilized analog designs to examine incomplete or inconsistent effort in mtbi populations. Analog studies traditionally instruct neurologically normal participants to exaggerate or feign cognitive impairment on standardized measures of effort in order to compare those performances with a known reference group such as brain injured, or normal controls instructed to put forth good effort (Hilsabeck, et al., 2001). Generally, the analog participant is also provided information, such as characteristics of TBI, in order to better simulate impairment. Many simulator studies also instruct participants to attempt to avoid detection of exaggerated deficits. Beetar and Williams (1995) distinguished a pattern of performance between analog simulators and amnesic patients with severe memory impairments, whereby simulators performed better on recall measures (harder task) than on recognition measures (easier task). In Beetar and Williams study, both amnesia patients and neurologically normal individuals score better on recognition measures and worse on recall. Green (2003) reported similar findings when comparing analog simulators to other populations. The author identified a simulator pattern whereby scores on easier recognition tasks were lower than scores on recall tasks. Simulators (all of whom failed 20

29 the WMT) scored worse than dementia patients on easy recognition tasks, while they performed better than dementia patients on harder recall tasks. Mildly head injured patients who failed the WMT showed the same pattern as the analog group, which has been interpreted to mean that this group shows poor effort on testing as opposed to having true cognitive impairment (Green, 2003). While several published studies have utilized standardized neuropsychological tests as measures of effort (Demakis, et al., 2001; DiCarlo, Gfeller, & Oliveri, 2000; Iverson, et al., 2002; Rapport, Farchione, Coleman, & Axelrod, 1998), very few studies were found that compared analog simulators on tests of effort and neurocognitive measures to discern whether or not simulators are able to produce a pattern of neurocognitive deficits consistent with those of mtbi. Only one study examined group differences using neurocognitive measures to assess cognitive performance, rather than using neurocognitive measures to assess effort performance. Schwartz, et al. (1998) presented detailed information about neuropsychological sequelae of TBI to analog participants who were compared to TBI patients on measures of memory and intelligence. Results showed the analog participants were unable to perform like the TBI comparison group on neuropsychological measures. Dementia The most commonly diagnosed forms of dementia include Alzheimer s disease (AD) ad vascular dementia (VaD). Like TBI, dementia is classified as mild, moderate or severe. Alzheimer s disease is a neurodegenerative disorder, while vascular dementia (VaD) is usually the result of cardiovascular disease. Both disorders result in multiple 21

30 cognitive deficits. Despite the differences in etiology, cognitive profiles for both groups are similar, and both groups show progressive cognitive decline. Some evidence exists that greater deficits in verbal fluency and verbal memory have been found in AD patients (Baillon, Muhommad, Marudkar, Surbhatla, Dennis, Spreadsbury, Munro, & Lindesay, 2003). Additionally, cognitive decline is believed to be generally slower and more variable in VaD than AD. Otherwise, neurocognitive deficit profiles routinely show that dementia appears to significantly affect speed of mental processing and cognitive flexibility, followed by memory and then attentional impairments (Crowell, Luis, Vanderploeg, Schinka, & Mullan, 2002; Baillon et al., 2003; Hinkebein et al., 2003). Although deficits in demented populations are more severe, Hinkebein and colleagues (2003) report similar profiles between dementia and TBI. Dementia and Effort Patients with dementia routinely score poorly on measures of effort (Green & Astner, 1996, Green, 2003; Green, 2004; Patton, et al., 2004; Teichner & Wagner, 2004). Teichner and Wagner (2004) reported that individuals with dementia scored significantly poorer on all trials of the TOMM than either normals or cognitively impaired individuals. Green (2004) reported that half of early dementia patients scored below the 85% cut-off in Immediate Recognition (IR), Delayed Recognition (DR) and consistency tasks of the MSVT, while 80% of the advanced dementia patients scored below the cut-off on all three subtests. Green (2003) and Patton et al. (2004) both reported similar findings with the WMT. 22

31 Even though demented patients perform poorly on tests of effort, they are assumed to fail due to extreme memory deficits, rather than lack of motivation to do well (Green, 2004). Also, as Feehan and colleagues (1991) reported demented patients are generally believed to be largely unaware of their cognitive deficits, further accrediting the belief that this group would have no reason to put forth poor effort. The only groups found to perform as poorly as demented patients on effort tests are mtbi and analog simulators (Green 2003; Green, 2004). Due to known cognitive deficits within the demented population, and the simulator pattern exhibited by analog participants, researchers have inferred that the poor performance SVTs exhibited by approximately one third of the mtbi population is due to poor effort, rather than any identifiable neurocognitive variable. Green (2004) states: Once dementia is ruled out, there are very few people indeed, who will score below the 85% cut-off when they are making a full effort to do well. In most cases, people scoring below 90% on the primary effort measures (IR, DR, & consistency) do so because they are not making a full effort to do well on these tests. Alternately, they are trying to do poorly, so that they will appear more impaired than they really are. In either case, the results of the (MSVT) do not reflect the person s actual capabilities and the person s results on other tests are of doubtful validity. Symptom exaggeration is likely. (p. 40). 23

32 Rationale for Study In light of the results presented thus far, it appears logical to conclude that individuals with mtbi show poorer effort as measured by SVTs than groups documented to have severe neurocognitive impairment. Additionally, evidence has been presented that indicates some mtbi patients have motivation to perform poorly on measures of neuropsychological functioning. However, several factors related to these assumptions merit further investigation. First, no consensus exists as to what exactly is being measured, as the neuropsychological community has yet to operationally define the construct of interest (i.e., tests say they are measuring effort but published results are identifying the behavior as malingering). As noted, malingering is difficult to prove, rarely diagnosed, and most likely not representative of the phenomenon of interest. Thus, for the purposes of this investigation, Sweet et al s (2000) definition of insufficient effort was utilized when referring to behavior. Specifically, insufficient effort includes the degree of effort that reaches a meaningful clinical threshold of being incomplete or partial and is significantly worse than performance standards known to reflect genuine neurological disorder (p.107). Second, methodological issues in the research literature may artificially contribute to the misclassification of mtbi patients with true, chronic cognitive deficits as individuals exhibiting poor effort. Poor documentation of time since injury, the use of prospective versus clinical studies, data pooling to describe severity of deficits, and low sensitivity of neurocognitive tests may contribute to confusion regarding true 24

33 neurocognitive variables underlying mtbi, thus affecting effort performance. The current study addressed these issues in an attempt to better understand how these methodological factors may influence the classification of some mtbi patients as exhibiting poor effort. Third, there are very few studies that have directly compared neurocognitive variables between groups consistently shown to fail tests of effort at higher rates. Although two studies have shown mtbi patients failing effort tests also perform below expected levels on neuropsychological tests, neither study addressed specific test performance in relation to measures of effort. The present study compared neurocognitive variables within and between groups to a test of effort to discern whether any underlying variables contribute to group performance. Fourth, although a few studies have shown that mtbi patients perform more poorly on tests of effort and neurocognitive ability than more severe TBI patients, no found studies have directly compared mtbi effort and cognitive performance to dementia patient performance. This is despite the fact that evidence has shown the two groups have similar neurocognitive deficit profiles, as well as similar effort test performance. The current analysis compared performance between these groups on the specified measures of interest. Finally, evidence has been presented to illustrate a simulator pattern on effort tests; however, current research does not currently support a simulator pattern in neurocognitive test performance. The present investigation examined test performance 25

34 between groups (analog simulators vs. mtbi) to identify whether or not such a pattern does exist. Thus, the overall purpose of the present study is to determine the underlying construct of the MSVT that accounts for effort in mtbi patients by comparing and contrasting mtbi with dementia and an analog simulation. Hypotheses First, it is hypothesized that mtbi will not differ from dementia patients in the set of neurocognitive variables that predict MSVT performance. Second, it is hypothesized that mtbi will differ from analog simulators in the set of neurocognitive variables that predict MSVT performance. Third, it is hypothesized that mtbi will not differ from dementia patients in failed MSVT subtests. Fourth, it is hypothesized that mtbi will not differ from dementia in impaired neurocognitive function as measured by standardized neuropsychological tests. Fifth, it is hypothesized that mtbi will not differ from analog simulators in failed MSVT subtests. Finally, it is hypothesized that mtbi will differ from analog simulators in impaired neurocognitive function as measured by standardized neuropsychological tests. 26

35 CHAPTER II METHODS Participants Participants for the current study were recruited from a University based medical facility in Ft. Worth, Texas as well as a private practice facility in Dallas, Texas, as they presented for a standard neuropsychological evaluation as part of their primary diagnosis or continued care. Participants involved in the mtbi group were those individuals with loss of consciousness <30 minutes, or that received a Glasgow Coma Scale score of 13-15, with no skull fracture on physical exam or nonfocal neurologic exam and/ or an objectively documented incident with subsequent symptoms. Participants involved in the dementia group were at least 55 years old and presented for outpatient neuropsychological evaluation of dementia. Additionally, all participants identified English as their primary language and demonstrated adequate literacy and visual acuity. These requirements were screened for during the recruitment process by verbal questionnaire. Physician approval of medical stability was obtained for both participant groups. Participants in the analog simulator group were recruited from a group of graduate and undergraduate students taking classes in the Department of Rehabilitation, Social Work and Addiction at the University of North Texas. Participants in the analog group were at least 18 years of age and enrolled as graduate or undergraduate students at the University of North Texas, Denton campus. As part of 27