Psychol. Inj. and Law (2009) 2:284–293 DOI 10.1007/s12207-009-9057-0
Symptom Validity Testing in Claimants with Alleged Posttraumatic Stress Disorder: Comparing the Morel Emotional Numbing Test, the Structured Inventory of Malingered Symptomatology, and the Word Memory Test Thomas Merten & Elisabeth Thies & Katrin Schneider & Andreas Stevens
Received: 23 February 2009 / Accepted: 5 November 2009 / Published online: 5 December 2009 # Springer Science+Business Media, LLC 2009
Abstract In independent medical examinations, unjustified claims of posttraumatic stress disorder (PTSD) are to be expected at an increased rate. In a prospective study, consecutive cases of patients claiming PTSD who underwent independent neuropsychiatric evaluation were analyzed. For 61 adult patients, results of three symptom validity tests (Morel Emotional Numbing Test, Structured Inventory of Malingered Symptomatology, and Word Memory Test) were available. Seventy percent of all claimants showed probable negative response bias in at least one of the three tests, 25% in all three tests. High probability of negative response bias was associated with symptom overreporting and demonstration of cognitive deficits in performance tests. The results indicate that high rates of uncooperativeness must be expected in civil forensic patients with claimed PTSD. A multi-method approach to the assessment of response distortion in PTSD claimants is indicated. Keywords Posttraumatic stress disorder . Malingering . Symptom validity testing . Negative response bias . Morel Emotional Numbing Test . Symptom overreporting
T. Merten (*) Vivantes Netzwerk für Gesundheit, Klinikum im Friedrichshain, Klinik für Neurologie, Landsberger Allee 49, 10249 Berlin, Germany e-mail:
[email protected] E. Thies : K. Schneider : A. Stevens Medizinisches Gutachteninstitut Tuebingen, Tuebingen, Germany
Introduction In independent medical examinations, unjustified claims of posttraumatic stress disorder (PTSD) are to be expected at an increased rate. Claims of PTSD in forensic examinations or in other contexts where primary or secondary gain is at stake should not be taken at face value (Freeman et al. 2008; McNally 2003; Rosen 2004; Taylor et al. 2007; for a recent review of the relevant literature, see Rubenzer 2009). Reports about the aftermath of the sinking of the Aleutian Enterprise on 22 March 1990 (Rosen 1995), the implausibly high rate of chronic PTSD in survivors of the HMAS Voyager accident in 1964 (Rosen 2004), and the high number of PTSD claims by Vietnam war veterans who had not had combat exposure or had not even served in Vietnam or in the military at all (e.g., McNally 2007) show that false claims not only occur at an elevated rate but are also likely to be uncritically accepted by clinical and forensic professionals. Similarly, a sizeable proportion of criminal offenders may claim symptoms of posttraumatic stress to avoid prosecution (Resnick and Harris 2002). Moreover, Rosen's (1995) report has drawn attention to another problem, that of symptom coaching. After the sinking of the Aleutian Enterprise, survivors were specifically coached by their attorneys to malinger PTSD. Symptom lists were used to learn and feign the typical symptoms so convincingly that, ironically, the presented symptomatology was regarded as evidence substantiating the authenticity of the alleged trauma. PTSD has been shown to be feigned easily, in particular, when the diagnosis is mainly based on symptom reports, either spontaneous or obtained with self-report questionnaires
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like the Impact of Event Scale—Revised (IES-R; Weiss and Marmar 1996). Most of the PTSD scales currently available do not contain subscales assessing symptom exaggeration or unspecific or inconsistent symptom endorsement. Even in the absence of coaching, the symptoms of PTSD may be easily learned because descriptions are accessible through the media and also because patients are routinely instructed about the symptoms of PTSD by psychotherapists. Available base rate estimates suggest that feigned PTSD is not infrequent in forensic neuropsychological contexts. Lees-Haley (1997) analyzed a sample of 492 trauma victims who were involved in personal litigation. Using various MMPI-2 validity scales, possible malingering was found in 20% to 30% of the cases. Frueh et al. (2000) reported apparent symptom overreporting in combat veterans evaluated for PTSD in at least 20% of cases. Freeman et al. (2005) assessed 33 Vietnam veterans and found clear evidence of symptom exaggeration in 55% using the Structured Interview of Reported Symptoms (SIRS; Rogers et al. 1992). Greiffenstein et al. (2004) found the MMPI-2 validity scales of the F family to be not particularly sensitive to identifying improbable symptom endorsement in the context of claimed posttraumatic stress. However, the Fake Bad Scale of LeesHaley et al. (1991) performed much better. With a cut score of above 30, the specificity of the scales for identifying symptom magnification reached 100% for both males and females. In contrast, a number of studies (Arbisi et al. 2006; Bury and Bagby 2002; Efendov et al. 2008; Elhai et al. 2000, 2001) as well as a meta-analysis (Rogers et al. 2003) found the scales of the F family to demonstrate superior performance in identifying feigned PTSD in the context of psychiatric setting (cf. also Resnick et al. 2008). While some of the literature suggested relative independence of exaggerated PTSD symptoms and failure in cognitive symptom validity tests (Demakis et al. 2008), another study reported that a relatively high proportion of claimants with purported symptoms of posttraumatic stress demonstrated insufficient cognitive test effort (Stevens et al. 2008). The latter authors analyzed test results of 233 claimants who underwent independent neuropsychiatric evaluation. Among those 63 patients who reported cognitive impairment as well as symptoms of PTSD, 28 (44%) failed in a cognitive symptom validity test. Demakis et al. (2008) found a failure rate of 29% in at least one cognitive symptom validity measure and 48% in at least one psychological validity indicator. Greiffenstein and Baker (2008) have more recently drawn attention to one problem of particular salience: those patients who claimed psychological stress and mild traumatic brain injury (mTBI) at the same time were more likely to produce invalid test results and symptom overendorsement. The authors concluded that “[a]lthough rare cases of dual diagnosis cannot be ruled out, our findings strongly suggest late-appearing mTBI-PTSD
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claims are so intertwined with secondary gain that this dual diagnosis may only be a byproduct of it” (p. 565). The liability of PTSD to malingering has also been recognized by the authors of DSM-IV (American Psychiatric Association 1994) in a cautionary note. It reads: “Malingering should be ruled out in those situations in which financial remuneration, benefit eligibility, and forensic determinations play a role” (p. 467). However, DSM-IV does not provide guidelines on how to do this. “Ruling out” may not be possible in the literal sense of the notion (for a more detailed discussion on this topic, cf. Rosen 2006; Rosen and Taylor 2007). Consequently, Spitzer et al. (2007) have included Exclusion of Malingering as criterion G in the suggested diagnostic criteria for DSM-V PTSD. Neuropsychology has always been conceptually linked with PTSD. The DSM-IV (American Psychiatric Association 1994) symptom spectrum comprises a number of neuropsychologically relevant issues related to consciousness (dissociative episodes), memory (intrusive recollections, inability to recall an important aspect of the trauma), attention (hypervigilance, difficulty concentration, and exaggerated startle response), and other cognitive phenomena (sense of reliving the experience, illusions, and hallucinations). Moreover, complaints about cognitive dysfunctions are often part of a patient's symptom report, with particular emphasis on impaired memory and concentration. While a number of studies have reported cognitive impairment in PTSD patients (e.g., Beers and De Bellis 2002; Larbig et al. 2008; Vasterling et al. 2002), the question of the nature and the origin of cognitive symptoms is highly controversial. Thus, Gilbertson et al. (2006) found in a study of veterans with pairs of twins (one of which was combat-exposed while the other was not) that specific domains of cognitive impairment may be conceived of as premorbid risk factors in PTSD rather than be caused by posttraumatic stress. Thus, neuropsychological factors may be linked to psychiatric vulnerability and resilience. In a review on neurocognitive functioning in PTSD, Horner and Hamner (2002) came to the conclusion that the extent to which observed deficits in traumatized individuals were attributable to PTSD remained unclear. They identified a number of potential confounding variables, in particular medical diseases, psychiatric comorbidity, preexisting attention-deficit/hyperactivity disorder, and substance abuse. Also, motivational factors have rarely been discussed in the literature despite evidence of symptom exaggeration and suboptimal performance in a subsample of patients. The authors concluded that “these factors could be of greatest salience among patients currently undergoing treatment for PTSD” (p. 27). In a more recent critical review, Moore (2008) arrived at the same conclusion. She wrote: “Preexisting negative appraisals, impaired retrieval of autobiographical memories, and decrements in verbal
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memory may represent trait-like cognitive phenomena that denote greater vulnerability to PTSD following trauma and predict symptom course” (p. 22). Claims of cognitive impairment are also frequent at the level of the individual, particularly in patients who are evaluated in forensic contexts. Under such circumstances, neuropsychological examinations may be warranted in order to assess a patient's functional level and possible functional impairment. On the background of possible negative response bias in patients with claimed trauma symptoms, neither symptom report nor poor performance on cognitive measures of attention, memory, and executive functions should be taken at face value without further evaluation. In forensic neuropsychology, a number of approaches and special instruments have been developed to tackle the problem of malingered neurocognitive symptoms. Instruments like the Test of Memory Malingering (Tombaugh 1996), the Amsterdam Short-Term Memory Test (Schmand and Lindeboom 2005), or the Word Memory Test (WMT; Green 2003) may be useful for detecting malingered claims of mental disorders if cognitive impairment (such as attention or memory deficits) is part of the spectrum of alleged symptoms. This was convincingly demonstrated in a PTSD case study by Rosen and Powel (2003) in which a 40-year-old claimant produced a below-chance response pattern in a forced choice symptom validity test (SVT) showing that with a very high degree of certainty, he knew the correct answers but deliberately chose the incorrect ones. In the Demakis et al. (2008) study, it was shown that claimants who failed cognitive SVTs were indeed more likely to produce poorer results in neuropsychological tests proper. In contrast to the cognitive SVTs discussed above, the Morel Emotional Numbing Test (MENT; Morel 1998a, b) was specifically designed to identify feigned PTSD. It focuses on “emotional numbing” among the PTSD symptoms. Contrary to what persons who present non-authentic symptoms may think, the MENT is successfully solved by virtually any adult, with the exception of patients suffering from severe neurocognitive disorders related to word processing, visual acuity, spatial neglect, or face processing. However, claimants who try to convince the examiner of the presence of PTSD symptoms may distort their performance and score implausibly low—below a cutoff indicating negative response bias. The MENT has demonstrated its usefulness in a number of studies which have recently been summarized by Morel and Shepherd (2008). They estimated the sensitivity (percentage of malingerers detected) of the MENT over five published studies to be between 63% and 92%, with a pooled sensitivity estimate of 79%. Specificity estimates (percentage of non-malingerers correctly classified as credible examinees) ranged from 77% to 100%, with a pooled estimate of 96%. Moreover, Morel and Marshman
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(2008) have reformulated Hartman's (2002) criteria for evaluating symptom validity tests. Two major test modifications have been described. First, Messer and Fremouw (2007) developed a revision (MENT-R) using different pictures of facial affect expressions, while a Dutch version of the test was used by Geraerts et al. (2006), again with different photographs. For both versions, promising results have been obtained. For the current study, an authorized German version of the original test material was produced (Morel 2007). The current study presents results obtained with a German sample of disability claimants who underwent independent psychiatric assessment and basic psychological testing. Besides the MENT, results from two well-established symptom validity measures and validity indicators derived from a standard psychological test were available. While the WMT is a forced-choice SVT, which is in widespread use among neuropsychologists in many different countries, the Structured Inventory of Malingered Symptomatology (SIMS; Smith and Burger 1997; Widows and Smith 2005) is a selfreport questionnaire especially designed for the detection of negative response bias. All three SVTs, the MENT, the WMT, and the SIMS, resort to different approaches for assessing response validity. Until now, data for comparing MENT results with other instruments have been scarce. In a recent study by Morel (2008), the classification rates of the MENT and the WMT were tested with a sample of 37 veterans. The author found a very high correlation of −0.83 between the MENT and the WMT Delayed Recognition scores and good agreement with classification results. Previously reported prevalence rates of negative response bias in PTSD claimants led to hypothesis I, stating that a sizable minority (about 50%) of civil forensic patients show evidence of negative response bias when the decision is based on at least one of several indicators for negative response bias. Previous research on intercorrelations between pairs of different cognitive SVTs and between cognitive and psychological validity measures (e.g., Inman and Berry 2002; Merten et al. 2007a; Nelson et al. 2003; Ruocco et al. 2008) suggested also that there might be small to moderate associations between pairs of symptom validity measures (hypothesis II), according to the guidelines proposed by Cohen (1988). If both hypotheses are corroborated by the data, this would, in the authors' opinion, support a multi-method approach to symptom validity assessment in claimants with alleged PTSD.
Method Research Participants From October 2007 to October 2008, a total of 77 claimants underwent independent psychiatric examination for alleged
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PTSD. The comprehensive examination included a thorough medical, neurological, and psychiatric evaluation. All claimants were also referred to a psychological evaluation in order to determine the nature and extent of possible cognitive impairment and to rule out malingering. The psychological evaluation included self-report questionnaires, performance tests, and SVTs. The total sample consisted of 33 men and 44 women at ages ranging from 22 to 68 years (M=42.8, SD=11.1). For an estimate of educational backgrounds, the International Standard Classification of Education or ISCED1997 (United Nations Educational, Scientific and Cultural Organization 1997) was used in its specification for Germany (Schroedter et al. 2006). Six participants had “primary education or first stage of basic education”, 11 “lower secondary or second stage of basic education”, 44 “(upper) secondary education”, seven “post-secondary non-tertiary education”, and nine had completed the “first stage of tertiary education.” Nearly half of the participants had experienced a road accident (n=35, 45.5%), 28 (36.4%) were involved in an industrial accident, seven (9.1%) had been assaulted and robbed, three (3.9%) had witnessed the death or a serious disease of another person, two (2.6%) were victims of other kinds of violence, one (1.3%) had witnessed violence against another person, and one (1.3%) claimed PTSD resulting from medical malpractice. In total, 16 patients from the sample (20.8%) maintained that they could not fully remember the course of the traumatic event. Eleven patients (14.3%) claimed to have sustained mild traumatic brain injury, eight of which (10.4%) reported a loss of consciousness. There were no cases of moderate or severe brain injury among the claimants.
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Of all the claimants, 62.3% showed one or more atypical features which made their complaints implausible and the diagnosis of PTSD, which they had been previously given, improbable. The detailed analysis presented in Table 1 is an adaptation of the procedure proposed by Greiffenstein et al. (2004). Patients were eligible for the following analyses if they were fluent speakers of German and if complete data sets were available for the MENT, the WMT, and the SIMS. This resulted in a sample of 61 patients (27 men and 34 women) with an age range from 22 to 68 years (M=43.3, SD=11.3). For an estimate of educational backgrounds, the International Standard Classification of Education or ISCED-1997 (United Nations Educational, Scientific and Cultural Organization 1997) was used in its specification for Germany (Schroedter et al. 2006). Three participants had “primary education or first stage of basic education”, eight “lower secondary or second stage of basic education”, 38 “(upper) secondary education”, four “post-secondary non-tertiary education”, and eight had completed the “first stage of tertiary education.” Post hoc analyses showed no significant differences between the total sample and the subsample of n=61 in terms of age, gender, education, and number of implausible PTSD features as listed in Table 1. Participants were mainly excluded from the final analyses because they were not native speakers of German, which resulted in incomplete data sets and test data which were not directly comparable to those obtained from native German speakers. All participants signed an informed consent allowing the storage and scientific analysis of the data. There was no sample overlap with the Stevens et al. (2008) study mentioned in “Introduction.”
Table 1 Description of implausible features of the patients who underwent psychiatric examination for alleged PTSD for both the total sample (N=77) and the subsample selected for further analysis (n=61) Implausible features
Event does not fulfill DSM-IV A1 criterion Delayed symptom onset of more than 1 month Amnesia for event and all the same claims of re-experiencing event 3 or more comorbid psychiatric diagnoses recorded Multiple diffuse complaints not matching any known disease patterns Number of implausible features found per patient None 1 or more 2 or more 3
Total sample (N=77)
Selected sample (n=61)
n
%
n
%
17 19 8 8 16
22.1 24.7 10.4 10.4 20.8
14 15 6 8 13
23.0 24.6 9.8 11.1 21.3
29 48 15 5
37.7 62.3 19.5 6.5
24 37 14 5
39.3 60.7 23.0 8.2
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Procedure and Instruments Results of three symptom validity tests and a further symptom validity measure derived from a standard test were available. These were: 1. The German adaptation of the MENT (Morel 1998a), which, as outlined above, is a test specifically designed for detecting feigned PTSD. 2. The SIMS (Widows and Smith 2005), which is a 75-item questionnaire developed to assess a patient’s endorsement of unlikely, bizarre, or very rare symptoms. Patients who show negative response bias may believe that they belong to known syndromes. A total score and scores for five symptom domains are obtained: Low Intelligence, Affective Disorders, Neurological Impairment, Psychosis, and Amnestic Disorders. The German version was developed by Cima et al. (2003) and appears to be carefully validated using a total sample of more than 300 research participants. The authors also checked the cutoff for the diagnosis of negative response bias and proposed a cut score of 16. In a separate study, Merten et al. (2007b) analyzed the practical value of the German SIMS with a sample of civil forensic patients. 3. The computerized version of the WMT (Green 2003). This is a symptom validity test which apparently measures memory, but, in fact, the memory demands of the first subtests are relatively low so they reflect test motivation (or effort) rather than cognitive impairment. The German WMT was developed by Brockhaus and Merten (2004) and was included in a number of studies which demonstrated the equivalence of the original and the German versions of the test. Thus, the German WMT is an integral part of the multilingual computer program (Green 2003). Published results obtained with the German version are usually discussed alongside those obtained with the original WMT (e.g., Green 2007). For the present analyses, the core symptom validity indicators are considered: Immediate Recognition trial, Delayed Recognition trial, and Consistency. For the classification fail vs. pass, the original, more conservative cutoffs proposed by the author (Green 2003) were used. For the correlational analysis, mean scores from the three symptom validity indicators were computed. 4. From the WAIS-III subtest Digit Span (Wechsler 1997), the Reliable Digit Span (RDS) was computed according to the procedure described by Greiffenstein et al. (1994). RDS has repeatedly been used as a symptom validity measure, but classification results have usually been modest in comparison with special SVTs (e.g., Merten et al. 2007a).
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Furthermore, results of the following questionnaires and performance tests were analyzed: 5. The German version of the Impact of Event Scale— Revised (Maercker and Schützwohl 1998) is not directly comparable to the original questionnaire by Weiss and Marmar (1996) since it maintains the original IES response format scoring 0, 1, 3, and 5 points for the four responses “not at all”, “rarely”, “sometimes,” and “often”, respectively. A total score and scores from three symptom clusters (Intrusion, Hyperarousal, and Avoidance) are obtained. The scale scores obtained in this study were compared with mean scores reported by Maercker and Schützwohl (1998) for former political prisoners in East Germany (IES-R Intrusion=18.7, SD=10.3; Avoidance=13.8, SD=9.2; Hyperarousal=16.7, SD=11.2) and for crime victims (IES-R Intrusion=16.4, SD =10.4; Avoidance=15.4, SD=8.6; Hyperarousal=14.7, SD=14.7). 6. The WAIS-III subtest digit span (Wechsler 1997) is a measure of verbal short-term memory and working memory. From the results, the RDS was computed as outlined above. 7. The Trail Making Test (Reitan 1992) is a test of attention and executive functions which is commonly used in neuropsychological assessment. 8. Visual memory was tested with the subtest Visual Memory, from the Visual and Verbal Memory Test (Schellig and Schächtele 2001). The assumption of no false positives in all SVTs cannot be made with full confidence (cf. Merten et al. 2007a). In order to check the effects of malingering on self-report and performance tests, a known-group design was employed using two extreme groups: those passing all three SVT and those failing all three. This design is based on the following underlying assumptions. Any of the three SVTs may produce false positive classifications. However, failing in all three SVTs indicates negative response bias with high probability. In contrast, passing all three SVTs does not exclude negative response bias, but the probability of it may be judged to be minor. So, comparing those participants who pass all three SVTs with those who fail all three may give a rather robust reflection of the effects of negative response bias. It should be kept in mind that normal ranges in SVTs are defined differently than in standard psychological tests. Rather than assuming an a priori probability of 5% for any trial to fall outside the normal range, the cutoff values in SVTs are set high to yield very low estimates of false positives, e.g., p(false positives)
