Transcript Detecting Cognitive Malingering: State of the Art David Stigge-Kaufman Forensic Neuropsychology

Detecting Cognitive Malingering:
State of the Art
David Stigge-Kaufman
Forensic Neuropsychology
July 13, 2006
Malingering
• Definition
– Intentional production of false or greatly exaggerated symptoms
for the purpose of attaining some identifiable external reward
(Iverson & Binder, 2000)
• Often viewed as pejorative and controversial
– “In contrast to making the diagnosis of malingering, clinicians
seem to be much more comfortable diagnosing people with brain
damage, schizophrenia, alcohol or drug abuse, or personality
disorders.” (p. 831)
• Diagnostic Considerations
– V65.2 (DSM-IV-TR)
• “Additional condition that may be a focus of clinical attention”
– Differential diagnosis:
• Factitious Disorder, Somatoform Disorders, Depression
Malingering Checklist
A. Presence of a substantial external incentive
B. Evidence from neuropsychological testing
1.
2.
3.
4.
5.
6.
Definite negative response bias (below chance on a forced-choice measure of
cognitive function)
Probable response bias on a validity test
Discrepancies between test data and known patterns of brain functioning
Discrepancies between test data and observed behavior
Discrepancy between test data and reliable collateral reports
Discrepancy between test data and documented background history
C. Evidence from self-report
1.
2.
3.
4.
5.
Self-reported history discrepancy with documented history
Self-reported symptom discrepancy with known patterns of brain functioning
Self-reported symptom discrepancy with behavioral observations
Self-reported symptom discrepancy with reports from close informants
Evidence of exaggerated or fabricated psychological dysfunction
D. Behaviors meeting criteria from groups B and C not fully accounted for
by psychiatric, neurologic, or developmental factors
Slick et al., 1999; Lezak et al., 2004
Malingered Neurocognitive
Dysfunction (MND)
• Definite MND
• Probable MND
– Presence of a substantial
external incentive
– Presence of a substantial
external incentive
– Definite negative
response bias
– > 2 types of NΨ evidence*,
or, 1 type of NΨ evidence
plus 1 type of evidence
from self-report
– Negative response bias
cannot be otherwise
accounted for.
Slick et al., 1999
– Behaviors cannot be
otherwise accounted for
* not including negative response bias
Clinical Application
Case Example:
A middle aged electrician had passed out at work
due to a heat stroke. He was evaluated to
determine if the residual memory difficulty was
sufficiently severe to preclude his return to work.
Across all three delay sets for easy items of the
Victoria Symptom Validity Test, this man had
24/24 recognition. In contrast, he gave only three
correct responses on the 24 “hard” items.
Example
“Easy” Trial
“Hard” Trial
53921
46780 vs. 53921
54821 vs. 53921
Lezak et al., 2004, p. 776
Clinical Application
Case Example:
Because 24/24 easy items were correct but only 3/24 hard
items were correct, this did not suggest a random response
pattern. Normal, above chance performance on the easy
items demonstrated the patient’s understanding of the
instruction and that he was not confused about how to
respond. The below chance performances for the three hard
conditions have corresponding statistical probabilities of
.14, .004, and .004. Thus, when treated as independent
samples, the probability of occurrence is .0000022 (.14 X
.004 X .004). This success/failure pattern cannot be
explained away as due to confusion or misunderstood
instructions.
Lezak et al., 2004, p. 776
Effort, Motivation, & Response Styles
Frederick et al., 2000
Researching Malingering
• Case Studies
– Examine test data from individual cases, looking for performance
levels below chance on forced-choice tests.
• Simulation Studies
– May involve comparisons of 4 groups:
1) Normals faking impairment
2) Patients responding honestly
3) Normals responding honestly
4) Patients faking impairment
• Known-Group Designs
– Establish criterion groups (e.g., patients, malingerers), and conduct a
systematic analysis of similarities and differences between groups
• Differential Prevalence Designs
– Compare groups known to be higher in malingering to those who are
not
Sample Malingering Test
• What about the roles of perceived difficulty, face
validity, or test modality?
Test Popularity Among Experts
• Forced-choice testing:
• Forced-choice testing:
– Digit Recognition
– Visual Recognition
• Digit Memory Test (DMT)
• Portland Digit Recognition
Test (PDRT)
• Victoria Symptom Validity
Test (VSVT)
• Computerized Assessment
of Response Bias (CARB)
– Word Recognition
• 21-Item Test
• Word Memory Test
(WMT)
– Verbal & Nonverbal
Abilities
• Validity Indicator Profile
(VIP)
Slick et al., 2004
• Test of Memory
Malingering (TOMM)
• Letter Memory Test
• 48-Pictures Test
• Simplistic tests:
– Rey 15-Item Test
– Dot counting Test
– The b Test
Always/Often Used: > 40%
Always/Often Used: 30-39%
Always/Often Used: 20-29%
Always/Often Used: 10-19%
Test Sensitivity*
• Forced-choice testing:
• Forced-choice testing:
– Digit Recognition
– Visual Recognition
• Digit Memory Test (DMT)
• Portland Digit Recognition
Test (PDRT)
• Victoria Symptom Validity
Test (VSVT)
• Computerized Assessment
of Response Bias (CARB)
– Word Recognition
• 21-Item Test
• Word Memory Test
(WMT)
– Verbal & Nonverbal
Abilities
• Validity Indicator Profile
(VIP)
* Sensitivity = % of malingerers correctly classified
• Test of Memory
Malingering (TOMM)
• Letter Memory Test
• 48-Pictures Test
• Simplistic tests:
– Rey 15-Item Test
– Dot counting Test
– The b Test
Sensitivity: > 85%
Sensitivity: 70 – 84 %
Sensitivity: 50 – 69 %
Sensitivity: < 49 %
Lezak et al., 2004, Vickery et al., 2001
Test Specificity*
• Forced-choice testing:
• Forced-choice testing:
– Digit Recognition
– Visual Recognition
• Digit Memory Test (DMT)
• Portland Digit Recognition
Test (PDRT)
• Victoria Symptom Validity
Test (VSVT)
• Computerized Assessment
of Response Bias (CARB)
– Word Recognition
• 21-Item Test
• Word Memory Test
(WMT)
– Verbal & Nonverbal
Abilities
• Validity Indicator Profile
(VIP)
* Specificity = % of non-malingerers correctly classified
• Test of Memory
Malingering (TOMM)
• Letter Memory Test
• 48-Pictures Test
• Simplistic tests:
– Rey 15-Item Test
– Dot counting Test
– The b Test
Specificity: > 85%
Specificity: 70 – 84 %
Specificity: 50 – 69 %
Specificity: < 49 %
Lezak et al., 2004, Vickery et al., 2001
Malingering Patterns in NΨ Tests
• Pattern Analysis
– WMS-R
• Malingerers: Attention/Concentration < General Memory
• Opposite pattern to typical head injury
– WAIS-R: Digit Span
• Malingerers: Low digit span performance (ss < 4)
• Reliable Digit Span (sum of longest correct span for both trials < 7)
• Vocabulary – Digit Span (low digit span while vocabulary is high)
– CVLT
• Malingerers: Low recognition (hits & forced-choice)
• Cutoff scores for recall trials produce variable false-positive
rates
Iverson & Binder, 2000; Larrabee, 2005
Malingering Patterns in NΨ Tests
• Pattern Analysis
– Word Memory Test
• Malingerers: Inconsistent responding, poor initial recognition
• Pattern should reflect severity of impairments
– Category Test
• Malingerers: Poor performance on first 2 subtests
– Wisconsin Card Sorting Task
• Malingerers: Poor ratios of categories completed compared to
both perseverative errors and failure to maintain set
– Motor Functioning
• Malingerers: Suppress motor functioning to extreme levels
• Motor decline should only be associated with severe brain injury
Iverson & Binder, 2000; Larrabee, 2005
Symptom Exaggeration
• Self-Report of Symptoms
– May be exaggerated due to other variables (depression, pain, stress)
• e.g., Post-Concussive Syndrome persisting for more than 3 months
• MMPI-2
– Malingerers tend to show elevations in clinical scales 1, 2, 3, 7, and
8, the Fake Bad Scale (FBS), VRIN, TRIN, the InfrequencyPsychopathology Scale [F(p)].
– The F Scale and F – K does not appear to be as sensitive, and
therefore “valid” profiles may be obtained.
– Caution should be given to interpreting the clinical scales and F
Scale derivatives, as these can be easily influenced by psychiatric
comorbidities.
Iverson & Binder, 2000; Larrabee, 2005
Summary & Conclusions
• Defining Malingering
– External reward, negative response bias, and
discrepancies in NΨ data and/or self-report
• Combination of effort and motivation
– Case studies, simulation studies, known-group designs,
differential prevalence designs
• Detection of Malingering
– Numerous symptom validity tests
• Most forced-choice tests demonstrate excellent specificity, but
not all show high sensitivity
– Pattern analysis of NΨ data
– Symptom exaggeration
References
Frederick, R.I., Crosby, R.D., & Wynkoop, T.F. (2000). Performance curve
classification on invalid responding on the Validity Indicator Profile. Archives of
Clinical Neuropsychology, 15, 281-300.
Iverson, G.L., & Binder, L.M. (2000). Detecting exaggeration and malingering in
neuropsychological assessment. Journal of Head Trauma and Rehabilitation, 15,
829-858.
Larrabee, G.J. (2005). Forensic Neuropsychology: A Scientific Approach. New
York: Oxford University Press.
Lezak, M.D., Howieson, D.B., & Loring, D.W. (2004). Neuropsychological
Assessment (4th ed.). New York: Oxford University Press.
Slick, D.J., Sherman, E.M.S., & Iverson, G.L. (1999). Diagnostic criteria for
malingered neurocognitive dysfunction: Proposed standards for clinical practice
and research. The Clinical Neuropsychologist, 13, 545-561.
Slick, D.J., Tan, J.E., Strauss, E.H., & Hultsch, D.F. (2004). Detecting malingering:
a survey of experts’ practices. Archives of Clinical Neuropsychology, 19, 465473.
Vickery, C.D., Berry, D.T., Inman, T.H., Harris, M.J., & Orey, S.A. (2001).
Detection of inadequate effort on neuropsychological testing: a meta-analytic
review of selected procedures. Archives of Clinical Neuropsychology, 16, 45-73.