Beyond Rare-Symptoms Endorsement: a Clinical Comparison Simulation Study Using the Minnesota Multiphasic Personality Inventory-2 (MMPI-2) with the Inventory of Problems-29 (IOP-29)

Abstract

To date, the MMPI-based, rare-symptom detection strategy is considered one of the most effective ones in symptom validity assessment. Because many of the items of the Inventory of Problems-29 (IOP-29) were designed specifically to provide incremental validity over the MMPI F scales, this study tested whether using the IOP-29 in combination with the MMPI-2 would provide higher classification accuracy compared to using either instrument alone. A total of 155 Italian adult individuals contributed to this study. About half (n = 93) were experimental malingerers (expMAL) instructed to simulate depression without being detected as feigners. The others were either (a) depressed patients in treatment (n = 36) or (b) individuals evaluated for possible malingering associated with work-related stress and considered to be genuinely affected by depression (n = 26). All were administered the Italian versions of both the MMPI-2 and the IOP-29. As expected, both instruments were highly effective in discriminating feigned from bona fide depression, with AUC values ranging from .77 to .90. More importantly, when entering the IOP-29 after each of the MMPI-2 scales under consideration (i.e., F, Fb, and Fp), the logistic regression models predicting group membership (0 = patient; 1 = expMAL) improved significantly. Likewise, each of the three MMPI-2 scales under consideration also significantly improved the prediction of group membership, when entered after the IOP-29. These findings thus indicate that using the MMPI-2 together with the IOP-29 could provide incremental validity over using either instrument alone, when testing depression-related complaints.

Appendices

Appendix 1. Instructions for Experimental Malingerers (ExpMAL)

Instructions and Vignette to Feign Depression

In this study, you will be asked to complete a series of tests that may measure a variety of changes that people experience following a diagnosis of Major Depression Disorder. When you are answering the questions on the tests, I would like you to put yourself in the shoes of a person who has had an accident at work and is now suffering from mental health problems—namely, depression—related to that accident and for which he has requested to be put on disability. That is, try to answer the questions of these tests like you think that a person that really suffers from depression might do. To help you provide a credible presentation, please read the following text, and try to pretend that you are the person depicted in this scenario.

“You are an administrator at a small, well-established firm. Your boss has been trying to cut expenses by having the cleaning crew work before regular work hours are over, thus getting the job done at a cut rate. You have repeatedly informed him that this is not a safe working condition for the employees, but he has not changed the procedure. One day, near the end of the day, you are leaving to do a special errand for your boss. As you cross a freshly mopped floor, you slip and fall, landing hard on your tailbone. As a result, you have been out of work for 2 weeks on disability and continue to experience a fair amount of pain, particularly when you sit for any length of time. The workers compensation physician insists that he can find nothing to explain the pain and refuses to authorize any more time off or disability payments, stating that you are able to return to work, a job that requires long periods of time sitting at your computer. You are angry with your boss for the injury you have and frustrated at the physician’s apparent collusion with your boss to unreasonably limit your recovery time (thereby cutting off his disability payments). Before terminating your case, the physician refers you to the staff psychologist for a routine evaluation. You correctly realize that this evaluation is your only opportunity to remain on disability under your employer’s obligation. You have no additional coverage and need an income until you are fully recovered. You also feel that your boss is responsible, and that money should come from the company through workers compensation. You know well that workers compensation will continue providing benefits to patients who are psychologically disturbed as a result of a work-related accident. This would not be too unusual because you have tried to take measures to avoid the problem, and now are suffering as a result of your boss’s negligence. So, your only choice is to present yourself as having significant depression on the tests that the psychologist is going to give you. You therefore decide to attempt to present yourself as having a major depression as the result of your accident, to remain on disability.”

Description of Symptoms of Depression and Cautionary Statement

Now, please take a look at the symptoms that characterize a Major Depression Disorder. Keep in mind that depressed patients typically have 5 or more of the following symptoms, but most likely not all of them.

• 1. Depressed mood most of the day, nearly every day (e.g., feeling sad, empty, hopeless)

• 2. Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day

• 3. Significant weight loss when not dieting or weight gain, or decrease or increase in appetite nearly every day

• 4. Insomnia or hypersomnia nearly every day

• 5. Psychomotor agitation or retardation nearly every day

• 6. Fatigue or loss of energy nearly every day

• 7. Feelings of worthlessness or excessive or inappropriate guilt nearly every day

• 8. Diminished ability to think or concentrate, or indecisiveness, nearly every day

• 9. Recurrent thoughts of death, recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide.

When you take the tests and try to pretend you suffer from a Major Depressive Disorder, please keep in mind that if you present your condition in an extremely dramatic way, your performance may not be believable, and the examiner might understand that you do not suffer from depression but are only faking it. So, try to not “over-do it”.

If you will be able to produce test results that are consistent with those produced by people who really suffer from Major Depression Disorder and you will not look like a feigner, you may win a small prize consisting of a 20€ gift card!

Appendix 2. Formula Used to Calculate the Z Average of MMPI-2 F and IOP-29 FDS

$$ Z\ \mathrm{average}=\frac{\left(\frac{\mathrm{MMPI}2\ \mathrm{F}\ \mathrm{raw}-9.0}{5.1}\right)+\left(\frac{\mathrm{IOP}29\ \mathrm{F}\mathrm{DS}-.27}{.22}\right)}{2} $$

Note: For each scale, Z values were calculated using the patients’ data only, so to avoid possible outliers or extreme variability.