Psychiatric conditions are easy to fake, because there are no truly objective tests for their diagnoses. In one survey, members of the American Board of Clinical Neuropsychologists estimated that some degree of symptom exaggeration occurs in 39% of mild head injury cases, in 30% of disability assessments, and in 29% of personal injury cases (Mittenberg W et al., J Clin Exp Neuropsychology 2002;24:1094-1102). The diagnoses most commonly malingered are probably ADHD and PTSD. In both cases, diagnosis is based on a checklist of historical symptoms, and both diagnoses potentially yield a bounty of secondary gain-disability benefits for PTSD, and academic accommodations and stimulants in the case of ADHD.

The prevalence of malingered PTSD symptoms is hard to assess, but estimates have varied from 1% to 75%, depending on the clinical setting and the definition of malingering (Hall and Hall, J Forensic Sci 2007;52:717-725). The actual prevalence of ADHD malingering has never been formally studied, but the high rate of stimulant diversion on college campuses implies that the problem is significant.

In order to assess how easy it might be for college students to malinger ADHD, researchers in one study randomly assigned healthy college undergrads to two groups: “ADHD Fakers” and “Honest Normals.” They had both groups of students complete the Connors’ Adult ADHD Rating Scale, and they compared these scores with a historical database of genuine ADHD patients’ scores on the same test. The bottom line was that Fakers were extremely good at feigning ADHD symptoms, demonstrating an almost perfect ability to fake items on the Connor’s scale corresponding to DSM-IV symptoms. In general, fakers performed at a significantly more impaired level than patients with bona fide ADHD, but this difference was not dramatic enough for the researchers to accurately identify malingerers based on test scores alone (Harrison AG et al., Arch Clin Neuropsychology 2007;22:577-588).

Most neuropsychologists include so-called “symptom validity tests” in their test batteries, such as the “F scale” in the Minnesota Multiphasic Personality Inventory (MMPI). These scales are fairly accurate in detecting a pattern of false exaggeration of symptoms.

There are several other tests that are specific for detecting malingering, with names such as the Test of Memory Malingering, and the Validity Indicator Profile. The essence of such tests is that they try to make very easy questions appear to be difficult. Patients without severe and obvious memory impairments should do well on these tests; those who do poorly are suspected of faking pathology.

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An example of such a test that you easily perform in the office is the Rey Fifteen Item Memory Test (Spreen O and Strauss E, A Compendium of Neuropsychological Tests, 2nd Ed, Oxford U. Press 1998). Patients are shown the items in the figure on the center of this page for 10 seconds and then asked to reproduce these items from memory.

You have to emphasize that this is a “very difficult” test and that there are “fifteen different designs” to memorize. In reality, of course, the test includes repeating patterns that make it quite easy to reproduce. The test is useful for patients who seem cognitively normal during the evaluation interview but who nevertheless report specific cognitive symptoms. An apparently normal patient who cannot recall at least 9 of 15 items (that is, at least 3 of the 5 character sets) may well be malingering (though further evaluation for cognitive impairment may be warranted).

In order to detect malingering in PTSD, there are several clinical pearls that may be more useful than formal testing. Look for some or all the following: “textbook” description of symptoms (“I have intrusive memories”); vague descriptions that could fit any disorder ( “Well I have bad dreams…”); excessively dramatic presentations (for example, a convulsive startle reflex in response to a knock on your office door); consistent absence of response to any and all treatment strategies; and reluctance to allow you to talk to a third party to corroborate symptoms. None of these are pathognomonic of malingering, of course, but any of them might raise your suspicion

and prompt you to refer for more formal neuropsychological testing to clarify matters.