A study of the Minnesota Multiphasic Personality Inventory-2 (MMPL-2) found that the validity scales and indicators were better at detecting feigned schizophrenia than feigned depression (J Personality Assessment, 1997, 68(3), 650-664).

The researchers compared 40 nonclinical persons faking either schizophrenia or depression with 40 patients diagnosed with each of these psychiatric disorders. The profiles of both malingerers and patients were also compared with 40 honestly responding nonclinical participants. Diagnoses of depression and schizophrenia were made independent of MMPI-2 test results. Research participants were provided with a description of the disorder and then asked to answer MMPI-2 items as if they were suffering from that particular disorder.

MMPI-2 validity scales, F(b) (malingering) and F(p) (psychopathology), and clinical scale profiles for honest-response and feigned-response nonclinical participants, patients with major depression, and patients with schizophrenia were given a Mean T Score (Clinical scales included, for example, masculinity-femininity, hypomania, and social introversion). The patient samples scored near or above a T of 65 on most of the clinical scales. The honestly responding nonclinical participants, in contrast, scored near or below a T of 50 on all 10 clinical scales. The patients with depression scored significantly higher on the depression scale than did the honestly-responding nonclinical participants. The validity scales, malingering and psychopathology best distinguished patients with schizophrenia from subjects feigning it. The malingering measure best differentiated between actual and malingered major depression.

Overall, MMPI-2 validity scales and indicators were more effective in detecting faked schizophrenia, suggesting that it is more difficult to detect malingered depression than feigned schizophrenia. Perhaps this is because symptoms associated with schizophrenia are more varied but not universally experienced by schizophrenics. Individuals feigning schizophrenia may therefore be more likely to endorse symptoms associated with, but infrequently experienced by, patients with schizophrenia, such as visual hallucinations. The symptoms associated with major depression, on the other hand, are more universally experienced by patients with that disorder.

Major depression is one of the most common mental disorders and many disability claims are based on its alleged presence. Schizophrenia is often malingered in criminal competency and responsibility assessments.

The MMPI-2 is often given to validate psychopathology, so research into determining malingering of specific disorders is very beneficial to forensic mental health professionals who perform civil and criminal evaluations.