Rates of apparently abnormal MMPI-2 profiles in the normal population

Area of Science:

• Psychological assessment
• Psychometrics
• Clinical psychology

Background:

• The Minnesota Multiphasic Personality Inventory-2 (MMPI-2) is a widely used psychological test.
• Interpreting multiple MMPI-2 scales may lead to an increased rate of false positives in identifying psychopathology.
• Understanding the base rate of chance scores in a normal population is crucial for accurate interpretation.

Purpose of the Study:

• To estimate the base rate of apparently abnormal MMPI-2 scores in a normal population when multiple scales are interpreted.
• To determine the likelihood of obtaining clinically significant scores by chance across different MMPI-2 scale groupings.

Main Methods:

• Monte Carlo simulations were used to re-sample MMPI-2 standardization data.
• The study focused on estimating the chance occurrence of scores considered clinically significant (65T) on various MMPI-2 scales.

Main Results:

• Approximately 36.8% of normal adults obtained at least one clinically significant score on the MMPI-2 Clinical scales.
• Higher rates of chance scores were observed on Content (38.3%) and Supplementary (55.1%) scales.
• Interpreting numerous scales together revealed that 47.4% of normal individuals had at least three seemingly meaningful scores, and 30.1% had five or more.

Conclusions:

• The number of MMPI-2 scales that can be meaningfully interpreted in clinical practice is limited due to chance findings.
• High T-scores are necessary for confidence in MMPI-2 interpretations, even when focusing solely on Clinical scales.
• Clinicians should be cautious when interpreting multiple MMPI-2 scales to avoid overpathologizing normal individuals.