Construct Validity of the PHQ-9 Depression Screen: Correlations with Substantive Scales of the MMPI-2-RF
The PHQ-9 is a brief, 9-item, self-administered screening tool widely used in primary care medical settings to assess the potential presence of Major Depressive Disorder (MDD). Most published research on the PHQ-9 has focused on sensitivity and specificity with regard to the DSM-IV (American Psychiatric Association, in Diagnostic and statistical manual of mental disorders, 4th edn, American Psychiatric Publishing, Arlington, VA, 2000) categorical diagnosis of MDD, and, indeed, the PHQ-9 exhibits very good psychometric properties in this regard. The current research is an effort to more precisely assess what is being measured by the PHQ-9, given the notably heterogeneous nature of MDD as broad diagnostic category. Here, we provide correlations between the PHQ-9 and substantive scales of the Minnesota Multiphasic Personality Inventory-2-Restructured Form (MMPI-2-RF; Ben-Porath & Tellegen, in Minnesota Multiphasic Personality Inventory-Restructured Form: Manual for administration, scoring, and interpretation, University of Minnesota Press, Minneapolis, 2008/2011), a comprehensive measure of personality and psychopathology. Participants were 231 college student volunteers who completed the PHQ-9 and MMPI-2-RF as components of a broader research program. Results show that the PHQ-9 was strongly correlated with the broad Higher-Order EID-Emotional/Internalizing Dysfunction scale of the MMPI-2-RF, as well as with RCd-Demoralization, RC7-Dysfunctional Negative Emotions, NEGE-r-Negative Emotionality, and several specific facet scales. Surprisingly, the correlation with RC2-Low Positive Emotions, was not among the strongest, despite the fact that the PHQ-9 ostensibly targets this specific feature of depression (anhedonia). Substantial correlations with the somatic/cognitive scales of the MMPI-2-RF were also found. Implications for modified interpretation of the PHQ-9, and the need for more precise dimensional (rather than categorical) screening tools, are discussed.