This Patient Health Questionnaire-4 (PHQ-4) is one of many scales modeled after the original PHQ measure. It is a valid four-item, composite measure that combines these two-item, ultra-brief scales: the Patient Health Questionnaire-2 (PHQ-2) to detect depressive disorders and the Generalized Anxiety Disorder-2 (GAD-2) to detect anxiety disorders.
The PHQ-4 is an four-item, ultra-brief screener for anxiety and depressive disorders. It is intended to be a short screening tool for both, given that anxiety and depressive disorders often co-occur.
Kroenke, K., Spitzer, R. L., Williams, J. B., & Löwe, B. (2009). An ultra-brief screening scale for anxiety and depression: The PHQ–4. Psychosomatics, 50(6), 613-621. https://doi.org/10.1016/S0033-3182(09)70864-3
Construct validity was demonstrated by comparing the PHQ-4 to the SF-20, demonstrating that increases in PHQ-4 scores were associated with increases in SF-20 scores (i.e., worsening functional status). Construct validity was further assessed by comparing the PHQ-4 to its component scales, the PHQ-8 (component depressive disorder scale) and the GAD-7 (component anxiety scale). Increases in level of severity reported on the PHQ-4, PHQ-8, and GAD-7 were all associated with worsening functional status (i.e., increases in mean disability days and mean physician visits reported). Additional information is available in Figure 1 and Table 2 of the source article.
Factorial validity was demonstrated by using principal-component analysis to assess the four items on the PHQ-4, demonstrating that the two depression items of the PHQ-2 and the two anxiety items of the GAD-2 explained 84% of the total variance. The anxiety items had the highest factor loadings for Factor 1 (anxiety) and the depression items had the highest factor loading for Factor 2 (depression). Additional information is available in Table 3 of the source article.
The PHQ-4 does not assess other conditions, such as suicidality and bipolarity, or the possibility of underlying medical condition(s) causing depression or anxiety symptoms. The responsiveness of the PHQ-4 for monitoring treatment needs to be determined in prospective trials. Emphasis should be placed on screening disorders independently.
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