Analysis and Purpose of the Questionnaire

The Patient Health Questionnaire [PHQ-4] was developed by Kroenke and colleagues in 2009 and is one of the most widely used screening tools for depression. It can also be used within the framework of a diagnostic algorithm to suggest a possible diagnosis, as an instrument for assessing disease severity, and as a tool for monitoring treatment response.

Scoring of Questions

The PHQ-4 self-report questionnaire consists of 4 questions answered on a 4-point Likert-type scale. This questionnaire allows for accurate measurement of the core symptoms/signs of depression and anxiety by combining the two-item depression scale (PHQ-2), which assesses the main criteria for depression, with the two-item anxiety scale (GAD-2).

Statistical Analysis

The PHQ-4 provides an overall score from its subscales that reflects symptom burden, functional impairment, and disability. An elevated PHQ-4 score is not diagnostic but instead indicates the need for further evaluation to determine the presence or absence of a clinical disorder that would justify treatment.

Validity and Reliability

In terms of validity, the PHQ-4 is a reliable and valid tool with high internal consistency (α = 0.81), meaning that it can serve as a diagnostic indicator for depression and anxiety in young adults.

References

Kroenke, K., Strine, T. W., Spitzer, R. L., Williams, J. B., Berry, J. T., & Mokdad, A. H. (2009). The PHQ-8 as a measure of current depression in the general population. Journal of Affective Disorders, 114(1–3), 163–173.