Internal Structure of the Patient Health Questionnaire-9: A Systematic Review and Meta-analysis.

Area of Science:

• Psychometrics
• Mental Health Assessment
• Clinical Psychology

Background:

• The Patient Health Questionnaire-9 (PHQ-9) is a widely used self-administered tool for depression screening.
• Evaluating the psychometric properties of health instruments is crucial for reliable assessment.

Purpose of the Study:

• To systematically review and evaluate the internal structure of the PHQ-9.
• Assessing structural validity, internal consistency, and measurement invariance of the PHQ-9.

Main Methods:

• Systematic review using the updated COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) methodology.
• Searched major databases (PubMed, Embase, CINAHL, PsycINFO, Cochrane Library) up to February 28, 2023.
• Included 98 psychometric studies from 90 reports across 40 countries.

Main Results:

• Reviewed studies identified various PHQ-9 factor structures, with the one-factor model showing strong evidence.
• Sufficient high-quality evidence supports the one-factor structure's validity, internal consistency (Cronbach's α = .85), and measurement invariance across demographic groups.
• The PHQ-8 (excluding item 9) also demonstrated good structural validity, internal consistency (α = .76-.92), and measurement invariance across sex.

Conclusions:

• The one-factor PHQ-9 and PHQ-8, using a four-point Likert scale, exhibit the best internal structure based on current evidence.
• The aggregated total scores of the one-factor PHQ-9 and PHQ-8 are justified for use in practice and research.
• The PHQ-9's total score is suitable for comparing depression levels across demographic groups due to established measurement invariance.