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Research Instrument Mental Health & Mood // PHQ9

Patient Health Questionnaire-9

9-item depression screening tool measuring symptom severity over the past 2 weeks. Scores range from 0 to 27.

Purpose Details Scientific Documentation Limitations Related

Purpose

Self-report research instrument, reproduced here under an open license for non-diagnostic educational, research, and self-reflection use.

Details

Administration
Self-Administered
Intended Use
Research

Scientific Documentation

Developer / Author
Kroenke, K., Spitzer, R. L., & Williams, J. B.
Development Year
2001

Theoretical framework: Brief depression severity measure directly based on the nine DSM-IV depression diagnostic criteria.

Reliability: Original validation study reported high internal consistency (Cronbach's alpha = .89).

Validity: Extensively validated against structured clinical interviews; one of the most widely used depression screening tools worldwide.

References: Kroenke, K., Spitzer, R. L., & Williams, J. B. (2001). The PHQ-9: validity of a brief depression severity measure. Journal of General Internal Medicine, 16(9), 606-613.

Limitations: Imported from the OpenScales open item-bank project. This specific digital implementation has not been independently clinically validated by PsiQ — scores are for self-reflection, research, and educational purposes only, and are not a diagnosis.

License: Pfizer released all PHQ and GAD-7 screeners without copyright restriction (https://www.phqscreeners.com/); this OpenScales digital implementation is licensed CC BY 4.0. Citation: Kroenke, K., Spitzer, R. L., & Williams, J. B. (2001). The PHQ-9: validity of a brief depression severity measure. Journal of General Internal Medicine, 16(9), 606–613. This is not a diagnostic tool. If you are in crisis or having thoughts of self-harm, please contact a licensed mental health professional or a crisis helpline in your country immediately.

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