PHQ-9: the most widely used mood questionnaire in primary care
The PHQ-9 asks nine questions about depressive symptoms over the last two weeks. It's one of the most studied screening tools in mental health, but it doesn't diagnose.
Where the scale comes from
The PHQ-9 is part of the Patient Health Questionnaire, developed by Robert Spitzer, Janet Williams and Kurt Kroenke in the 1990s to help primary care doctors recognize common mental health problems. The nine-item version was validated in 2001 (Kroenke, Spitzer & Williams, 2001).
Each question maps onto one of the nine diagnostic criteria for a depressive episode: little interest or pleasure, feeling down, sleep changes, tiredness, appetite changes, feeling bad about yourself, trouble concentrating, moving slowly or restlessly, and thoughts of death or self-harm. Answers range from 0 ("not at all") to 3 ("nearly every day"), for a total of 0 to 27. Scores of 5, 10, 15 and 20 mark mild, moderate, moderately severe and severe symptoms.
What the research says
In the original study of thousands of patients, a score of 10 or more had a sensitivity and specificity of about 88% for major depression (Kroenke et al., 2001). An individual participant data meta-analysis covering tens of thousands of people confirmed that 10 is a reasonable screening cut-off, with somewhat lower accuracy than the original study (Levis, Benedetti & Thombs, 2019).
The PHQ-9 is also used to track symptoms over the course of treatment. It has been validated in many countries and languages.
Limits of the scale
Screening is not diagnosis. Many people who score high don't have major depression when assessed by a professional, and symptoms like tiredness and sleep changes can have physical causes. The last item asks about thoughts of death or self-harm: any answer other than zero on that item deserves attention, whatever the total score.
Limitations
The result reflects only the last two weeks and depends on how you read each question. The scale doesn't assess bipolar disorder, grief or other conditions that can look like depression. A high score is not a diagnosis, and a low score doesn't rule out distress. If you recognize yourself in many items, talk to a health professional.
How Ethea adapts the model
Ethea presents the nine items with the original response options and adds up the points as in the publication, showing the reference ranges as guidance. Because the last item asks about thoughts of death, we show crisis support information alongside the scale. This questionnaire was not created by Ethea: credit goes to Kroenke, Spitzer and Williams.
Ethea is not affiliated with the scale's authors or with any institution that distributes it.
References
Links with a DOI go to the original article. Where no DOI is given, the link opens a Google Scholar search.
- Kroenke, K., Spitzer, R. L., & Williams, J. B. W. (2001). The PHQ-9: Validity of a brief depression severity measure. Journal of General Internal Medicine, 16(9), 606–613. DOI: 10.1046/j.1525-1497.2001.016009606.x(opens in a new tab)
- Levis, B., Benedetti, A., & Thombs, B. D. (2019). Accuracy of Patient Health Questionnaire-9 (PHQ-9) for screening to detect major depression: Individual participant data meta-analysis. BMJ, 365, l1476. DOI: 10.1136/bmj.l1476(opens in a new tab)
- Santos, I. S., Tavares, B. F., Munhoz, T. N., et al. (2013). Sensibilidade e especificidade do Patient Health Questionnaire-9 (PHQ-9) entre adultos da população geral. Cadernos de Saúde Pública, 29(8), 1533–1543. Search Google Scholar(opens in a new tab)