Hong Life CalculatorsUnderstanding the PHQ-9 depression screening score — concept and principle
The Patient Health Questionnaire-9 (PHQ-9) is a nine-question self-report tool for depression. Each question matches one of the nine symptom criteria for major depression in the DSM, and you rate how often each one has bothered you over the last two weeks. Doctors use it to screen for depression, to gauge its severity and to track how symptoms change during treatment. It is free to use and has been translated and validated in many languages, including Korean.
How it is calculated
Each item is scored 0 (not at all), 1 (several days), 2 (more than half the days) or 3 (nearly every day). The total is the simple sum:
PHQ-9 = item 1 + item 2 + … + item 9, range 0–27.
- 0–4 minimal; 5–9 mild; 10–14 moderate; 15–19 moderately severe; 20–27 severe.
- Item 9 (thoughts of being better off dead or of self-harm) is shown separately, because any answer above 0 needs attention whatever the total.
The principle
Depression is diagnosed from a pattern of symptoms that persists for at least two weeks. The PHQ-9 turns that pattern into a number: the more symptoms you have and the more often you have them, the higher the score. In the original validation study by Kroenke, Spitzer and Williams, a score of 10 or more identified major depression with a sensitivity and specificity of about 88% each, which is why 10 is the most common cut-off for further assessment. Items 1 and 2 on their own form the shorter PHQ-2.
Worked example
- Inputs: all nine items answered "Not at all (0)".
- Total = 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 0.
- 0 is below 5, so severity is minimal.
- Item 9 is 0, so no item 9 warning is shown: —.
How to read the result
Scores below 5 suggest few depressive symptoms. Scores of 10 or above are a reason to see a doctor or mental health professional, who will ask about duration, daily functioning and other causes such as thyroid disease, medicines or grief. When the questionnaire is repeated, a fall of 5 points or more is often treated as a clinically meaningful improvement. If item 9 is above 0, talk to someone today, regardless of the total.
Common mistakes
- Answering about how you feel today instead of over the past two weeks.
- Treating a single high score as a diagnosis of depression.
- Ignoring item 9 because the total looks low.
Frequently asked questions
Can I take the PHQ-9 again?
Yes. Clinicians often repeat it every few weeks to see whether treatment is working.
Does a low score mean I am fine?
It means few symptoms right now. If you still feel unwell, speak to a doctor anyway.
Is the PHQ-9 suitable for teenagers?
Adapted versions exist for adolescents; follow the advice of a paediatric or school health professional.
Sources: Kroenke K, Spitzer RL, Williams JBW, The PHQ-9: validity of a brief depression severity measure, Journal of General Internal Medicine 2001