PHQ-9 explained: when a bad stretch becomes clinical depression

A bad week is not depression. A two-week stretch of low mood, broken sleep, and the kind of weight that makes brushing your teeth feel like work might be. The Patient Health Questionnaire (PHQ-9) is the nine-question tool clinicians around the world use to tell the difference.

This article walks through what each score band actually means, what the two-week clock is for, and when a number on a screen should turn into a phone call.

TL;DR

• PHQ-9 has nine questions matched to the nine DSM-5 criteria for major depressive disorder, scored 0 to 27.
• A score of 10 or higher is the threshold for further clinical evaluation, validated in 17,000+ patients by Levis 2019.
• Bands: 0-4 minimal, 5-9 mild, 10-14 moderate, 15-19 moderately severe, 20-27 severe.
• The 2-week window matters. PHQ-9 asks about the past 14 days, mirroring the DSM-5 minimum duration for a depressive episode.
• Item 9 (thoughts of self-harm) is acted on regardless of total score. Any positive answer = same-day clinical contact.
• For teens 13-17, the cutoff shifts up to 11 (Richardson 2010 in Pediatrics).
• US crisis line: 988 (Suicide and Crisis Lifeline).

What the PHQ-9 is, and why it exists

Robert Spitzer and Kurt Kroenke published the PHQ-9 in 2001 in the Journal of General Internal Medicine. Their goal was modest and practical: a 9-question screen that a primary-care nurse could hand a patient in the waiting room, get back in under 3 minutes, and use to decide whether the appointment needed a 30-minute mental-health conversation or not.

The questions track the nine DSM-IV criteria for major depressive episode, one-to-one. Each is rated 0 (not at all) to 3 (nearly every day) for the past 2 weeks. The total runs 0 to 27.

Kroenke’s original 2001 study validated it against the structured clinical interview in 6,000 primary-care and obstetric patients. The threshold of 10 caught 88% of true major-depression cases and ruled out 88% of patients who did not have it. Twenty years later, Levis 2019 in the BMJ pulled together individual data from 58 studies and 17,357 patients and confirmed the same: at PHQ-9 ≥ 10, sensitivity is 0.88 and specificity is 0.85. The number has held.

The 2-week clock

The questionnaire opens with: “Over the last 2 weeks, how often have you been bothered by any of the following problems?”

That fortnight is not arbitrary. DSM-5 requires symptoms to be present for at least 2 consecutive weeks before a major depressive episode can be diagnosed. The PHQ-9 is built around that floor. A week of sadness after a breakup, a rough Monday after a sleepless weekend, the low couple of days that follow a stomach bug — none of these are what the questionnaire is built to measure.

Two weeks is also where the math of natural mood variation runs out. Most people swing through a few bad days a month. Sustained low mood, sustained sleep change, sustained loss of interest, lasting fourteen days in a row, is not the same thing.

What each band actually means

Kroenke 2001 proposed the now-standard scoring bands, and Manea 2012 in CMAJ meta-analytically tightened them:

These are statistical bands, not diagnostic labels. A 14 does not mean “you have moderate depression.” It means “your symptoms cluster the way moderate depression clusters.” The interview, the history, the timeline — those decide what the score means for you.

NIMH summarises it the same way on its depression topic page: the questionnaire is a screen, not a diagnosis.

Item 9: the question that floats free of the total

The ninth question asks: “Thoughts that you would be better off dead, or of hurting yourself in some way.”

Any answer above zero — even “several days” — is treated as a safety signal independent of the rest. A score of 4 on the full PHQ-9 with a 1 on item 9 is acted on differently than a score of 4 with a 0. Kroenke 2001 designed it deliberately so that suicidality could not be diluted by other items.

If you answer above zero, two paths are standard practice:

1. Same-day contact with your GP or your existing therapist.
2. Or, if “today” feels too unstable, the 988 Suicide and Crisis Lifeline — call or text 988 in the US. The line is staffed 24 hours.

The point is not that thoughts of self-harm mean you are about to act. Most people who have those thoughts at some point in their life never do. The point is that the question is the one most worth not sitting on.

What “moderate” looks like in practice

A PHQ-9 of 12 (low end of moderate) maps to a person who, over the past 2 weeks:

• Sleeps badly most nights (item 3 scored 2 or 3).
• Feels tired most days (item 4 scored 2 or 3).
• Has lost some interest in things that used to feel good (item 1 scored 2).
• Notices their mood is low most days (item 2 scored 2).
• Has some trouble concentrating at work or school (item 7 scored 1 or 2).
• Items 5, 6, 8, 9 may be at 0 or 1.

That cluster is what the threshold of 10 is catching. It is not “everyone has bad days.” It is a 2-week stretch where most of the boxes that DSM-5 calls major-depressive episode are at least partially ticked.

When the PHQ-9 is misleading

Three situations push the score around without the underlying clinical picture matching:

Acute grief. In the first 2 to 6 weeks after a significant loss, PHQ-9 scores rise the same way they would for primary depression. DSM-5 removed the “bereavement exclusion” in 2013, so the score will not auto-correct for it. The clinical interview does.

Physical illness with overlapping symptoms. Hypothyroidism, anaemia, sleep apnoea, B12 deficiency — each can score the somatic items (sleep, energy, appetite) without low mood being primary. A high PHQ-9 in someone who has not had a basic blood panel in a year is a flag to do the blood panel first.

Single bad week inside a normal year. The 2-week window is a floor, not a ceiling. If you took PHQ-9 on the worst Tuesday of an otherwise stable year, you might score 12 today and 4 next month. Re-testing in 2 to 3 weeks separates a bad fortnight from a depressive episode.

The PHQ-9 number is data, not a verdict.

What to do with your number

• 0-9. No action beyond noticing. If life context (a divorce, a job loss, a move) makes the score feel light, that context matters more than the score.
• 10-14. Book a GP appointment within 1-2 weeks. Bring the score. Ask about a referral to psychotherapy and whether your context suggests medication.
• 15-19. Book within the week. Be honest about item 9. Most GPs at this band recommend both therapy and an SSRI conversation.
• 20-27. Same-week appointment. If item 9 is above zero, same-day contact (GP or 988).

If your score is 10+ and you also have anxiety symptoms, the matched GAD-7 is the parallel tool. Many people who screen positive on PHQ-9 also screen positive on GAD-7. Take both, bring both.

You can take the PHQ-9 itself here, in your browser, with nothing saved: PHQ-9 depression screener.

Worth remembering

A bad fortnight is not the same thing as depression, and a high PHQ-9 score is not a diagnosis. But the questionnaire is good at one specific job: telling the difference between mood you can ride out and mood that benefits from a conversation with someone trained.

Ten or higher, for two weeks or longer, is the line. Item 9, any value above zero, is its own line and does not wait for the total. The rest is what the appointment is for.