The depression questionnaire was paid for by a drug company, and the form says so
The PHQ-9 footer reads: "Developed by Drs. Robert L. Spitzer, Janet B.W. Williams, Kurt Kroenke and colleagues, with an educational grant from Pfizer Inc." The 2001 validation paper says the same.
We have not finished checking this source. No judgement either way. how we score evidence
Caveat on this rating: Funding a tool is not the same as biasing it: the PHQ-9's accuracy has since been tested in an independent individual-participant meta-analysis of 58 studies (stop 2), and the tool is free precisely because of the grant. What the grant bought is reach, not a rigged score. The GAD-7 funding statement was read from the instrument's own attribution, not from the 2006 paper's text.
You have probably filled it in. Nine questions, each scored 0 to 3, about the last two weeks. Its name is the PHQ-9, and the small print at the bottom of the form is the most honest thing about it.
Significant findings
The footer on the instrument reads: "Developed by Drs. Robert L. Spitzer, Janet B.W. Williams, Kurt Kroenke and colleagues, with an educational grant from Pfizer Inc. No permission required to reproduce, translate, display or distribute." The 2001 paper that validated it, in the Journal of General Internal Medicine, says it in the acknowledgments: "The development of the PHQ-9 was underwritten by an educational grant from Pfizer US Pharmaceuticals, New York, NY." The instrument reproduced in that paper's appendix carries the line "Copyright 1999 Pfizer Inc. All rights reserved."
The validation itself was large: 3,000 patients across 8 primary care clinics and 3,000 across 7 obstetrics-gynecology clinics, with 580 interviewed by a mental health professional. From that work came the cut-points still used today: "PHQ-9 scores of 5, 10, 15, and 20 represented mild, moderate, moderately severe, and severe depression, respectively", and at a score of 10 or more "a sensitivity of 88% and a specificity of 88% for major depression."
The anxiety scale that usually rides beside it, the GAD-7, was built by the same group and carries the same footer, word for word. Its 2006 validation ran in 15 primary care clinics, with 2,740 patients completing the questionnaire and 965 interviewed; the cut point of 10 gave sensitivity 89% and specificity 82%.
Two things are true at once. Pfizer paid for the tools, and Pfizer sold Zoloft; the library's chemical-imbalance trail quotes its 2004 advertisement. And the same grant is why the tools are free: no licence, no fee, no permission needed, which is a large part of why every clinic, app and payment measure in this trail uses them rather than a scale someone charges for.
Worth asking
The form does not hide who paid for it. The question this trail follows is what happened next: how a free, industry-funded screening tool became the number that clinics, health plans and Medicare are paid on.
Source
The PHQ-9: validity of a brief depression severity measure — Kroenke K, Spitzer RL, Williams JB (2001)
Read the source: https://doi.org/10.1046/j.1525-1497.2001.016009606.x
DOI: 10.1046/j.1525-1497.2001.016009606.x
How this was scored
- Study design
- not recorded
- Funding
- not recorded
- Published in
- not recorded
- Sample size
- not recorded
- Preregistered
- not recorded
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
We have not finished checking this source, so there is no scoring to show yet. “We have not checked this yet” and “this is disputed” are different statements, so no scored band is shown rather than a low one.
Read the full scoring rubric, including what it can't tell you.
Published September 15, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "not yet assessed". We have not finished checking this source. No judgement either way. One caveat travels with that badge: Funding a tool is not the same as biasing it: the PHQ-9's accuracy has since been tested in an independent individual-participant meta-analysis of 58 studies (stop 2), and the tool is free precisely because of the grant. What the grant bought is reach, not a rigged score. The GAD-7 funding statement was read from the instrument's own attribution, not from the 2006 paper's text. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
The PHQ-9: validity of a brief depression severity measure — Kroenke K, Spitzer RL, Williams JB (2001). DOI: 10.1046/j.1525-1497.2001.016009606.x. The full source is linked on this page so you can read it yourself.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.