What your PHQ-9 score means, and what happens to it

you filled it in on a tablet, or on paper on a clipboard, or a nurse read the questions out. nine of them, about the last two weeks. now there is a number in your chart and nobody told you what it means or where it goes. this is that page.

the nine questions

the phq-9 asks how often, over the last two weeks, you have been bothered by each of nine things: little interest or pleasure in doing things; feeling down, depressed or hopeless; trouble sleeping or sleeping too much; feeling tired; poor appetite or overeating; feeling bad about yourself; trouble concentrating; moving or speaking slowly, or being fidgety and restless; and thoughts that you would be better off dead or of hurting yourself [2].

each answer scores 0 (not at all), 1 (several days), 2 (more than half the days) or 3 (nearly every day). the total runs 0 to 27 [2].

the bands

from the paper that validated the form in 2001, with 6,000 patients in fifteen clinics [1]:

ten is the usual cut-off for a positive screen. in that first study, a score of 10 or more had "a sensitivity of 88% and a specificity of 88% for major depression" [1].

ten is a flag, not a diagnosis

the biggest test of the form since then pooled 58 studies and 17,357 people. at 10 or more, against a clinician interview, the phq-9 caught 88% of people with major depression and cleared 85% of people without it [3]. that is a good screen.

it is not a diagnosis, and here is the arithmetic, which is ours: in 1,000 people of whom 150 have major depression, about 132 of them score 10 or more. so do about 128 of the 850 who do not. roughly half of positive screens are not major depression. the people who ran the 58-study analysis said the same thing in a second paper: questionnaires "are not designed to ascertain diagnostic status" and, when studies use them instead of interviews, they find depression in 31% of people rather than 17% [4].

so if your score was over nine, the honest next step is a conversation, not a label. and if your score was under ten, that is a negative screen, not proof that nothing is wrong; the form misses about one in eight people who do have depression [3].

question 9

the last item asks about "thoughts that you would be better off dead or of hurting yourself in some way" [2]. it is on the form so that it gets asked. any answer other than "not at all" should produce a conversation in the room, on the day, not a number in a file.

if you are having those thoughts now: in the us, call or text 988. it is free, it is open all the time, and you do not need a score to use it.

where your score goes

into your chart, and from there into quality reporting, which is the part nobody explains.

medicare's screening measure counts whether you were screened and, if the screen was positive, whether a follow-up plan was written within two days. a referral counts. a prescription counts. so does "other interventions or follow-up". the measure's own text warns clinicians to "only order pharmacological intervention when appropriate and after sufficient diagnostic evaluation" [7].

medicare's remission measure starts a clock when you have a diagnosis of major depression or dysthymia and a phq-9 over nine. it is met if your score is under five twelve months later [8]. health plans report a parallel set to ncqa, and one of those measures simply counts whether a phq-9 score is present in your record [9].

none of that is sinister. it does mean your score has a use to people other than you, and that the thing being counted is the number. the long version, including who paid for the form and what the money around it is, is in who wrote the phq-9, who paid for it, and who gets paid on your score.

the score by itself does nothing

sixteen randomised trials, 7,576 patients: giving clinicians a depression questionnaire result, on its own, changed depression outcomes not at all [5]. the us preventive services task force still recommends screening adults, because screening attached to follow-up does help [6]. the difference is what happens after the form.

in one randomised trial, clinicians used rating scales to guide each treatment decision at each visit. 73.8% of those patients reached remission, against 28.8% with usual care, and it happened in about half the time [10]. a review of 51 studies found the same pattern: frequent feedback of the score in the room helped; one-time screening did not [11].

five points

the medicare remission measure's own clinical text says "a five-point drop in PHQ-9 score is considered the minimal clinically significant difference" [8]. that is the number to hold onto. not whether you are over or under ten this visit, but whether the score moved five points since last time, and in which direction.

three questions that turn the form into care

these are questions, not advice. they cost nothing and nobody bills for them.

1. what is my number, and what was it last time?
2. what would we change if it has not dropped by five points?
3. is there someone whose job is to follow up on this, or does the form go in the file?

that is measurement-based care, which is the version of the questionnaire that the trials say works. you can ask for it yourself.

this page does not tell you to start, stop or change anything. a score is one input to a conversation with the person who prescribes for you, and it is a better input when you know what it is.

adam