Patient Health Questionnaire-9 (PHQ-9)

Overview

The Patient Health Questionnaire-9 (PHQ-9) is a 9-item self-report questionnaire that screens for depression and measures the severity of depressive symptoms over the preceding two weeks. Each item maps directly onto one of the nine DSM diagnostic criteria for major depressive disorder, which means the PHQ-9 doubles as both a severity measure and a rough diagnostic screen — a rare combination for an instrument this short.

It is one of the most widely used depression measures in the world, embedded in primary care templates, telehealth intake forms, and mental health treatment pathways across many countries, largely because it takes under three minutes to complete yet provides genuinely actionable clinical information.

History

The PHQ-9 was developed by Kurt Kroenke, Robert L. Spitzer, and Janet B.W. Williams and published in 2001 in the Journal of General Internal Medicine, building on the earlier PRIME-MD Patient Health Questionnaire the same team had validated in 1999. The goal was to take PRIME-MD’s diagnostic rigour — grounded directly in DSM criteria — and compress it into a fully self-administered tool that didn’t require a clinician-led interview to score or interpret.

The original validation study, conducted across thousands of primary care and obstetrics-gynaecology patients, demonstrated strong reliability and validity for both diagnosing and grading the severity of depression. That dual function — screen and severity scale in one — is a large part of why the PHQ-9 became a default choice in primary care and has remained one for over two decades.

Indications

The PHQ-9 is used wherever depressive symptoms need to be screened for, quantified, or tracked over time:

• Primary care and telehealth screening, often administered routinely alongside other intake questionnaires.
• Post-concussion and mild traumatic brain injury, where depressive symptoms are common and can significantly slow recovery if unaddressed.
• Chronic dizziness and vestibular disorders, where persistent, unpredictable symptoms are strongly associated with low mood and reduced quality of life.
• Chronic pain and long-term physical health conditions, where depression is a common but frequently under-recognised comorbidity.
• Monitoring treatment response, whether pharmacological, psychological, or lifestyle-based, through repeated administration over a course of care.

How It’s Scored

Each of the 9 items is rated on how often the symptom has bothered the respondent over the last two weeks, from 0 (not at all) to 3 (nearly every day). The total score is the sum of all 9 items, giving a range from 0 to 27.

Interpretation bands

The ninth item — “thoughts that you would be better off dead, or of hurting yourself in some way” — screens for passive or active suicidal ideation. Any response other than “not at all” on this item warrants prompt clinical attention, regardless of the total score. A person can score low overall and still endorse this item; the total is not a substitute for reviewing every item individually.

The original instrument also includes a non-scored functional-impact question about how difficult any endorsed problems have made work, home life, or relationships, which is useful context but isn’t part of the numeric total.

What It Tells the Clinician

• Screens and grades severity in one step. Because each item maps to a DSM criterion, the PHQ-9 gives a reasonable indication of both the presence and severity of a depressive episode from a single instrument.
• Surfaces risk that might not otherwise be volunteered. Item 9 is one of the few places in routine clinical screening where a patient is directly asked about self-harm thoughts — a question many people won’t raise unprompted.
• Adds a mood dimension to physical presentations. In vestibular, concussion, and chronic pain practice, the PHQ-9 helps identify when depression may be amplifying disability or slowing recovery, independent of — or interacting with — the primary physical diagnosis.
• Tracks response to treatment. Regular re-administration through a course of care gives an objective, comparable measure of whether mood is improving.
• Guides urgency of follow-up. A jump into the moderately severe or severe range, or any positive response on item 9, should change the immediate clinical priority regardless of what else is on the visit agenda.

References

1. Kroenke K, Spitzer RL, Williams JBW. The PHQ-9: validity of a brief depression severity measure. J Gen Intern Med. 2001;16(9):606-613.
2. Spitzer RL, Kroenke K, Williams JBW. Validation and utility of a self-report version of PRIME-MD: the PHQ primary care study. JAMA. 1999;282(18):1737-1744.