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PHQ-9: Interpreting a Positive Screen and a Changing Score

Interpret a PHQ-9 screen and changing score without confusing screening with diagnosis, percentage of baseline with improvement, or symptom severity with a safety assessment.

Quick Medical Calculator Editorial Team · Reading label · 2 min read

Retrospective study sequence, not publication date

Editorial record

This source-linked educational article has been updated through AI-assisted evidence checks and editorial review. Verify information against current guidance and local protocols before applying it to patient care.

Citation methodology

The PHQ-9 can support depression assessment and symptom monitoring. A total is not, by itself, a diagnosis or a medication prescription. This article does not reproduce the questionnaire; use an appropriate validated version for administration.

What the Number Means

The total ranges from 0 to 27. Common symptom-severity bands are 0-4, 5-9, 10-14, 15-19, and 20-27. In the original study, a cutoff of 10 had 88% sensitivity and 88% specificity against a structured interview in a subset of 580 participants. Those estimates are study results, not fixed performance guarantees in every language, age group, or setting. Kroenke and colleagues, 2001.

After a positive depression screen, assess symptoms, functional impairment, duration, other explanations, and the care the person needs. USPSTF screening recommendations depend on further evaluation and access to treatment and follow-up; they do not establish a universal annual screening or medication-titration schedule. USPSTF adult screening recommendation.

Worked Follow-Up: 16 to 9 Is Not a 56% Reduction

A fictional patient has a baseline score of 16 and a follow-up score of 9:

Reduction = (16 - 9) / 16 x 100 = 43.75%

The new score is 56.25% of baseline, which is different from a 56.25% improvement. If a service has prospectively chosen a 50% reduction as its response definition, this change does not meet that definition. It may still represent worthwhile improvement. Record the absolute fall of 7 points alongside the person's functioning, safety, adverse effects, and priorities. Do not automatically increase an antidepressant solely because a numerical target was missed.

Safety Is a Separate Assessment

An endorsement of the questionnaire's self-harm-related item requires direct clinical follow-up regardless of the total. Conversely, a low total or negative item does not rule out suicide risk when clinical concern remains. Current suicidal intent or immediate danger requires urgent emergency assessment; do not leave an imminently unsafe person alone. NIMH provides a structured clinician pathway for assessing positive suicide-risk screens, distinct from diagnosing depression. NIMH adult outpatient safety-assessment guide.

Match the Population

It is incorrect to say the PHQ-9 has never been validated below age 18: a primary study evaluated it in 442 adolescents aged 13-17. That does not make adult cutoffs or adult care pathways automatically appropriate for younger patients. Richardson and colleagues.