PHQ-9 (Patient Health Questionnaire)
Depression severity screening and monitoring tool
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Why use it
Brief, validated, freely available screening tool for depression. Recommended by USPSTF for routine depression screening. Can monitor treatment response with serial administration. Maps directly to DSM-5 criteria.
About
The PHQ-9 is a self-administered 9-item questionnaire based on DSM criteria for major depressive disorder. Each item is scored 0-3, yielding a total score of 0-27. It serves dual purposes: screening for depression and monitoring treatment response over time. It is one of the most widely validated depression instruments globally.
When to use
- Routine depression screening in primary care
- Monitoring treatment response (repeat every 2-4 weeks)
- Initial psychiatric assessment
- Pre-surgical psychological evaluation
- Research and clinical trials
Formula
Pearls & pitfalls
- ALWAYS assess item 9 (self-harm/suicidal ideation) independently — any positive response requires safety evaluation.
- A score ≥10 has sensitivity of 88% and specificity of 88% for major depression.
- A 5-point change is considered clinically significant for treatment monitoring.
- PHQ-9 can be falsely elevated in patients with chronic pain, fatigue-related conditions, or medical illness.
- PHQ-2 (items 1-2 only) can be used as an ultra-brief screen — score ≥3 warrants full PHQ-9.
- Available in over 70 languages; freely reproducible without permission.
Next steps
Score 5-9: watchful waiting, repeat PHQ-9 at follow-up. Score 10-14: consider counseling and/or pharmacotherapy. Score 15-19: active treatment with antidepressant and/or psychotherapy recommended. Score 20+: aggressive treatment; consider psychiatric referral. Always assess item 9 (self-harm) regardless of total score.
Evidence
Validated in >6,000 patients across primary care and obstetrics. Sensitivity 88%, specificity 88% for MDD at cutoff ≥10. USPSTF recommends depression screening in adults (Grade B). Widely adopted globally as the standard screening tool.