PHQ-9 is the Validated Tool of Choice for Depression Screening and Severity Assessment in Adults
Use the Patient Health Questionnaire-9 (PHQ-9) as your primary tool for both screening and assessing depression severity in adults. This recommendation is based on consistent guideline support and extensive validation across diverse populations 1.
Recommended Screening Approach
Initial Two-Question Screen (PHQ-2)
Start with the first two items from the PHQ-9 to efficiently identify patients who need full assessment 1:
- "Over the past 2 weeks, have you felt down, depressed, or hopeless?"
- "Over the past 2 weeks, have you felt little interest or pleasure in doing things?"
If either question scores ≥2 (occurring more than half the time or nearly every day), proceed to the full PHQ-9. This approach means only 25-30% of patients require the complete questionnaire 1.
Full PHQ-9 Administration
The PHQ-9 is a 9-item self-report scale assessing DSM-IV criteria for major depressive disorder 1. Use a cutoff score of 8 rather than the traditional 10 for cancer patients and potentially other medical populations, as this improves sensitivity while maintaining acceptable specificity 1.
Severity Interpretation
Score ranges indicate:
- 1-7: None to mild symptoms
- 8-14: Moderate symptoms
- 15-19: Moderate to severe symptoms
- 20-27: Severe symptoms 1
Alternative Tools for Specific Populations
While the PHQ-9 is preferred for general adults, consider these validated alternatives when clinically appropriate 1:
For Older Adults (≥65 years)
- Geriatric Depression Scale (GDS-15): 15-item version with cutoff ≥5 suggesting depression
- Avoids somatic symptoms that may confound diagnosis in medically ill elderly 1
For Pregnant and Postpartum Women
For Medically Ill Patients
- Hospital Anxiety and Depression Scale (HADS): Excludes physical symptom items that overlap with medical illness, with cutoff ≥8 on depression subscale 1
Critical Implementation Points
Always conduct diagnostic confirmation when moderate to severe symptoms are detected (PHQ-9 ≥8). Screening alone is insufficient—positive screens require structured clinical interview using DSM criteria to confirm diagnosis and assess suicide risk 1.
Address the suicide item carefully. Item 9 asks about self-harm thoughts. While some clinicians omit this, doing so artificially lowers scores and weakens predictive validity. Patients rarely endorse this item in isolation—it typically occurs with multiple other symptoms 1. Any positive response requires immediate risk assessment.
Rule out medical causes before attributing symptoms to primary depression. Medications (especially interferon), thyroid disorders, anemia, and other conditions can produce depressive symptoms 1.
Common Pitfalls to Avoid
The evidence shows screening only benefits patients when adequate systems exist for diagnosis, treatment, and follow-up 4, 2. Screening without these supports provides minimal benefit and may cause harm through false positives and unnecessary treatment 5.
Don't screen patients already diagnosed with or currently being treated for depression—this recommendation applies to previously undiagnosed individuals 5.
The PHQ-9 demonstrates sensitivity ranging 0.37-0.98 and specificity 0.42-0.99 across studies, with optimal performance using the two-stage approach described above 6. This wide range reflects different populations and cutoff scores, reinforcing the importance of using validated cutoffs for your specific patient population.