PHQ-9 Depression Severity

A PHQ-9 score of 10 or above is the standard clinical action threshold, with sensitivity and specificity of approximately 88% each for major depressive disorder. Below 10, the patient may have subthreshold depressive symptoms (5–9) requiring monitoring and low-intensity support. Above 10, active treatment (psychological therapy or medication) is indicated according to NICE CG90 guidelines.

NICE recommends repeat PHQ-9 at 2–4 weeks after starting antidepressants, as early response (defined as ≥20% reduction at 2–4 weeks) predicts eventual remission. For patients on psychological therapy (CBT), reassessment at 4–8 weeks is standard. Serial PHQ-9 monitoring every 4 weeks during active treatment phase is recommended. This is particularly important in the context of phq9 calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise phq9 computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.

Item 9 ('Thoughts that you would be better off dead or of hurting yourself') scoring ≥1 requires immediate clinical assessment, regardless of total PHQ-9 score. This includes a comprehensive risk assessment: ideation, plan, intent, access to means, previous attempts, protective factors, and social support. A safety plan must be created and documented. Never dismiss any positive response to item 9.

PHQ-9 is a screening and severity measurement tool, not a diagnostic instrument. A high score is not a diagnosis — it indicates high probability of depressive disorder and need for clinical assessment. Diagnosis requires a clinical interview assessing symptom duration (≥2 weeks), functional impairment, exclusion of organic causes (thyroid disease, anaemia, cancer), and differential diagnosis (bipolar disorder, grief reaction).

The PHQ-2 comprises just the first two items of the PHQ-9: anhedonia and depressed mood. A PHQ-2 score ≥3 has 83% sensitivity for major depression and is used as an ultra-brief screening tool in busy primary care settings. Patients who screen positive on PHQ-2 should proceed to full PHQ-9 assessment.

PHQ-9 was primarily validated in ambulatory general medicine and psychiatry populations. Somatic items (fatigue, sleep disturbance, appetite change) may be elevated by medical illness rather than depression, potentially inflating PHQ-9 scores in patients with chronic conditions. The PHQ-9 cognitive subscale (items 1, 2, 5, 6, 7, 9) is sometimes used to reduce somatic confounding in medically ill patients.

A ≥5-point reduction in PHQ-9 from baseline is considered a clinically meaningful response. Remission is generally defined as PHQ-9 <5. Response without remission (PHQ-9 reduced ≥50% but still ≥5) indicates partial response and may warrant treatment augmentation, dose increase, or switch to alternative antidepressant. This is particularly important in the context of phq9 calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise phq9 computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.

Yes — the PHQ-9 was designed for self-administration and is equally valid when completed by the patient without clinician administration. Patient self-completion in waiting rooms or via digital platforms (apps, online portals) allows efficient screening and monitoring. Self-administered PHQ-9 scores correlate well with clinician-administered versions in validation studies. This is particularly important in the context of phq9 calculations, where accuracy directly impacts decision-making. Professionals across multiple industries rely on precise phq9 computations to validate assumptions, optimize processes, and ensure compliance with applicable standards. Understanding the underlying methodology helps users interpret results correctly and identify when additional analysis may be warranted.