Patient Health Questionnaire (PHQ-9)

The PHQ-9 (Patient Health Questionnaire-9) is a brief, 9-item self-report questionnaire that is widely used and validated, designed specifically for screening, diagnosing, and monitoring the severity of major depressive disorder. It is one of the most common tools in primary care and mental health settings. Each of the 9 items corresponds directly to the 9 DSM-IV/DSM-5 diagnostic criteria for major depressive disorder. Patients are asked to rate the frequency with which they have been bothered by each symptom over the last two weeks, using a 4-point scale (0="Not at all", 1="Several days", 2="More than half the days", 3="Nearly every day"). The total score is calculated by summing the points for all 9 items, ranging from 0 to 27. This total score is used to classify depression severity: 0-4 (minimal or none), 5-9 (mild), 10-14 (moderate), 15-19 (moderately severe), and 20-27 (severe). In addition to the total score, the PHQ-9 includes a tenth item (often unscored in the total but crucial) that assesses for suicidal ideation (Item 9: "Thoughts that you would be better off dead, or of hurting yourself in some way"). Any positive response on this item (anything above "0") requires immediate safety assessment by a clinician. The tool is used not only for initial screening but also for monitoring treatment response over time.