A nurse is conducting a depression screen at a primary care visit. Which validated tool is the most widely used for depression screening?

PHQ-9 (Patient Health Questionnaire-9): 9 questions about depressive symptoms over the past 2 weeks; each scored 0-3 (not at all to nearly every day); SCORES: 0-4 none/minimal; 5-9 mild; 10-14 moderate; 15-19 moderately severe; 20-27 severe; VALIDATED: Multiple clinical settings, populations, languages; recommended by USPSTF for routine screening in adults; SCREENING IS RECOMMENDED: USPSTF recommends depression screening for general adult population including pregnant and postpartum women; PHQ-2 (first 2 questions of PHQ-9) is used as ultra-brief screen — if positive, proceed to full PHQ-9; C-SSRS screens specifically for suicidal ideation, not depression broadly; Hamilton and BDI are clinician-administered or research-focused, less used in routine primary care.