PHQ-9 Depression Calculator

The PHQ-9 calculator converts nine symptom-frequency responses into three displayed results, reproducing the PHQ-9 (Patient Health Questionnaire-9) validated by Kroenke, Spitzer, and Williams in a 2001 Journal of General Internal Medicine study. It first rounds every response to an integer and keeps it between 0 and 3, then adds the nine values. This creates a total score ranging from 0 to 27. Because the calculation is a plain sum, loss of interest, depressed mood, sleep difficulty, low energy, appetite change, negative self-view, concentration trouble, movement or restlessness, and self-harm thoughts each contribute the same number of points at the same response frequency. Severity is encoded in five steps.

Totals of 0–4 map to level 1, 5–9 to level 2, 10–14 to level 3, 15–19 to level 4, and 20–27 to level 5. The separate treatment-recommendation code uses broader breakpoints: level 1 below 10, level 2 from 10 through 14, and level 3 at 15 or above. Consequently, severity can change at 5 or 20 without changing that recommendation code. The output summarizes the entered responses; it does not diagnose depression, measure impairment, verify how long symptoms have persisted, or account for bereavement, physical illness, medication, substance use, bipolar-spectrum symptoms, or personal safety circumstances. The ninth response is included in the same arithmetic as every other item, so any self-harm concern requires human attention beyond what this numerical result can provide.