PHQ-9

Kroenke K, Spitzer RL, Williams JB. The PHQ-9: validity of a brief depression severity measure. The nine DSM-IV depression criteria rated 0–3; a score ≥ 10 had 88% sensitivity and 88% specificity for major depression, with 5/10/15/20 marking mild, moderate, moderately severe, and severe depression.

The PHQ-9 is recommended for depression screening and severity monitoring by the US Preventive Services Task Force framework and NICE; item 9 requires a direct safety assessment when endorsed. The instrument is free to use without permission (developed by Pfizer).