Scientific background: PHQ-9
About this test
The PHQ-9 was developed by Spitzer, Kroenke, and Williams (1999) based on the DSM-IV criteria for major depression and is one of the most extensively studied screening instruments in clinical psychology and primary care. Numerous studies show good internal consistency (Cronbach's alpha usually above .85) as well as good sensitivity and specificity for detecting depressive disorders. The PHQ-9 is a screening and monitoring tool, not a diagnosis by itself — that always requires a clinical conversation.
Dimensions
Depression severity (total score)
Sum across all nine symptom items (0–27 points).
Sources & license
Kroenke, K., Spitzer, R. L., & Williams, J. B. W. (2001). The PHQ-9: Validity of a brief depression severity measure. Journal of General Internal Medicine, 16(9), 606–613.
The PHQ-9 is in the public domain and may be reproduced, translated, and used without permission.
https://www.phqscreeners.com