SOURCE: PHQ-9, an evidence-based screening tool
The Patient Health Questionnaire-9, or PHQ-9, is a screening tool widely used by health professionals. It was scientifically developed and clinically validated in numerous studies. The PHQ-9 was originally developed by Drs. Robert L. Spitzer, Janet B.W. Williams, Kurt Kroenke and colleagues and is copyright 1999 Pfizer.