Patient Health Questionnaire (PHQ-9)
The Patient Health Questionnaire (PHQ-9) is a nine-item instrument designed for use in primary care settings (Kroenke, Spitzer & Williams., 2001).
It is based directly on the diagnostic criteria for major depressive disorder in the Diagnostic and Statistical Manual, Fourth Edition (American Psychiatric Association, 2000).
Items are rated for the last two weeks, using a four-point scale for duration (from “not at all” to “nearly every day”). The PHQ-9 has been adopted widely as a screening and diagnostic tool as well as a measure for monitoring treatment.