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Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines, so you may find the language more technical than the condition leaflets.
This easy to use patient questionnaire is a self-administered version of the PRIME-MD diagnostic instrument for common mental disorders.[1] The PHQ-9 is the depression module, which scores each of the nine DSM-IV criteria as "0" (not at all) to "3" (nearly every day). It has been validated for use in primary care.[2]
It is not a screening tool for depression but it is used to monitor the severity of depression and response to treatment. However, it can be used to make a tentative diagnosis of depression in at-risk populations - eg, those with coronary heart disease or after stroke.[3, 4]
When screening for depression the Patient Health Questionnaire (PHQ-2) can be used first (it has a 97% sensitivity and a 67% specificity).[5]If this is positive, the PHQ-9 can then be used, which has 61% sensitivity and 94% specificity in adults.
PHQ-9 Depression Severity Scores represent: 0-4 = none, 5-9 = mild, 10-14 moderate, 15-19 moderately severe, 20-27 severe.