PHQ-9: Depression Severity and Screening
The PHQ-9 scores the nine DSM criteria for depression over the past two weeks. It works both as a screen and as a severity measure, which is unusual.
Patient Health Questionnaire-9 (PHQ-9)
The Patient Health Questionnaire-9 is a nine item self-report measure that scores each DSM criterion for major depressive disorder over the previous two weeks. It functions as a screening tool and as a severity measure sensitive enough to track treatment response, and it is free to use.
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Disease
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What is the PHQ-9
The PHQ-9 asks how often, over the last two weeks, the person has been bothered by each of the nine symptoms that define major depressive disorder, from little interest or pleasure through to thoughts of being better off dead. Each item scores zero to three, giving a total from zero to 27. A tenth question, scored separately, asks how difficult those problems have made daily functioning.
Its usefulness comes from doing two jobs well. Most instruments either screen or grade severity; the PHQ-9 maps directly onto diagnostic criteria while producing a continuous score responsive enough to follow treatment. It is also short, self-administered and free of licence fees, which is why it appears in primary care, specialist services and trials alike.
Total scores of 5, 10, 15 and 20 mark the thresholds for mild, moderate, moderately severe and severe depression. A score of 10 or above is the most commonly used screening cut-off. A change of about five points is generally treated as clinically meaningful, though the figure varies by baseline severity.
Item nine asks about thoughts of self-harm or being better off dead, and any study or service deploying the PHQ-9 digitally needs a defined response pathway before the first questionnaire is sent: who is alerted, how quickly, and what the respondent sees on screen. A screening instrument without a route to support is not a neutral act.
Advantages
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Measures healthcare intervention results systematically.
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Streamlines research data gathering process.
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Provides consistent measurements for clinical research.
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Related Instruments
Digital counterpart
Digital biomarkers that measure the same thing with sensors rather than a questionnaire.
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